Description:FIELD OF THE DISCLOSURE
The present disclosure relates to mesoporous bioactive glass nanoparticles. More particularly, it relates to silver-incorporated mesoporous bioactive glass nanoparticles and a process for their preparation. The disclosure further relates to the silver-incorporated mesoporous bioactive glass nanoparticles exhibiting antibacterial activity, enhanced bioactivity, and favourable interactions with osteogenic and angiogenic cell systems, and to incorporation thereof in biomedical devices.
BACKGROUND
Mesoporous bioactive glasses (MBGs) are widely recognized as a significant development in the field of biomaterials. Their distinguishing features include a highly ordered porous architecture, large specific surface area, and narrow pore size distribution, all of which contribute to rapid formation of hydroxy-carbonate apatite (HCA) when exposed to simulated body fluid. These characteristics make MBGs superior to conventional melt-derived bioactive glasses, particularly in applications that demand strong tissue bonding, controlled degradation, or ion/drug release capability.
Conventionally, MBG compositions have been based on the ternary or quaternary SiO₂–CaO–P₂O₅ systems. In nearly all reported studies, phosphorus pentoxide (P₂O₅) has been regarded as an indispensable component, primarily because it promotes the nucleation of apatite phases during in-vitro bioactivity studies. Consequently, the phosphorus content in MBGs has traditionally been kept constant at approximately 5–10 mol%, particularly in the archetypal 58S composition (58 mol% SiO₂, 36 mol% CaO, 6 mol% P₂O₅). Against this fixed phosphorus background, researchers have attempted to improve MBG functionality by adding therapeutic ions such as silver, zinc, strontium, copper, magnesium, cobalt, and iron. Each of these ions has been reported to contribute certain desirable attributes: silver for antibacterial activity, zinc and strontium for osteogenesis, copper and cobalt for angiogenesis, and magnesium or iron for bioactivity modulation.
While such a strategy of retaining phosphorus and adding new dopants has been widely explored, it has several intrinsic disadvantages. The most common limitation arises from the reduction in surface area and pore volume that follows dopant incorporation. The introduction of multivalent ions into a phosphorus-retained Si–Ca–P network often disturbs the silicate structure, leading to partial collapse of mesopores or densification of the glass. Since high surface area and porosity are central to HCA formation, such structural losses directly translate into weaker bioactivity.
Another drawback is the restricted range of dopant incorporation. When dopant levels exceed a narrow threshold, the glass network tends to destabilize, resulting in unwanted crystallization or phase separation. This has limited the capacity of prior MBGs to achieve high loading of functional ions without sacrificing textural properties or stability.
Furthermore, the insistence on keeping phosphorus fixed has created a form of design rigidity in MBG research. Because phosphorus is assumed to be mandatory, little effort has been made to investigate whether partial or complete substitution of phosphorus with other functional ions could deliver equivalent or even superior performance. This has prevented systematic exploration of alternative compositions that might combine multiple functionalities in a single system.
The biological trade-offs in phosphorus-retained doped MBGs also remain problematic. For example, silver addition provides strong antibacterial effects but, in some cases, has been shown to compromise osteogenic responses when incorporated in phosphorus-fixed matrices. Similarly, copper may stimulate angiogenesis, but high copper levels often reduce biocompatibility when phosphorus is present. As a result, achieving a truly multifunctional MBG-combining antibacterial, osteogenic, and angiogenic characteristics in one material-has been elusive within the prior art framework.
In addition to compositional issues, the processing methods commonly adopted in earlier work introduce further limitations. Template removal has typically been achieved through high-temperature calcination, which eliminates surfactant residues but simultaneously destroys silanol (–Si–OH) groups from the surface. Such silanol groups are critical for initiating HCA nucleation and also serve as functional sites for drug loading or biomolecule attachment. Their loss diminishes the bioactivity and multifunctionality of the final MBG product.
Taken together, such disadvantages show that the conventional strategy—fixing phosphorus content and adding new dopants—suffers from inherent weaknesses in structure, compositional flexibility, multifunctionality, and processing. There exists, therefore, a need for an alternative approach in which phosphorus is not rigidly maintained but may be systematically substituted with functional ions such as silver. Such a strategy would not only preserve or even enhance the desirable mesoporous architecture but also provide new pathways to achieve antibacterial activity, osteogenic support, and angiogenic potential in a single composition.
Therefore, there exists a need for developing alternatives to get rid of aforementioned issues.
OBJECTS OF THE EMBODIMENT
An object of the present disclosure is to provide mesoporous bioactive glass nanoparticles (MBGs) in which phosphorus is not rigidly fixed but is systematically substituted with silver, thereby overcoming the design limitations of phosphorus-retained doped MBGs.
Another object of the present disclosure is to provide a composition of MBG nanoparticles based on SiO₂–CaO–P₂O₅, wherein a portion of P₂O₅ is substituted with Ag₂O, yielding nanoparticles with high surface area, tunable porosity, and enhanced functional properties.
Another object of the present disclosure is to provide a process for preparing silver-incorporated MBG nanoparticles using an acid-assisted sol–gel route combined with evaporation-induced self-assembly, followed by a two-step template removal method involving acid and ethanol extraction, which avoids high-temperature calcination and retains surface silanol groups.
Another object of the present disclosure is to provide MBG nanoparticles that exhibit multifunctional properties, including such as but not limited to antibacterial activity against both Gram-positive and Gram-negative microorganisms, enhanced in-vitro bioactivity through hydroxy-carbonate apatite (HCA) formation, and favourable interactions with osteogenic and angiogenic cell systems.
