Silica xerogel carrier material for controlled release of toremifene citrate

E-jet printed polycaprolactone with strontium-substituted mesoporous bioactive glass nanoparticles for bone tissue engineering

Osteoporosis, characterized by reduced bone mineral density and increased fracture risk, poses a significant health challenge, particularly for aging populations. Systemic treatments often lead to adverse side effects, emphasizing the need for localized solutions. This study introduces a 3D-printed polycaprolactone (PCL) scaffold embedded with strontium-substituted mesoporous bioactive glass nanoparticles (Sr-MBGNPs) and icariin (ICN) for the targeted regeneration of osteoporotic bone. The scaffold was characterized using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), ion release studies, and cellular assays, which confirmed its dual functionality in both enhancing osteoblast proliferation and differentiation and inhibiting osteoclastogenesis. The optimized Sr-MBGNP concentration ensured sustained ion release, superior hydrophilicity, and bioactivity without compromising scaffold integrity. Additionally, e-jet printing provided high precision and uniform pore sizes conducive to cellular activity. This novel scaffold platform demonstrates a promising localized treatment strategy, reducing systemic side effects while improving fixation stability. The innovative integration of Sr-MBGNPs and ICN highlights its potential to revolutionize osteoporosis therapy by promoting bone regeneration and mitigating bone resorption.

Iodine Capture with Mechanically Robust Heat-Treated Ag-Al-Si-O Xerogel Sorbents

Various radionuclides are released as gases during reprocessing of used nuclear fuel or during nuclear accidents including iodine-129 (129I) and iodine-131 (131I). These isotopes are of particular concern to the environment and human health as they are environmentally mobile and can cause thyroid cancer. In this work, silver-loaded heat-treated aluminosilicate xerogels (Ag-HTX) were evaluated as sorbents for iodine [I2(g)] capture. After synthesis of the base NaAlSiO4 xerogel, a heat-treatment step was performed to help increase the mechanical integrity of the NaAlSiO4 gels (Na-HTX) prior to Ag-exchanging to create Ag-HTX xerogels. Samples were characterized by powder X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, Brunauer-Emmett-Teller analysis, gravimetric iodine loading, nanoindentation, and dynamic mechanical analysis. The structural and chemical analyses of Ag-HTX showed uniform distribution of Ag throughout the gel network after Ag-exchange. After I2(g) capture, the AgI crystallites were observed in the sorbent, verifying chemisorption as the primary iodine capture mechanism. Iodine loading of this xerogel was 0.43 g g-1 at 150 °C over 1 day and 0.52 g g-1 at 22 °C over 33 days. The specific surface area of Ag-HTX was 202 m2 g-1 and decreased to 87 m2 g-1 after iodine loading. The hardness of the Na-HTX was >145 times higher than that of the heat-treated aerogel of the same starting composition. The heat-treatment process increased Young's modulus (compressive) value to 40.8 MPa from 7.0 MPa of as-made xerogel, demonstrating the need for this added step in the sample preparation process. These results show that Ag-HTX is a promising sorbent for I2(g) capture with good iodine loading capacity and mechanical stability.

Copper complex with sulfamethazine and 2,2'-bipyridine supported on mesoporous silica microspheres improves its antitumor action toward human osteosarcoma cells: cyto- and genotoxic effects

Ideal drugs to cure cancer leave normal cells unharmed while selectively turning tumor cells unviable. Several copper complexes have been able to selectively slow down tumor proliferation. We hypothesized that Cu(smz)₂(bipy)·H₂O (1)-a copper-complex that has two ligands capable of interacting with DNA-would outperform Cu(smz)₂(OH₂)·2H₂O (2), and also that supporting 1 on mesoporous silica spheres would decrease even further tumor cell viability in vitro. After exposing osteosarcoma cells (MG-63) and normal phenotype cells of bone origin (MC3T3-E1) to either complex, we studied their toxic effect and mechanisms of action. We determined cell viability (MTT assay) and quantified formation of reactive oxygen species (oxidation of DHR-123 to rhodamine). Moreover, we assessed genotoxicity from (i) formation of micronucleus (MN assay) and (ii) damage of DNA (Comet assay). After the exposure of 1 supported on silica spheres, we tested cell viability. Our results confirm our hypotheses: inhibition of tumor cells follows: supported 1 > dissolved 1 > 2. Future work that enhances the load of the complex exclusively in mesopores may improve the ability of 1 to further inhibit tumor cell viability.

