Gisela Solange Alvarez

Antibiotic-loaded silica nanoparticle–collagen composite hydrogels with prolonged antimicrobial activity for wound infection prevention

Silica-collagen type I nanocomposite hydrogels are evaluated as medicated dressings to prevent infection in chronic wounds. Two antibiotics, gentamicin and rifamycin, are encapsulated in a single step within plain silica nanoparticles. Their antimicrobial efficiency against Pseudomonas aeruginosa and Staphylococcus aureus is assessed. Gentamycin-loaded 500 nm particles can be immobilized at high silica dose in concentrated collagen hydrogels without modifying their fibrillar structure or impacting on their rheological behavior and increases their proteolytic stability. Gentamicin release from the nanocomposites is sustained over 7 days, offering an unparalleled prolonged antibacterial activity. Particle immobilization also decreases their cytotoxicity towards surface-seeded fibroblast cells. Rifamycin-loaded 100 nm particles significantly alter the collagen hydrogel structure at high silica doses. The thus-obtained nanocomposites show no antibacterial efficiency, due to strong adsorption of rifamycin on collagen fibers. The complex interplay of interactions between drugs, silica and collagen is a key factor regulating the properties of these composite hydrogels as antibiotic-delivering biological dressings and must be taken into account for future extension to other wound healing agents.

A functional material that combines the Cr(VI) reduction activity of Burkholderia sp. with the adsorbent capacity of sol–gel materials

In the present work, Cr(VI) reduction in aqueous as well as in soil environments has been studied using free and sol–gel immobilized Burkholderia sp. Enhanced reduction rates were achieved by immobilized cells, which are found to be protected from the deleterious effects of high Cr(VI) concentrations. Immobilized bacteria showed enhanced performance in comparison with free cells because of the combination of bacteria biotransformation effect and chromium adsorption on silica matrices. Moreover, bacteria did not lose any activity after four cycles of reutilization. Bacteria immobilized in silica matrices had the ability to completely reduce 100 µg ml−1Cr(VI) after 4 days of incubation in aqueous media and to transform 200 µg ml−1Cr(VI) after 7 days in sterile soil. Immobilized bacteria demonstrated highly efficient Cr(VI) reduction over the Cr(VI) concentration range 50–500 µg g−1 and 200–800 µg g−1 in aqueous and soil environments, respectively. These results highlight the potential of this functional material that combines the biological activity of bacterial cells with the adsorbent capacity of sol–gel materials.

Development of Sol-Gel Hybrid Materials for Whole Cell Immobilization

The development of a good biocompatible matrix for immobilization of cells is very crucial for improving the performance of functional biohybrids. The synthesis of solid inorganic materials from alkoxide, aqueous and polyol-modified silanes routes, as well as the incorporation of organic polymers, are further areas being developed to improve the viability of encapsulated cells. This emerging field of material science has generated considerable and increasing interest during the past decade. Recent advances in the field involving biomaterials, biohybrids, and functional nanomaterials provided novel materials, which have gained the attention of the scientific community, Governments and industrial companies. Overall, this review is intended to give an overview on the current state of the art of the patents associated to the immobilization of whole living cells in sol-gel derived hybrid materials and to describe the major challenges to be addressed in the forthcoming years.

Recent patents on the synthesis and application of silica nanoparticles for drug delivery.

Drug delivery systems are designed to improve therapy efficacy as well as patient compliance. This could be accomplished by specifically targeting a medication intact to its active site, therefore reducing side-effects and enabling high local drug concentrations. Silica nanoparticles have gained ground in the biomedical field for their biocompatibility and biodegradability, being themselves inert and stable, thus enabling a variety of formulation designs for application in the pharmaceutical industry. This paper is a review of the recent patents on the applications of silica nanoparticles for drug delivery and their preparation. The review will focus on the different techniques available to obtain silica nanoparticles with variable morphology and their drug targeting applications, providing an overview of silica particles synthesis described in the literature.

Sol-gel Encapsulation of Biomolecules and Cells for Medicinal Applications

The sol-gel process provides a robust and versatile technology for the immobilization of biologicals. A wide range of inorganic, composites and hybrid materials can be prepared to encapsulate molecular drugs, proteins, antibodies/antigens, enzymes, nucleic acids, prokaryotic and eukaryotic cells into bulk gels, particles and films. This review describes the applications of sol-gel encapsulation relevant to medicinal chemistry focusing on the recent development of biosensors as well as systems for production, screening and delivery of bioactive compounds and biomaterials.