Another object of the present disclosure is to provide biomedical devices including such as but not limited to implants, scaffolds, coatings, or fillers incorporating the silver-incorporated MBG nanoparticles, thereby expanding the applicability of the material beyond nanopowder form.
Yet another object of the present disclosure is to develop a unified process for the preparation and standardization of multifunctional mesoporous bioactive glass nanoparticles with silver substitution for phosphorus, yielding materials with high structural stability, superior textural properties, antibacterial effectiveness, and biocompatibility suitable for biomedical device integration.
SUMMARY
In one aspect, the disclosure provides mesoporous bioactive glass nanoparticles comprising silica (SiO₂) in the range of 55–65 wt%, calcium oxide (CaO) in the range of 30–40 wt%, and a combined amount of phosphorus pentoxide (P₂O₅) and silver oxide (Ag₂O) in the range of 2–10 wt%, wherein phosphorus pentoxide is partially substituted with silver oxide in the range of 0.5–5 wt% relative to the total composition. The substitution functions as a network modifier that preserves mesoporous architecture, generates non-bridging oxygens and surface silanol groups, and stabilizes pore structure through local free volume. As a result, the nanoparticles combine structural stability with antibacterial functionality, ion release capability, and features conducive to bioactivity and material–tissue integration.
In another aspect, the disclosure provides a process for preparing the mesoporous bioactive glass nanoparticles. The process comprises dissolving a surfactant in ethanol and water, sequentially adding tetraethyl orthosilicate (TEOS), calcium acetate, triethyl phosphate, and silver acetate in amounts sufficient to yield the desired composition, inducing hydrolysis and condensation under acid-assisted sol–gel conditions, subjecting the sol to evaporation-induced self-assembly and aging, drying to obtain a gel, and removing the surfactant through a two-step method involving acid treatment followed by ethanol extraction. This process enables the controlled incorporation of silver oxide in place of phosphorus pentoxide while maintaining mesoporosity and surface characteristics essential for bioactivity.
In yet another aspect, the disclosure provides biomedical devices comprising the mesoporous bioactive glass nanoparticles. The nanoparticles, by virtue of their mesoporous architecture, surface silanol groups, and silver ion release, provide antibacterial functionality, support hydroxy-carbonate apatite nucleation, and contribute to favourable material–tissue interactions. The devices may take the form of scaffolds, bone fillers, polymer–ceramic composites, or coatings on orthopaedic and dental implants, thereby extending the applicability of the mesoporous bioactive glass nanoparticles to a wide range of biomedical applications.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features, and advantages of the embodiment will be apparent from the following description when read with reference to the accompanying drawings. In the drawings, wherein like reference numerals denote corresponding parts throughout the several views:
Referring to Figures 1A-1J, show morphological micrographs of pristine 58S MBG FESEM (left panel: 1A-1E) and HRTEM (right panel: 1F-1J) having (a) 0.0, (b) 0.5, (c) 1.0, (d) 1.5, and (e) 2.0 mole % Ag;
Referring to Figures 2A-2B, show nitrogen adsorption-desorption technique measurement on pristine 58S MBG nanoparticles with increasing Ag (mol %) (a) Isotherm plot, (b) Pore size distribution;
Referring to Figures 3A-3B, show degradability study of structural and local atomic architecture demonstrating (3A) HR-XRD plot and (3B) FTIR spectra of silver incorporated 58S MBG samples (0.0, 0.5, 1.0, 1.5, and 2.0) for 7 days of SBF soaking, respectively.
Referring to Figures 4A-4E, show (4A) ion-exchange kinetics study with different immersion times of 1, 4 and 7 days of synthesised Ag-doped 58S-MBG samples (0.0, 0.5, 1.0, 1.5, and 2.0), and (4B-4E) FESEM micrographs of 2 mole% % Ag incorporated 58S-MBG samples after 7 days of SBF immersion at different scales;
Referring to Figure 5, shows EDAX elemental mapping investigations of 58S MBG with 2.0 % Ag 58S-MBG after 7 days of SBF soaking;
Referring to Figures 6A-6C, show microbiological assay (Kirby-Bauer method) of MBGs with silver doping at different Mole% (0.0, 0.5, 1.0, 1.5, and 2.0) against E. coli;
Referring to Figures 7A-7B, show Bacteria susceptibility test using broth microdilution method: different two-fold serial dilutions starting from 500µg/mL of different Silver-doped MBGs (0.5, 1.0, 1.5, and 2.0 mole% Ag) against (7A) Staphylococcus aureus and (7B) Escherichia coli;
Referring to Figures 8A-8H, show cells attachment viability (8A-8D) SaOS2 cells and (8E-8H) H9C2 on different Ag doped MBGs (0.5, 1.0, 1.5, and 2.0 mole % Ag-MBGs) at different concentrations 5µg/mL, 10µg/mL, 20µg/mL, 50µg/mL, and 100 µg/mL;
Referring to Figures 9A-9F, show Haemolytic response of red blood cells (RBCs) to silver-doped mesoporous bioactive glasses (Ag-MBGs). (9A-9E) Percentage of haemolysis of RBCs incubated with different Silver-doped MBGs samples (0.0, 0.5, 1.0, 1.5, and 2.0 Mole% Ag) at different concentrations ranging from 2 to 400 µg/mL for 4 h. (9F) Images of suspension of RBCs in the presence of different Silver-doped MBGs, D-PBS (-) and Water (+) are used as negative (no haemolysis) and positive (haemolysis) controls, respectively. From left to right, (-), (+), and 0.0, 0.5, 1.0, 1.5, 2.0 silver-doped MBGs at a concentration of 400 μg/mL;
Referring to Figure 10, discloses a flowchart depicting steps of a method (1000) for preparation of mesoporous bioactive glass nanoparticles (MBGs), in accordance with an illustrated embodiment of a present disclosure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
Many modifications will be apparent to those skilled in the art without departing from the scope of the present invention as hereinbefore described with reference to the accompanying drawings.