Xerogel modified diatomaceous earth microparticles for controlled drug release studies

An alternative facile approach for the surface modification of naturally available diatoms with xerogel for controlled drug release applications.

Hybrid catechin silica nanoparticle influence on Cu(II) toxicity and morphological lesions in primary neuronal cells

Morphological alterations compromising inter-neuronal connectivity may be directly linked to learning-memory deficits in Central Nervous System neurodegenerative processes. Cu(II)-mediated oxidative stress plays a pivotal role in regulating redox reactions generating reactive oxygen species (ROS) and reactive nitrogen species (RNS), known contributors to Alzheimer's disease (AD) pathology. The antioxidant properties of flavonoid catechin have been well-documented in neurodegenerative processes. However, the impact that catechin encapsulation in nanoparticles may have on neuronal survival and morphological lesions has been poorly demonstrated. To investigate potential effects of nano-encapsulated catechin on neuronal survival and morphological aberrations in primary rat hippocampal neurons, poly(ethyleneglycol) (PEG) and cetyltrimethylammonium bromide (CTAB)-modified silica nanoparticles were synthesized. Catechin was loaded on silica nanoparticles in a concentration-dependent fashion, and release studies were carried out. Further physicochemical characterization of the new nano-materials included elemental analysis, particle size, z-potential, FT-IR, Brunauer-Emmett-Teller (BET), thermogravimetric (TGA), and scanning electron microscopy (SEM) analysis in order to optimize material composition linked to the delivery of loaded catechin in the hippocampal cellular milieu. The findings reveal that, under Cu(II)-induced oxidative stress, the loading ability of the PEGylated/CTAB silica nanoparticles was concentration-dependent, based on their catechin release profile. The overall bio-activity profile of the new hybrid nanoparticles a) denoted their enhanced protective activity against oxidative stress and hippocampal cell survival compared to previously reported quercetin, b) revealed that morphological lesions affecting neuronal integrity can be counterbalanced at high copper concentrations, and c) warrants in-depth perusal of molecular events underlying neuronal function and degeneration, collectively linked to preventive nanotechnology in neurodegeneration.

Injectable silica-permanganate gel as a slow-release MnO4(-) source for groundwater remediation: rheological properties and release dynamics

Injectable slow-release permanganate gels (ISRPGs), formed by mixing aqueous KMnO4 solution with fumed silica powders, may have potential applications in remediating chlorinated solvent plumes in groundwater. A series of batch, column, and two-dimensional (2-D) flow cell experiments has been completed to characterize the ISRPG and study the release of permanganate (MnO4(-)) under a variety of conditions. The experiments have provided information on ISRPG rheology, MnO4(-) release dynamics and distribution in porous media, and trichloroethene (TCE) destruction by the ISRPG-released oxidant. The gel possesses shear thinning characteristics, resulting in a relatively low viscosity during mixing, and facilitating subsurface injection and distribution. Batch tests clearly showed that MnO4(-) diffused out from the ISRPG into water. During this process, the gel did not dissolve or disperse into water, but rather maintained its initial shape. Column experiments demonstrated that MnO4(-) release from the ISRPG lasted considerably longer than that from an aqueous solution. In addition, due to the longer release duration, TCE destruction by ISRPG-released MnO4(-) was considerably more effective than that when MnO4(-) was delivered using aqueous solution injection. In the 2-D flow cell experiments, it was demonstrated that ISRPGs released a long-lasting, low-concentration MnO4(-) plume potentially sufficient for sustainable remediation in aquifers.

Deferasirox loaded on fumed silica nanoparticles used in cancer treatment

Fumed silica nanoparticles loaded with deferasirox are three and five times more cytotoxic than cisplatin and deferasirox against MDA-MB-23, respectively.

The Design of Nanostructured Metronidazole-Loaded HPC/Oxide Xerogel Composites: Influence of the Formulation Parameters on In Vitro Characterisation

In this study, oxide and polymer/oxide xerogels with metronidazole were prepared and examined as carriers of drug for the local application to the bone. The nanoporous SiO2-CaO-P2O5 and HPC-SiO2-CaO-P2O5 xerogel materials with different amounts of the polymer [hydroxypropyl cellulose (HPC)] were prepared using the sol-gel technology, and their physicochemical properties were characterised with respect to chemical structure [by Fourier transform infrared spectroscopy (FTIR)], porosity and the specific surface area of solids (BET), crystallinity [by X-ray powder diffraction (XRD)], morphology [by scanning electron microscope (SEM)] and the in vitro release of the metronidazole over time (by UV-vis spectroscopy, in the ultraviolet light region). HPC-modified oxide xerogels as the carriers of drug showed slower release of metronidazole, due to the structure and stronger interactions with drug as compared with the pure oxide xerogel. Kinetic analysis indicated diffusional mechanism of drug release from all xerogel carriers. HPC addition to the oxide material resulted in a decrease in the porosity and improved the bioactive properties of xerogels. Obtained results for xerogel composites suggest that the metronidazole-loaded xerogels could be attractive candidates for local delivery systems particularly to a bone.

