Biodegradable Polymeric Microparticles in Biomedical Applications

Nisin-loaded chitosan/sodium alginate microspheres enhance the antimicrobial efficacy of nisin against Staphylococcus aureus

AIMS

To develop and evaluate nisin-loaded chitosan/sodium alginate (CS/SA) microspheres as an improved antimicrobial delivery system targeting Staphylococcus aureus strains.

METHODS AND RESULTS

The microspheres were prepared using a modified water-in-oil emulsion cross-linking method, resulting in spherical particles sized 1-8 µm with a surface charge of -7.92 ± 5.09 mV, confirmed by scanning electron microscopy (SEM) and Zetasizer analysis. Encapsulation efficiency (EE) and loading capacity (LC) of nisin were 87.60% ± 0.43% and 1.99% ± 0.01%, respectively. In vitro release studies over 48 h indicated a controlled release pattern of nisin, described by the Korsmeyer-Peppas model, with higher release rates at 37°C and alkaline pH. Antimicrobial assays showed an enhanced efficacy of nisin-loaded CS/SA microspheres compared to free nisin, with minimum inhibitory concentration values reduced by 50%. Confocal laser scanning microscopy (CLSM), SEM, and transmission electron microscopy showed significant bacterial membrane damage and cellular disruption induced by the microspheres.

CONCLUSIONS

This study highlights the potential of nisin-loaded CS/SA microspheres as an innovative antimicrobial delivery system with improved stability and antimicrobial efficacy against S. aureus, addressing limitations associated with nisin applied alone.

Pancreatic tumor microenvironmental acidosis and hypoxia transform gold nanorods into cell-penetrant particles for potent radiosensitization

Coating nanoparticles with stealth epilayers increases circulation time by evading opsonization, macrophage phagocytosis, and reticuloendothelial sequestration. However, this also reduces internalization by cancer cells upon reaching the tumor. We designed gold nanorods (GNRs) with an epilayer that retains stealth properties in circulation but transforms spontaneously in the acidotic tumor microenvironment to a cell-penetrating particle. We used a customized stoichiometric ratio of l-glutamic acid and l-lysine within an amphiphilic polymer of poly(l-glutamic acid-co-l-lysine), or P(Glu-co-Lys), to effect this transformation in acidotic environments. P(Glu-co-Lys)-GNRs were internalized by cancer cells to facilitate potent in vitro radiosensitization. When administered intravenously in mice, they accumulate in the periphery and core of tumors without any signs of serum biochemical or hematological alterations, normal organ histopathological abnormalities, or overt deterioration in animal health. Furthermore, P(Glu-co-Lys)-GNRs penetrated the tumor microenvironment to accumulate in the hypoxic cores of tumors to potently radiosensitize heterotopic and orthotopic pancreatic cancers in vivo.

Preparation of Polysaccharide-Based Microspheres by a Water-in-Oil Emulsion Solvent Diffusion Method for Drug Carriers

Polysaccharide-based microspheres of chitosan, starch, and alginate were prepared by the water-in-oil emulsion solvent diffusion method for use as drug carriers. Blue dextran was used as a water-soluble biomacromolecular drug model. Scanning electron microscopy showed sizes of the resultant microspheres that were approximately 100 μm or less. They were spherical in shape with a rough surface and good dispersibility. Microsphere matrices were shown as a sponge. Drug loading efficiencies of all the microspheres were higher than 80%, which suggested that this method has potential to prepare polysaccharide-based microspheres containing a biomacromolecular drug model for drug delivery applications.