Throughout this specification and the claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.
As used herein, the singular forms “a”, “an”, “the” include plural referents unless the context clearly dictates otherwise. Further, the terms “like”, “as such”, “for example”, “including” are meant to introduce examples which further clarify more general subject matter, and should be contemplated for the persons skilled in the art to understand the subject matter.
The present disclosure provides mesoporous bioactive glass (MBG) nanoparticles in which phosphorus pentoxide (P₂O₅) is partially substituted with silver oxide (Ag₂O). The composition includes silica (SiO₂) in the range of 55–65 wt%, calcium oxide (CaO) in the range of 30–40 wt%, and a combined amount of P₂O₅ and Ag₂O in the range of 2–10 wt%, with silver substitution in the range of 0.5–5 wt%. Unlike conventional MBGs where phosphorus is fixed and dopants are added, the disclosed approach introduces silver by substituting phosphorus, thereby acting as a network modifier. This substitution prevents collapse of the mesoporous architecture, generates non-bridging oxygens that yield surface silanol groups, and stabilizes the pore structure through local free volume. The resulting nanoparticles possess multifunctional features including antibacterial properties, ion release, and surface characteristics conducive to bioactivity.
When silver oxide is introduced in place of a portion of phosphorus pentoxide in a silica-calcia glass precursor, the silver cation (Ag⁺) behaves principally as a network modifier rather than as a network former. Phosphorus (as P⁵⁺ in P₂O₅) participates in creating bridging environments in the glass network; replacing part of those phosphorus sites with Ag⁺ alters the local bonding environment. Two complementary structural consequences are important:
A) Formation of non-bridging oxygens (NBOs) and surface silanol groups.: Substitution of a network former (P) by a monovalent network modifier (Ag⁺) increases the number of oxygen atoms that are not shared between two tetrahedra (NBOs). Many of these NBOs appear at or near the surface and hydrolyse to form –Si–OH (silanol) groups. These surface silanols are key active sites for subsequent interactions with body-like fluids and for nucleating Ca–P phases.
B) Prevention of pore collapse during gelation/aging: Because Ag⁺ does not strongly cross-link silica chains (unlike some multivalent dopants that promote additional Si–O–M bridges and cause network tightening), the silicate framework remains relatively open during hydrolysis/condensation and subsequent solvent evaporation. The larger ionic size and monovalent nature of Ag⁺ create local free volume within the pore walls rather than promoting tighter packing; this local free volume helps to stabilise the mesopore walls through the drying and template-removal steps and prevents pore shrinkage/collapse that would otherwise reduce surface area.
Hence, Ag substitution may preserve or even enhance mesoporosity and surface reactivity compared with compositions where stronger cross-linking dopants are added on top of a fixed P level.
The preserved mesoporous architecture plus elevated surface silanol density produce two direct consequences relevant to in-vitro bioactivity:
a) Increased local nucleation sites: Surface –Si–OH groups act as favourable anchoring/nucleation sites for adsorption of Ca²⁺ from SBF and for subsequent phosphate accumulation; this lowers the energetic barrier for hydroxy-carbonate apatite (HCA) nucleation. Thus, a composition with abundant surface silanols will show more rapid and extensive Ca–P precipitation on exposure to SBF.
b) Enhanced ion exchange and controlled dissolution: An open mesoporous network with high accessible surface area increases the rate at which network ions (Si, Ca) and dopant ions (Ag⁺) maybe released to the surrounding medium. Faster but controlled release of Ca²⁺ and Si (OH)₄ species increases local supersaturation with respect to Ca–P phases, accelerating HCA formation. At the same time, the mesopore geometry provides diffusion pathways that moderate release kinetics so the structure does not degrade catastrophically.
Such mechanistic features match the experimental observations (e.g., progressive HCA formation with SBF soaking, Ca/P ratios consistent with apatite phases as provided hereinbelow), and hence Ag substitution promoted HCA precipitation.
Silver’s well-known antimicrobial action results from Ag⁺ ion release and multiple interactions with microbes (membrane disruption, thiol binding to enzymes/proteins, interference with respiration and DNA). Ag⁺ is provided from within a preserved mesoporous matrix rather than as large surface aggregates:
Sustained Ag⁺ delivery from pores: Because the mesopore network is retained, Ag⁺ may diffuse steadily from internal sites into the medium; this gives a sustained antibacterial ion concentration at the particle/implant surface while avoiding burst release that might destabilise the glass.
No pore collapse from Ag incorporation: Unlike some divalent or trivalent dopants that cause cross-linking and pore shrinkage (reducing SSA and blocking ion pathways), Ag⁺’s modifier behaviour preserves pore channels — so antibacterial functionality is achieved without sacrificing the textural features critical to bioactivity and drug loading.
Thus, the material achieves broad-spectrum antibacterial performance together with preserved porosity and surface chemistry.