Silica-based matrices: State of the art and new perspectives for therapeutic drug delivery

Colloidal carriers based on silica (Si) matrices are an innovative approach within the context of therapeutic drug delivery systems. These carriers are emerging as a great promise for diagnosis and treatment of a wide range of injuries, particularly in cancer and infectious diseases. In addition, bioencapsulation for biosensing and cell therapy in silica sol-gel allows the survival of enzymes and cells for a long period of time. Owing to their porosity, large surface area, and high capability of functionalization, silica nanoparticles (SiNP) have been considered as an attractive option for several bioanalysis applications, such as selective bioseparation, imaging, and drug and gene delivery. However, although great advances are achieved in the biomedical fields, some toxicity effects can be associated with the use of SiNP. This article aims to present a comprehensive review of recent technological advances for silica matrices in biomedical applications, as well as the potential impact of silica-based materials on human health and environment.

Mass and surface fractal in supercritical dried silica aerogels prepared with additions of sodium dodecyl sulfate

Silica wet gels were prepared from hydrolysis of tetraethoxysilane (TEOS) with additions of sodium dodecyl sulfate (SDS). The surfactant was removed after gelation. Wet gels exhibited mass-fractal structure with mass-fractal dimension D (typically around 2.25) in a length scale extending from a characteristic size ξ (typically about 10 nm) of the mass-fractal domains to a characteristic size a0 (typically between 0.3 and 0.4 nm) of the primary particles building up the fractal domains. ξ increased while D and a0 diminished slightly as the SDS quantity increased. Aerogels with typical specific surface of 1000 m(2)/g and density of 0.20 g/cm(3) were obtained by supercritical drying of the wet gels after washing with ethanol and n-hexane. The pore volume and the mean pore size increased with the increase of the SDS quantity. The aerogels presented most of the mass-fractal characteristics of the original wet gels at large length scales and exhibited at a higher resolution level at about 0.7 nm a crossover to a mass-surface fractal structure, with apparent mass-fractal dimension Dm ∼ 2.4 and surface-fractal dimension Ds ∼ 2.6, as inferred from small-angle X-ray scattering (SAXS) and nitrogen adsorption data.

Novel anti-infective implant substrates: controlled release of antibiofilm compounds from mesoporous silica-containing macroporous titanium

Bone implants with open porosity enable fast osseointegration, but also present an increased risk of biofilm-associated infections. We design a novel implant material consisting of a mesoporous SiO2 diffusion barrier (pore diameter: 6.4 nm) with controlled drug release functionality integrated in a macroporous Ti load-bearing structure (fully interconnected open porosity: 30%; pore window size: 0.5-2.0 μm). Using an in vitro tool consisting of Ti/SiO2 disks in an insert set-up, through which molecules can diffuse from feed side to release side, a continuous release without initial burst effect of the antibiofilm compound toremifene is sustained for at least 9 days, while release concentrations (up to 17 μM daily) increase with feed concentrations (up to 4mM). Toremifene diffusivity through the SiO2 phase into H2O is estimated around 10(-13)m(2)/s, suggesting configurational diffusion through mesopores. Candida albicans biofilm growth on the toremifene-release side is significantly inhibited, establishing a proof-of-concept for the drug delivery functionality of mesoporous SiO2 incorporated into a high-strength macroporous Ti carrier. Next-generation implants made of this composite material and equipped with an internal reservoir (feed side) can yield long-term controlled release of antibiofilm compounds, effectively treating infections on the implant surface (release side) over a prolonged time.