Production of monoclonal antibodies from hybridoma cells immobilized in 3D sol–gel silica matrices

The immobilization of mammalian cells in suitable matrices that can retain their viability and capability to produce certain metabolites has gained attention in recent years. In this work, hybridoma cells were immobilized in sol–gel silica matrices for in vitro production of monoclonal antibodies. For that purpose, different matrices were evaluated in terms of cell viability, antibody diffusion to surrounding media and physicochemical properties of the polymeric material. Tetrakis (2-ethoxyethyl) orthosilicate (THEOS) matrices were found to be the best option for hybridoma immobilization. The concentrations of the silica precursor as well as the number of immobilized cells were also optimized. Three hundred mM of THEOS precursor and 5 × 105 hybridoma cells appear to be the most suitable alternative. Hybridoma cells immobilized in THEOS matrices were able to produce monoclonal antibodies to the same extent as free cells, thus introducing the possibility of using them in the design of bioreactors for large-scale production.

A new method for the preparation of biocompatible silica coated-collagen hydrogels

Silica-collagen scaffolds were obtained by covalent binding of an aminosilane to glutaraldehyde fixed collagen hydrogels, rendering a three dimensional network of silicon coated collagen fibrils. When compared to non-silicified collagen, silica containing matrices exhibited a 60 fold increment in the rheological properties. Moreover, acellular degradation by collagenase type I indicated that enzymatic digestion occurred at a slower rate for silica modified hydrogels, hence enabling a controlled degradation of the obtained material. In addition, fibroblastic cells seeded on silicified collagen matrices were able to adhere, proliferate and migrate within the scaffold for over 3 weeks as shown by MTT tests and hematoxylin-eosin staining. These results suggest that the herein described method could be useful in the design of materials for tissue engineering purposes.

Advances in collagen, chitosan and silica biomaterials for oral tissue regeneration: from basics to clinical trials

Different materials have distinct surface and bulk characteristics; each of them potentially useful for the treatment of a particular wound or disease. By reviewing those materials that have reached a clinical stage the reader will have a broad panorama of the possibilities a particular material can offer, regarding its ability to support fast tissue regeneration. This review covers the most recent advances made towards the development of biomaterials aimed to support regenerative processes. Indeed, we highlight key examples, from basic research to clinical trials, of biomaterials for a specific biomedical application. In this context, the focus is made on collagen, chitosan and silica which are key representatives of a protein, a polysaccharide and an inorganic material usually employed as biomaterials. Particularly, this review article presents an overview of their potential therapeutics in the treatment of disorders within the oral mucosa and tooth supporting tissues. Finally, the importance of in vivo and in vitro studies, clinical evidence studies, systematic reviews and meta-analyses as an adequate guidance for biomaterial design and development is highlighted.

Silica core–shell particles for the dual delivery of gentamicin and rifamycin antibiotics

Increasing bacterial resistance calls for the simultaneous delivery of multiple antibiotics. One strategy is to design a unique pharmaceutical carrier that is able to incorporate several drugs with different physico-chemical properties. This is highly challenging as it may require the development of compartmentalization approaches. Here we have prepared core-shell silica particles allowing for the dual delivery of gentamicin and rifamycin. The effect of silica particle surface functionalization on antibiotic sorption was first studied, enlightening the role of electrostatic and hydrophobic interactions. This in turn dictates the chemical conditions for shell deposition and further sorption of these antibiotics. In particular, the silica shell deposition was favored by the positively charged layer of gentamicin coating on the core particle surface. Shell modification by thiol groups finally allowed for rifamycin sorption. The antibacterial activity of the core-shell particles against Staphylococcus aureus and Pseudomonas aeruginosa demonstrated the dual release and action of the two antibiotics.

Nanoparticles and capillary electrophoresis: A marriage with environmental impact

The impact of nanomaterials in the environment and human health is a cause of big concern and even though intensive studies are currently being carried out, there is still a lot to elucidate. The development of validated methods for the characterization and quantification of nanomaterials and their impact on the environment should be encouraged to achieve a proper, safe, and sustainable use of nanoparticles (NPs). Recently, CE emerged as a well‐adapted technique for the analysis of environmental samples. This review presents the application of NPs together with CE systems for environmental pollutants analysis, as well as the application of CE techniques for the analysis of various types of NPs.