The mesoporous architecture along with surface silanols and controlled ionic dissolution combine to create a surface environment favourable for protein adsorption, cell adhesion and downstream cell responses:
Protein adsorption and cell adhesion: High surface area and silanol sites promote adsorption of serum proteins (fibronectin, vitronectin, etc.) that mediate cell attachment. Adsorbed protein conformation and density on a mesoporous surface favour integrin engagement and focal adhesion formation, supporting cell spreading and survival.
Ionic signalling for osteogenesis and angiogenesis: Released Si and Ca species are known to act as cues for osteoblastic activity (promoting proliferation and differentiation pathways) and may also modulate angiogenic signalling indirectly. The mesoporous scaffold provides sustained exposure to these ionic cues rather than a transient spike, which is beneficial for tissue-relevant cell responses.
Balanced antibacterial vs. cell compatibility: Because Ag⁺ release is moderated by the mesoporous network, antibacterial concentrations near the material may be achieved without producing cytotoxic levels in the local environment - consistent with the cytocompatibility and haemolysis results presented.
Finally, the acid treatment plus ethanol extraction template removal strategy plays a critical supporting role: it cleans the mesopore channels without the high-temperature condensation that converts silanol groups to Si–O–Si bridges. In contrast, calcination tends to reduce surface –Si–OH density and may sinter/contract pore walls. By removing the surfactant chemically at low temperature, the process retains the silanol population and the open mesopore walls created during EISA, thereby preserving the structural and surface features that the Ag substitution makes possible.
In a nutshell, (i) Ag⁺ acting as a network modifier, (ii) generation of non-bridging oxygen leading to surface silanols, (iii) creation of local free volume that stabilises pore walls, and (iv) low-temperature template removal give a material that simultaneously preserves mesoporous architecture and surface reactivity, provides controlled Ag⁺ release for antibacterial action, supports ion exchange and HCA nucleation, and presents surface features conducive to favourable cell responses. Hence, partial substitution of P₂O₅ by Ag₂O achieves the multifunctional performance due to such mechanistic links as demonstrated by experimental results provided herein below.
As shown in Figure 10, the nanoparticles are prepared via an acid-assisted sol–gel process (1000) integrated with evaporation-induced self-assembly (EISA). A surfactant such as Pluronic P123 is dissolved in ethanol and water, followed by sequential addition of tetraethyl orthosilicate (TEOS), calcium acetate, triethyl phosphate (TEP), and silver acetate precursors. Hydrolysis and condensation are induced under acidic conditions, and the sol is aged under controlled evaporation to generate ordered mesostructure. After drying, the surfactant template is removed using a two-step method: (i) acid treatment with sulfuric acid at 65°C, and (ii) ethanol extraction under reflux. Such an approach avoids high-temperature calcination and preserves surface silanol groups critical for bioactivity.
Experimental results
Mesoporous ternary SiO2-P2O5-CaO composition with theoretical ratios and their respective precursors (in grams) has been taken into consideration to synthesize the requisite materials, whose details are shown in Table 1. As synthesized MBG nanoparticles have been abbreviated with syntax “XAg-(6-X)P-58SMBG”, where X = 0.0, 0.5, 1.0, 1.5, and 2.0 mol %. The required glass materials are synthesized via acid assisted wet-chemistry based sol-gel approach by means of EISA. Furthermore, the SCA has been included in traditional sol-gel route to induce mesopore architecture of final product.
Table 1: 58S MBG composition in increasing Ag in spite of P2O5 along with their respective weights of the precursors for one gram batch.
MBG samples
(Abbreviations) Theoretical Chemical Compositions (Mole %) Precursors in their respective Compositions (in grams)
SiO2 CaO P2O5 Ag2O TEOS CaAc TEP AgAc
0.0Ag6.0P58SMBG 58 36 6 0 1.905 0.8978 0.3439 0
0.5Ag5.5P58SMBG 58 36 5.5 0.5 1.905 0.8978 0.3159 0.0131
1.0Ag5.0P58SMBG 58 36 5.0 1.0 1.905 0.8978 0.2878 0.0263
1.5Ag4.5P58SMBG 58 36 4.5 1.5 1.905 0.8978 0.2594 0.0396
2.0Ag4.0P58SMBG 58 36 4.0 2.0 1.905 0.8978 0.2311 0.0529
The requisite MBG materials have been synthesized by considering the initial precursors (tetraethyl orthosilicate) TEOS, Triethyl phosphate (TEP), calcium acetate hydrate (CaAc), and silver acetate (AgAc), which led through various stages during syneresis. Typically, sol-gel route engages into the formation of initial “sol” which get converted into “gel” after hydrolysis followed by condensation. Thus, the initial sol has been formed by taking 1g of P123 to dissolve into 15 g of ethanol (EtoH). After complete dissolution, all precursors are included into already prepared P123-EtoH-H2O mixture in a particular order in every “1 hour” interval by maintaining the constant molar ratio of 1:4 for both TEOS:EtoH; TEOS:H2O and weight ratio of 1:6 for Acetic acid:H2O. The overall admixture sol was kept for continuous stirring at 500 rpm at room temperature (298 K) to step a homogeneous “gel”. The subsequent wet gel is then reassigned to Borosil glassware based polystyrene petri dish in order to undergo EISA process, which were then positioned into an oven at a temperature of 313 K for 3 days for aging. The as aged sample is then dried at 333 K for next 24 hours in order to extract redundant EtoH and associated by-products. Subsequently, thermal effects admit the sample to crack down into powder form, thereby a firm interlocked pore architecture is attained. Furthermore, silver incorporated MBG samples are synthesized with similar routes with the addition of Ag precursors like AgAc in spite of TEP in composition. For template exclusion, there is second-hand “two step methodology” in order to extract the as used template Pluronic (P123) to obtain the final MBG sample. Here, the poly (propylene oxide) i.e. PO chain in P123 network structure crumbles and gets oxidized by using H2SO4. In first step, as synthesized 30 mg MBG powdered sample is immersed in 1 ml of 48 wt % H2SO4 at 65°C for 3 hours. Sample is then carefully supervised thereafter and allowing the sample to remain in amorphous phase. The treated MBG sample is thoroughly washed with distilled H2O multiple times and checked with pH meter to get the bases liquid with pH lying around 7 thereby the eluent becomes neutral. The second step of two step methodology lies where, EtoH extraction for utter expulsion of P123 from subsequent final product is used. The low temperature treatment of EtoH extraction has an upper hand than other traditional high temperature calcination method and are exhibited with high -Si-OH groups, high SSA, narrow pore size distribution. In this stage, overnight reflowing stirring of EtoH mediated wash away of acidic processed MBG powdered sample have been taken into consideration. It was then followed with two rounds of ultrasonication of samples and processed for 4-times centrifugation for half an hour at 4000 rpm.