The influence of sol–gel-derived silica coatings functionalized with betamethasone on adipose-derived stem cells (ASCs)

Silica-based sol–gel coatings have gained attention in bone therapies and orthopedic applications, due to the biocompatibility and bioactivity, including a high potential for the controlled release both in vitro and in vivo. Bioactive materials are created to facilitate the biocompatibility of orthopedic implants. One of the promising alternatives is biomaterials with immobilized drugs. In this study we demonstrated for the first time novel sol–gel-derived silica coatings with active amino groups (SiO2(NH2)) functionalized with a steroid drug—betamethasone, applied to a substrate 316 L using dip coating technique. The presence of betamethasone in functionalized coatings was directly confirmed by Raman spectroscopy and energy-dispersive X-ray spectroscopic analysis. The wettability was evaluated by the sessile drop method, while the surface free energy was estimated based on the contact angles measured. Our results showed a shift in surface properties from hydrophobic to hydrophilic after application of the coatings. We have investigated the morphology, proliferation factor, and the population doubling time of adipose-derived stem cells for biological purposes. Moreover, the analysis of the distribution and localization of cellular microvesicles was performed to evaluate the influence of functionalized surfaces on cellular cytophysiological activity. Increased proliferation and activation of cells, determined by the observations of microvesicles shedding processes, provided evidence of the availability of the drug. Therefore, we conclude that the sol–gel synthesis proposed here allows to improve the metal substrates and can be successfully used for immobilization of betamethasone. This in turn enables the direct delivery of the drug with implanted material into the wound site, and to stimulate the activity of cells to enhance tissue regeneration.

Structure of hydrophobic ambient-pressure-dried aerogels prepared by sonohydrolysis of tetraethoxysilane with additions of N,N-dimethylformamide

Silica wet gels with the same silica content were prepared by the sonohydrolysis of tetraethoxysilane (TEOS) with additions of dimethylformamide (DMF). DMF plays a role in the overall hydrolysis/gelification/aging step of the sol-gel process, providing more consolidated wet gels with larger syneresis degrees and densities. The structure of the as-obtained wet gels can be interpreted as being built up of mass-fractal domains with fractal dimension D = 2.2 and radius of gyration decreasing from about 14 to 12 nm with increasing quantity of DMF. Monolithic hydrophobic aerogels were prepared after washing of the wet gels with isopropyl alcohol (IPA), silylation with trimethylchrorosilane (TMCS), and ambient-pressure drying (APD). The specific surface area of the APD aerogels was found to be about 900 m(2)/g, and the mean silica particle size was about 2.0 nm, approximately independent of the DMF quantity, whereas the porosity decreased slightly with increasing amount of DMF, fairly accompanying the behavior of the radius of gyration of the precursor wet gels. The mass-fractal characteristics were preserved in the APD aerogels, but the radius of gyration of the mass-fractal domains was reduced to values between 2.8 to 4.0 nm, with the values decreasing slightly with the DMF quantity, and the fractal domains developed a surface-mass-fractal structure with the overall washing/silylation/APD treatment. The structural characteristics of the APD aerogels as determined by SAXS were found to be in notable agreement with those inferred from nitrogen adsorption.

Pore-forming compounds as signal transduction elements for highly sensitive biosensing

Pore-forming compounds are attracting much attention due to the signal transduction ability for the development of highly sensitive biosensing. In this review, we describe an overview of the recent advances made by our group in the design of molecular sensing interfaces of spherical and planar lipid bilayers and natural bilayers. The potential uses of pore-forming compounds, such as gramicidin and MCM-41, in lipid bilayers and natural glutamate receptor channels in biomembrane are presented.

Multi-arm PEG/silica hydrogel for sustained ocular drug delivery

In the present study, a series of sustained drug delivery multiarm poly(ethylene glycol) (PEG)/silica hydrogels were prepared and characterized. The hydrogels were formed by hydrolysis and condensation of poly(4-arm PEG silicate) using the sol-gel method. The relationships between water content in the PEG/silica hydrogel and stability as well as rheological properties were evaluated. Scanning electron microscopy analysis of the PEG/silica hydrogels revealed water content-dependent changes in microstructure. An increase in water content resulted in larger pores within the hydrogel, longer gelation time and higher viscosity. The PEG/silica hydrogels were loaded with dexamethasone (DMS) or dexamethasone sodium phosphate (DMSP), drugs that are hydrophobic and hydrophilic in nature, respectively. Evaluation of in vitro release revealed a zero-order release profile for DMS over the first 6 days, suggesting that degradation of the silica hydrogel matrix was the primary mechanism of drug release. It was also found that the drug-release profile could be tailored by varying the water content used during hydrogel preparation. In contrast, more than 90% of DMSP was released within 1 h, suggesting that DMSP release was only controlled by diffusion. Overall, results from this study indicate that PEG/silica hydrogels may be promising drug-eluting depot materials for the sustained delivery of hydrophobic, ophthalmic drugs.

