In Situ Photo-crosslinkable Hyaluronic Acid/Gelatin Hydrogel for Local Nitric Oxide Delivery.

An increasing number of studies have shown that the local release of nitric oxide (NO) from hydrogels stimulates tissue regeneration by modulating cell proliferation, angiogenesis, and inflammation. The potential biomedical uses of NO-releasing hydrogels can be expanded by enabling their application in a fluid state, followed by controlled gelation triggered by an external factor. In this study, we engineered a hydrogel composed of methacrylated hyaluronic acid (HAGMA) and thiolated gelatin (GELSH) with the capacity for in situ photo-cross-linking, coupled with localized NO release. To ensure a gradual and sustained NO release, we charged the hydrogels with poly(l-lactic-co-glycolic acid) (PLGA) nanoparticles functionalized with S-nitrosoglutathione (GSNO), safeguarding SNO group integrity during photo-cross-linking. The formation of thiol-ene bonds via the reaction between GELSH's thiol groups and HAGMA's vinyl groups substantially accelerated gelation (by a factor of 6) and increased the elastic modulus of hydrated hydrogels (by 1.9-2.4 times). HAGMA/GELSH hydrogels consistently released NO over a 14 day duration, with the release of NO depending on the hydrogels' equilibrium swelling degree, determined by the GELSH-to-HAGMA ratio. Biocompatibility assessments confirmed the suitability of these hydrogels for biological applications as they display low cytotoxicity and stimulated fibroblast adhesion and proliferation. In conclusion, in situ photo-cross-linkable HAGMA/GELSH hydrogels, loaded with PLGA-GSNO nanoparticles, present a promising avenue for achieving localized and sustained NO delivery in tissue regeneration applications.

Antimicrobial efficacy of a nitric oxide-releasing ampicillin conjugate catheter lock solution on clinically-isolated antibiotic-resistant bacteria.

Antibiotic lock therapy (ALT) is standard clinical practice for treating bacteremia linked with catheter-related bloodstream infections (CRBSIs). However, this strategy frequently fails against multi-drug-resistant bacteria in clinical settings. In this study, a novel approach to utilize a nitric oxide (NO) donor S-nitroso-N-acetyl-penicillamine (SNAP)-conjugated to ampicillin antibiotic (namely SNAPicillin) as a catheter lock solution is presented. The conjugate of two antimicrobial agents is anticipated to overcome the challenges of bacterial infection caused by antibiotic-resistant bacteria in ALT applications. Nitric oxide release from the SNAPicillin lock solution at varying concentrations was measured at 0 and 24 h time points in a catheter model system, which revealed tunable NO release at physiological levels. The clinical strains of E. coli (CDC AR-0089) and S. marcescens (CDC AR-0099) were screened using a zone of inhibition assay against standard antibiotics which confirmed the antibiotic resistance in bacteria. The minimum inhibitory concentration (MIC) testing of SNAPicillin unveiled the lowest MIC value for SNAPicillin against both E. coli and S. marcescens (1 and 2 mM of SNAPicillin, respectively) with an 8.24- and 4.28-log reduction in bacterial load compared to controls, respectively. In addition, while the ampicillin-treated biofilm demonstrated resistance toward the antibiotic, SNAPicillin led to >99% reduction in exterminating biofilm buildup on polymeric catheter surfaces. Lastly, the SNAPicillin lock solution was determined to be biocompatible via hemolysis and cell compatibility studies. Together, these results emphasize the promising potential of SNAPicillin lock solution with the dual-action of NO and ampicillin in overcoming bacterial challenges on medical devices like central venous catheters and other medical device interfaces.

A Multidisciplinary Experiment to Characterize Antifouling Biocompatible Interfaces via Quantification of Surface Protein Adsorption.

Novel biomaterial development is a rapidly growing field that is crucial because biomaterial fouling, due to rapid and irreversible protein adsorption, leads to cellular responses and potentially detrimental consequences such as surface thrombosis, biofilm formation, or inflammation. Therefore, biomaterial technology's fundamentals, like material biocompatibility, are critical in undergraduate education. Exposing undergraduate students to biomaterials and biomedical engineering through interdisciplinary experiments allows them to integrate knowledge from different fields to analyze multidisciplinary results. In this practical laboratory experiment, undergraduate students will characterize surface properties (contact and sliding angle measurements) for the antifouling polydimethylsiloxane (PDMS) polymer using a goniometer and a smartphone, as well as quantify protein adsorption on antifouling surfaces via a colorimetric assay kit to develop their understanding of antifouling surface characteristics, UV-vis spectroscopy, and colorimetric assays. The antifouling PDMS polymer is prepared by silicone oil infusion and compared to untreated control PDMS. The polymer hydrophobicity was demonstrated by static water contact angles of ~99° and 102° for control and antifouling PDMS surfaces, respectively. The control PDMS sliding angle (>90°) was significantly reduced to 9° after antifouling preparation. After 24 h incubation of polymer samples in a 200 mg/mL bovine serum albumin (BSA) solution, the surface adsorbed BSA was quantified using a colorimetric assay. The adsorbed protein on the fouling PDMS controls (29.1 ± 7.0 µg/cm2) was reduced by ~79% on the antifouling PDMS surface (6.2 ± 0.9 µg/cm2). Students will gain experience in materials science, biomedical engineering, chemistry, and biology concepts and better understand the influence of material properties on biological responses for biomaterial interfaces.