The Textual characteristics of pristine MBG with increasing Ag (mol%) and morphological studies (including FESEM and HRTEM study) are shown in Table 2 and Figures 1A-1J. Even though there is a decrease in surface area with increasing silver content, there is also not that much considerable reduction in surface area.
Table 2: Textual characteristics of pristine MBG with increasing Ag (mol %)
Sample Description Surface
Area
(m2/g) Pore
Diameter
(nm) Pore volume
(cc/g)
0.0Ag6.0P58SMBG 641.7 3.7 0.07
0.5Ag5.5P58SMBG 726.7 3.9 0.27
1.0Ag5.0P58SMBG 822.2 3.9 0.25
1.5Ag4.5P58SMBG 746.4 3.9 0.31
2.0Ag4.0P58SMBG 715.9 3.9 0.35
Thus, as synthesized MBG samples with increasing silver as dopant remains with high surface area up to a good extent. The pore volume continuous increasing gradually with increasing silver contents. It is notable that the pore diameter shown in Table 2 and through isotherm plots in Figure 2A remains almost constant with increasing silver content.
The synthesis of Ag-based ternary MBG with composition 58 SiO2- 36 CaO- 6 P2O5 (mol %) was successfully demonstrated, where silver is varied in spite of P in composition. Here, Ag-MBG is synthesized by using modified sol-gel route with acid-assisted methodology by using evaporation induced self-assembly with supramolecular chemistry approach. As synthesized materials are exhibited with typical mesoporous nature and warm-hole type pore architecture shown in Figures 1A-1J. The synthesized MBG materials are exhibited with superior textural characteristics like high SSA shown in Table 2, and mono-modal type distribution shown in Figure 2B with increasing Ag content. Here, the structural and local atomic architectural studies as shown in Figures 3A and 3B, have been performed after SBF soaking for 7 days for all synthesized MBG samples. It is depicted from Figure 3A that the formed HCA retains its amorphous phase for initial 0.0 and 0.5 mol % Ag doped 58S-MBG sample, which showed a transition from amorphous to crystalline phase with increasing Ag concentration of 2 mol %. The increasing mol % of Ag i.e. 1% and 1.5% in compositions, thereby illustrates an indication of a minor crystalline phase, which leads to its fully grown CaP-based HCA phase (JCPDS-00-019-0272) for 2 mol % Ag contents. Furthermore, the precipitated HCA has been justified by the Figure 3B where the corresponding vibrational modes has been observed. Here, the 465 cm-1 band with bending motion of Si-O-Si group associated with bridging oxygen (OBG) is found to decrease with increasing immersion time especially with longer day i.e. 7 days and higher Ag contents like 2.0 mol %. Thus, decreasing symmetric stretching bending motion of Si-O-Si group pave the way to emergence of CaP clusters in matrices, which seems to be a quite good consistency with the results (shown in Figures 3A and 3B) outcomes as shown in previous section. The phosphate band at 560 cm-1 emerges much swiftly after 1 mol % of Ag. Hence, there may be realise the reduction in NBO at 968 cm-1, which ultimately give rise to carbonate band at 893 cm-1 as described in previous paragraph. Furthermore, robust advent of carbonate doublet bands at 1450 cm-1 and 1545 cm-1 for higher Ag content like 1.5 and 2.0 mol %, give rise to reduction in hydroxyl group at around 1630 cm-1. It has been justified that the HCA precipitated much promptly for higher Ag content in 58S MBG composition. Thus, Ag play a vital role in silicate network distortion which thereby pave the way for HCA growth.
The SBF after soaking for various interactions like 1, 4 and 7 days are collected, and its pH values has been noted as shown in Figure 4A to illustrate the ion-exchange kinetics interaction response. It has been revealed that the pH value attains a level of supersaturation after prolonged soaking of 7 days, which thereby leads to HCA precipitation. The crystallize CaP nanoparticles grown onto MBG exterior as shown in Figures 4B-4E. Here, the 2 mol % Ag-based 58S-MBG sample is completely covered or nucleated with crystalline Ca-P clusters with Ca/P ratio of 1.63, thereby showing a good consistency with results reported earlier.