Nanostructural control of the release of macromolecules from silica sol-gels

The therapeutic use of biological molecules such as growth factors and monoclonal antibodies is challenging in view of their limited half-life in vivo. This has elicited the interest in delivery materials that can protect these molecules until released over extended periods of time. Although previous studies have shown controlled release of biologically functional BMP-2 and TGF-β from silica sol-gels, more versatile release conditions are desirable. This study focuses on the relationship between room temperature processed silica sol-gel synthesis conditions and the nanopore size and size distribution of the sol-gels. Furthermore, the effect on release of large molecules with a size up to 70kDa is determined. Dextran, a hydrophilic polysaccharide, was selected as a large model molecule at molecular sizes of 10, 40 and 70kDa, as it enabled us to determine a size effect uniquely without possible confounding chemical effects arising from the various molecules used. Previously, acid catalysis was performed at a pH value of 1.8 below the isoelectric point of silica. Herein the silica synthesis was pursued using acid catalysis at either pH 1.8 or 3.05 first, followed by catalysis at higher values by adding base. This results in a mesoporous structure with an abundance of pores around 3.5nm. The data show that all molecular sizes can be released in a controlled manner. The data also reveal a unique in vivo approach to enable release of large biological molecules: the use more labile sol-gel structures by acid catalyzing above the pH value of the isoelectric point of silica; upon immersion in a physiological fluid the pores expand to reach an average size of 3.5nm, thereby facilitating molecular out-diffusion.

Synthesis and enhanced thermal stability of albumins@alumina: towards injectable sol-gel materials

A major obstacle to the introduction of bioactively-doped sol-gel based materials for medical applications has been the fact that silica - the most widely studied sol-gel material - despite being a GRAS material, which is widely used as an additive in foods and drug formulations, is still not approved by regulatory agencies for intramuscular injections. Here we point to a potential solution to this problem by shifting the weight to alumina, which is approved for injections as the most common immunization adjuvant. Towards the achievement of this goal we describe the development of protein entrapment methods tailored to alumina, and show high thermal stability of protein-dopants, using a newly developed DSC methodology for this purpose.

Influence of surfactants on the release behaviour and structural properties of sol-gel derived silica xerogels embedded with metronidazole

The aim of this study was to obtain stable and controlled release silica xerogels containing metronidazole (MT) prepared with surfactants with different charges: cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulphate (SDS) and hydroxypropyl cellulose (HPC), which could be the promising carrier materials used as the implantable drug delivery systems. The xerogels were prepared by the sol-gel method. The influence of various formulation precursors on porosity parameters and drug release were investigated. Addition of surfactants showed a promising result in controlling the MT release. Dissolution study revealed increased release of MT from silica modified SDS and CTAB, whereas the release of MT from silica modified HPC considerably decreased, in comparison with unmodified silica. The addition of surfactants showed slight changes in porosity parameters. All xerogels are characterized by a highly developed surface area (701-642 m(2) g(-1)) and mesoporous structure. The correlation between pore size obtained matrices and release rate of drug was also observed. Based on the presented results of this study, it may be stated that applied xerogel matrices: pure silica and surfactants-modified silica could be promising candidates for the formulation in local delivery systems.

Comparison of mesoporous silicon and non-ordered mesoporous silica materials as drug carriers for itraconazole

Mesoporous materials have an ability to enhance dissolution properties of poorly soluble drugs. In this study, different mesoporous silicon (thermally oxidized and thermally carbonized) and non-ordered mesoporous silica (Syloid AL-1 and 244) microparticles were compared as drug carriers for a hydrophobic drug, itraconazole (ITZ). Different surface chemistries pore volumes, surface areas, and particle sizes were selected to evaluate the structural effect of the particles on the drug loading degree and on the dissolution behavior of the drug at pH 1.2. The results showed that the loaded ITZ was apparently in amorphous form, and that the loading process did not change the chemical structure/morphology of the particles' surface. Incorporation of ITZ in both microparticles enhanced the solubility and dissolution rate of the drug, compared to the pure crystalline drug. Importantly, the physicochemical properties of the particles and the loading procedure were shown to have an effect on the drug loading efficiency and drug release kinetics. After storage under stressed conditions (3 months at 40 °C and 70% RH), the loaded silica gel particles showed practically similar dissolution profiles as before the storage. This was not the case with the loaded mesoporous silicon particles due to the almost complete chemical degradation of ITZ after storage.