Apart from the preliminary characterization of the as synthesized material, additionally the elemental analysis on pristine MBG with 2% Ag dopants for 7 days of immersion time have been carried out by EDAX study as shown in Figure 5. Here, the elemental distribution of various elements after soaking in SBF has been recorded. Superior textural properties are thereby obtained with high silanol (-Si-OH) content, which further helps in HCA precipitation, drug delivery, therapeutic ion release, and anti-bacterial study shown in Figures 4A-4E, 5, 6A-6C, and 7A-7B. In-vitro bioactivity study has been performed onto synthesised MBG samples and found that HCA precipitation strongly depend upon dopant concentration. Furthermore, anti-bacterial study with different stains like S. aureus, and E. coli has been study, where a significant high zone of inhibition nearly 2.5 cm (25 mm) with only 1.5-2 mol % of Ag is obtained, as demonstrated in Figures 6A-6C. Also, attachment viability of SaOS2 and H9C2 cells on different silver-doped MBGs shown in Figures 8A-8H. The results demonstrated that Ag-MBG nanoparticles effectively enhanced the adhesion of osteoblast-like SaOS2 cells and H9C2 cells, indicating favourable interactions with bone-forming cells and underscoring their suitability for bone tissue engineering. As shown in Figures 9A-9E that the different Silver-doped MBGs had almost no haemolysis at all the tested concentrations. The result indicated that Silver-doped MBGs were biocompatible.
Materials and Methods:
As synthesized MBG samples is then investigated on various front like structural, textural, and morphological using different characterization, whose details are as follows: Structural studies have been carried out by using Bruker, D8 discover X-ray diffractometer based high resolution powdered X-ray diffraction (HRXRD). Here, Cu-Kα radiation having λ = 1.5408 Å is used to salvage the structural knowledge for pristine and in-vitro bioactivity based soaked MBG materials. Furthermore, an accelerating voltage of 40 kV and current 40 mA with 2θ = 10° - 70° having step-size = 0.02°, step speed =1°/min is used while performing and retrieving the spectra.
Textural and porosity study has been checked on pristine MBGs by Nitrogen adsorption-desorption technique at 77 K with N2 as an adsorptive gas with Gemini VII 2390t Model from Micro-meritics instrument corporation. The samples have been degassed under continuous N2 flow at a temperature of 105°C for 1 day. SSA, and isotherm plots of degassed materials is extracted by Brunauer-Emmett-Teller, termed as BET and Barret-Joyner-Halenda called as BJH method respectively. Thus, porosity like Vp, average pore size and pore size distribution may easily be extracted by BJH methodology.
Ion exchange kinetics interaction study has been done by suitably measuring the pH value of soaked MBG samples for different interaction time of 1, 4 and 7 days. The study has been performed by using EUTECH instruments pH 700 from thermos scientific instrumentation. The morphological studies are carried out with electron microscopy, where field emission scanning electron microscope (FESEM) of Tescan model LYRA3 XMU is used to record micrographs. The micrograph of gold coated MBG samples before and after SBF soaking are captured to evade charging upshot at an accelerating voltage = 20 kV and with resolving power of 1.2 nm. In continuation, bright field high resolution transmission electron microscopy (BF- HRTEM) with Talos Cryo TEM model has been done to find the interior morphology. Here, bright field mode study is carried out with an accelerating voltage of 200 kV on pristine and SBF soaked MBG samples to find the relative changes in morphology after various time scales.
Fourier Transform Infrared (FTIR) with Nicolet 380 FTIR is performed on pristine and soaked MBG powdered samples to investigate the presence and change in chemical bonding in molecules at different time scale. The transmission mode is considered to record the spectra with range 400 - 4000 cm-1 at a resolution = 1 cm-1. Furthermore, sample processed for FTIR are prepared by mixing the sample with potassium-bromide KBr (Sigma Aldrich) in weight ratio of sample: KBr is 1:100 and final sample was ready by making pallets of it.
To perform the Kirby Bauer test onto as-synthesized MBG samples, filter paper discs of ampicillin were prepared by punching holes about 6 mm in diameter into Whatman filter paper. The discs were then sterilized by autoclaving at 15 lbs pressure for 30 min. Next, antibiotic stock solutions (40 mg/mL) were prepared by dissolving a measured amount of antibiotic powder in sterile distilled water. At the time of disc preparation, the stock solution was diluted to create the working solution (0.5 mg/mL). To obtain antibiotic disc of 10 µg, 20 μL of diluted solution poured onto the disc and let it dry in the laminar hood.
Mueller-Hinton agar (MHA) (HiMedia, India) was chosen as the standard growth medium, which was prepared according to the instructions of the manufacturer. Agar was poured into sterile Petri dishes to a 4 mm uniform depth and allowed to solidify at room temperature. Plates were kept at 4°C until use. Bacterial inoculum was prepared by suspending freshly cultured colonies, from 24 h old agar plates, into sterile saline (0.9% NaCl). The turbidity of the suspension was adjusted to 0.5 McFarland standard, which is about 1×108 CFU/mL. Then a sterile swab dipped into the inoculum tube and inoculate the dried surface of a MH agar plate by streaking the swab three times over the entire agar surface by rotating to ensure an even distribution of the inoculum. Leaving the lid slightly ajar, allow the plate to sit at room temperature at least 3 to 5 min. Using forceps, carefully placed the antimicrobial-impregnated disks onto the surface of the agar, one at a time. Gently pressed each disk with the forceps to ensure full contact with the agar. Once all the disks are positioned, replaced the lid, inverted the plates, and incubate them at 37°C for 16 to 18 h for E. coli and 24 h for S. aureus in an air incubator.
Bacterial cultures were grown in the Mueller-Hinton broth (MHB) to the desired optical density (A600 nm), ensuring cultures were in the logarithmic growth phase. Stock solutions of test compounds (0.5, 1.0, 1.5, 2.0 mole % Silver doped MBGs were prepared, followed by dilution in the test medium to 2 times the highest desired concentration. Using a multipipettor, 100 µL of medium was dispensed into wells of a 96-well microtiter plate, and 100 µL of the antibiotic stock was added to the wells in column 1. Serial twofold dilutions were performed across columns 1–10, with column 11 serving as the bacterial growth control and column 12 as the sterility control. After preparing a standardized bacterial inoculum (10⁴–10⁵ CFU/mL), 5 µL of the inoculum was added to each test well, except for the sterility control. Plates were incubated at 37°C for 18–36 h, and bacterial purity was verified via streaking on agar plates. Growth inhibition was assessed by measuring absorbance using an ELISA plate reader, with column 12 serving as the blank. The MIC was defined as the lowest drug concentration that reduced bacterial growth by ≥50% or ≥90% for MIC50 and MIC90, respectively, relative to the untreated control.
SaOS-2 human osteosarcoma cells acquired from NCCS, Pune was maintained in McCoy's 5A media (30-2007 ™) supplemented with 10% FBS and H9C2 rat cardiomyoblast exhibiting skeleton muscles properties also acquired from NCCS, Pune was maintained in DMEM(AL0678) high glucose supplemented with 10% FBS kept maintained in standard tissue culture incubator at 37 °C with 5% CO2. SaOS-2 cells were plated in each well of a 96-well plate and were allowed to adhere and spread for 24 h. The test compounds were added at different concentration, and the cells were cultured for different time duration at 37 °C. MTT solution (at final concentration of 0.3 mg/mL) was added to each well, and the cultures were incubated for an additional 3 h. The absorbance at 540 nm was determined in each well with a 96-well plate reader. The growth of the treated cells was compared with that of untreated cells for calculating the percent viability.
Blood compatibility was assessed using a hemolysis assay. Fresh chicken blood was collected in EDTA-vacutainer. 2 mL sample of whole blood was mixed with 4 mL of phosphate-buffered saline (PBS) and centrifuged at 10,000 g for 5 min to isolate red blood cells (RBCs). The RBCs were subsequently washed five times with 10 mL of PBS and diluted to a final volume of 20 mL in PBS. Here, 0.2 mL aliquot of the diluted RBC suspension was mixed with 0.8 mL of test compounds suspension prepared in PBS at concentrations of 2.5, 12.5, 62.5, 125, 250, or 500 μg/mL. This resulted in final concentrations of 2, 10, 50, 100, 200, or 400 μg/mL for the test group. Distilled water and PBS were used as positive and negative controls, respectively. Each group was tested in triplicates. Following incubation at room temperature for 4 h, the samples were centrifuged at 10,000 g for 5 min. Then, 100 μL of the supernatant from each sample was transferred to a 96-well plate. Absorbance was measured at 577 nm using a microplate reader (TECAN Infinite M200, Austria), with 655 nm as the reference wavelength. The degree of hemolysis was calculated using the standard formula.
The mesoporous bioactive glass (MBG) nanoparticles of the present disclosure are suitable for incorporation into a variety of biomedical devices owing to their unique combination of structural and functional properties. Their mesoporous architecture provides high surface area and accessible pore channels, their surface silanol groups act as nucleation sites for hydroxy-carbonate apatite formation, and their controlled release of silver ions imparts antibacterial activity without collapse of the pore structure. These features collectively enable simultaneous antibacterial defense, enhanced bioactivity, and compatibility with bone and vascular tissues.
In one embodiment, the MBG nanoparticles are incorporated into three-dimensional scaffolds designed for bone regeneration. The nanoparticles may be dispersed within polymeric or hydrogel matrices to produce porous structures with interconnected networks. Within such scaffolds, the MBG nanoparticles contribute to early-stage bonding with host tissue by providing silanol groups that nucleate apatite layers. The mesopores also serve as reservoirs for growth factors or therapeutic molecules, enabling sustained release. Furthermore, ionic dissolution products such as Si, Ca, and Ag support osteogenic differentiation and angiogenic signalling, while antibacterial activity reduces the risk of infection during implantation.
In another embodiment, the MBG nanoparticles are incorporated into injectable or moldable bone filler formulations. The mesoporosity and surface chemistry of the nanoparticles facilitate rapid interfacial bonding between the filler and host bone. When dispersed within carriers such as collagen, gelatin, or calcium phosphate cements, the nanoparticles enhance the biological activity of the filler and reduce infection risk. Their ability to release therapeutic ions ensures that the filler material not only fills defects but also actively promotes bone regeneration.
The MBG nanoparticles may also be embedded in biodegradable polymers such as poly(lactic acid), polycaprolactone, or polyethylene glycol to form polymer–ceramic composites. In such composites, the MBG particles act as bioactive fillers that overcome the bioinert nature of polymers. The mesoporous texture enables strong interfacial bonding with polymer chains, which improves the mechanical integrity of the composite. At the same time, the nanoparticle-mediated ion release imparts long-term bioactivity and antibacterial action to the composite scaffold.