Ordered mesoporous silicates as matrices for controlled release of drugs

Interest in and thereby also development of ordered mesoporous silicates as drug delivery devices have grown immensely over the past few years. On hand selected cases from the literature, the power of such systems as delivery devices has been established. Specifically, it is shown how it is possible to enhance the release kinetics of poorly soluble drugs by embedding them in mesoporous silicates. Further critical factors governing the structure and release of the model drug itraconazole incorporated in an SBA-15 matrix are briefly reviewed. The possibility of functionalizing the surface of mesoporous matrices also under harsher conditions offers a broad platform for the design of stimuli-responsive drug release, including pH responsive systems and systems which respond to the presence of specific ions, reducing agents, magnetic field or UV light, whose efficiency and biocompatibility has been established in vitro.

Effects of water on the structure and low/high temperature stability of confined proteins

In this study well-characterized model proteins were confined in silica nanoporous matrices. Confinement of the proteins in silica matrices allowed us to explore the role of water hydrogen bonding on the structures of the proteins in a broad range of temperatures (-120 degrees C to 95 degrees C). At low temperatures confinement suppressed freezing of water, which remained in the liquid state. We obtained direct evidence that the changes in the hydrogen bonding of water induced changes in the structure of confined proteins. At high temperatures, a reduction of hydrogen bonding of water facilitated protein-silica interactions and the confined proteins underwent denaturation. However, the incorporation of the osmolyte, trehalose, reduced protein-silica interactions, and altered the hydrogen bonding of water. As a result, the high temperature thermal stability of the confined proteins was greatly improved.

In-vitro controlled release of doxorubicin from silica xerogels

This study aimed at the development of a novel silica xerogel matrix as a delivery tool for an anti-cancer drug. Doxorubicin was incorporated as a hydrochloride salt during hydrolysis and polycondensation of tetraethylorthosilicate (TEOS) in the sol-gel process. The effect of sol-gel synthesis parameters (drug concentration, size of the device and lyophilizing process) on the release rate of the drug were investigated. In addition, dissolution rate, as well as weight loss of silica xerogel, was evaluated. In general, both the lyophilizing process of xerogels and the increase in size of non-lyophilizing device significantly decrease both the rate of drug release and the rate of dissolution of matrix. The overall release process was found to be governed by diffusion control and simultaneous zero-order dissolution of the xerogel.

Silica-antibiotic hybrid nanoparticles for targeting intracellular pathogens

We investigated the capability of biodegradable silica xerogel as a novel carrier of antibiotic and the efficacy of treatment compared to that with the same dose of free drug against murine salmonellosis. The drug molecules (31%) entrapped in the sol-gel matrix remained in biologically active form, and the bactericidal effect was retained upon drug release. The in vitro drug release profiles of the gentamicin from the xerogel and that from the xerogel-polyethylene glycol (PEG) were distinctly different at pH 7.4. A delayed release of gentamicin was observed from the silica xerogel network (57% in 33 h), and with the addition of 2% PEG, the release rate reached 90% in 33 h. Administration of two doses of the silica xerogel significantly reduced the Salmonella enterica serovar Typhimurium load in the spleens and livers of infected AJ 646 mice. The silica xerogel and xerogel-PEG achieved a 0.45-log and a 0.41-log reduction in the spleens, respectively, while for the free drug there was no reduction. On the other hand, silica xerogel and xerogel-PEG achieved statistically significant 1.13-log and 1.15-log reductions in the livers, respectively, while for the free drug the reduction was a nonsignificant value of 0.07 log. This new approach, which utilizes a room-temperature synthetic route for incorporating therapeutic drugs into the silica matrix, should improve the capability for targeting intracellular pathogens.

Silica xerogels as pharmaceutical drug carriers

This review focuses on silica xerogels obtained by the sol-gel method and their application as drug delivery systems. SiO(2) xerogels are potential biomaterials to be used as matrix materials for the extended and controlled release of different kinds of biologically active agents administered by various routes. The article includes some representative examples that describe the encapsulation of bioactive molecules and model compounds inside a silica matrix produced by the conventional sol-gel method or by ultrasound hydrolysis. The drug release rate from xerogels could be modified by adjusting several parameters, such as the type of precursor, the concentration of the catalyst and drying temperature. In vitro and in vivo studies have shown the efficacy and biodegradability of these composites. The potential application of silica xerogels as drug carrier systems is critically analyzed and discussed.