In yet another embodiment, the MBG nanoparticles are deposited as part of a coating layer on metallic implants such as titanium-based orthopaedic or dental implants. The nanoparticles provide high surface reactivity through silanol groups, which rapidly induce apatite formation on the implant surface, thereby improving osseointegration. Simultaneously, the controlled release of silver ions prevents bacterial colonization at the implant interface, addressing one of the major causes of implant failure. The mesoporous nature of the coating also allows optional loading of antibiotics or growth factors to further tailor the biological response.
Across all device embodiments, the mesoporous architecture of the MBG nanoparticles ensures controlled ion release. Calcium and silicon species are released gradually, maintaining a local environment conducive to bioactivity and tissue integration. Silver ions are released in concentrations sufficient to provide antibacterial protection without reaching cytotoxic levels. This balanced release profile is inherent to the nanoparticle architecture and ensures multifunctionality in device applications.
Through incorporation into scaffolds, bone fillers, polymer–ceramic composites, and implant coatings, the mesoporous bioactive glass nanoparticles of the present disclosure provide devices with combined antibacterial functionality, enhanced bioactivity, and favourable material–tissue interactions. These embodiments directly illustrate the versatility and broad applicability of the nanoparticles in biomedical device design.
The foregoing descriptions of exemplary embodiments of the present disclosure have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to best explain the principles of the disclosure and its practical application, to thereby enable others skilled in the art to best utilize the disclosure and various embodiments with various modifications as are suited to the particular use contemplated.

, Claims:We Claim
1. A mesoporous bioactive glass nanoparticle comprising:
silica (SiO₂) in the range of 55–65 wt%,
calcium oxide (CaO) in the range of 30–40 wt%, and
a combined amount of phosphorus pentoxide (P₂O₅) and silver oxide (Ag₂O) in the range of 2–10 wt%,
wherein phosphorus pentoxide is partially substituted with silver oxide in the range of 0.5–5 wt% relative to the total glass composition, the substitution maintaining mesoporous architecture by acting as a network modifier that prevents densification of the silicate framework, introducing non-bridging oxygens that form surface silanol groups, and creating local free volume that stabilizes the pore structure, thereby enabling hydroxy-carbonate apatite nucleation, ion exchange, drug loading, and antibacterial functionality while preserving structural characteristics that support osteogenic and angiogenic responses.
2. The mesoporous bioactive glass nanoparticle as claimed in claim 1, wherein the nanoparticles have a pore volume in the range of 0.2–0.5 cc/g.
3. The mesoporous bioactive glass nanoparticle as claimed in claim 1, wherein the silver substitution provides release of Ag⁺ ions in physiological environments, thereby conferring antibacterial functionality against microorganisms.
4. The mesoporous bioactive glass nanoparticle as claimed in claim 1, wherein the presence of surface silanol groups derived from phosphorus substitution promotes nucleation of hydroxy-carbonate apatite when exposed to simulated body fluid.
5. The mesoporous bioactive glass nanoparticle as claimed in claim 1, wherein the stabilized mesoporous architecture with non-bridging oxygens provides surface characteristics conducive to cellular adhesion and proliferation relevant to osteogenic and angiogenic responses.
6. A process (1000) for preparing mesoporous bioactive glass nanoparticles, the process (1000) comprising:
dissolving a surfactant in ethanol and water,
sequentially adding tetraethyl orthosilicate (TEOS), calcium acetate, triethyl phosphate, and silver acetate in amounts sufficient to obtain a composition comprising silica (SiO₂) in the range of 55–65 wt%, calcium oxide (CaO) in the range of 30–40 wt%, and a combined amount of phosphorus pentoxide (P₂O₅) and silver oxide (Ag₂O) in the range of 2–10 wt%, wherein phosphorus pentoxide is partially substituted with silver oxide in the range of 0.5–5 wt% relative to the total glass composition,
inducing hydrolysis and condensation under acid-assisted sol–gel conditions,
subjecting the resulting sol to evaporation-induced self-assembly and aging,
drying to obtain a gel, and
removing the surfactant using a two-step method comprising acid treatment followed by ethanol extraction,
wherein the substitution of phosphorus pentoxide with silver oxide maintains the mesoporous architecture by acting as a network modifier, generating non-bridging oxygens that form surface silanol groups and free volume within the pore walls, thereby yielding nanoparticles with preserved mesoporous structure and inherent antibacterial functionality.
7. The process (1000) as claimed in claim 6, wherein the surfactant is Pluronic P123.
8. The process (1000) as claimed in claim 6, wherein the acid treatment for template removal is performed using sulfuric acid at a temperature of about 65°C.
9. The process (1000) as claimed in claim 6, wherein the ethanol extraction step is carried out under reflux with stirring for at least 12 hours.
10. A biomedical device comprising mesoporous bioactive glass nanoparticles, the nanoparticles providing structural features including mesoporosity, surface silanol groups, and silver ion release, thereby imparting antibacterial functionality and surface characteristics conducive to bioactivity and cell compatibility.
11. The biomedical device as claimed in claim 10, wherein the device is a porous scaffold comprising a polymer–ceramic composite incorporating the mesoporous bioactive glass nanoparticles.
12. The biomedical device as claimed in claim 10, wherein the device is a bone filler composition including the mesoporous bioactive glass nanoparticles dispersed within a biocompatible matrix.
13. The biomedical device as claimed in claim 10, wherein the device is a coating on an orthopedic or dental implant, the coating comprising the mesoporous bioactive glass nanoparticles to enhance surface bioactivity.
14. The biomedical device as claimed in claim 10, wherein the mesoporous bioactive glass nanoparticles within the device provide controlled ion release characteristics that contribute to bioactivity and integration with surrounding material surfaces.