Nanoarchitectonics of nitric oxide releasing supramolecular structures for enhanced antibacterial efficacy under visible light irradiation.

Light-controlled therapies offer a promising strategy to prevent and suppress infections caused by numerous bacterial pathogens. Excitation of exogenously supplied photosensitizers (PS) at specific wavelengths elicits levels of reactive oxygen intermediates toxic to bacteria. Porphyrin-based supramolecular nanostructure frameworks (SNF) are effective PS with unique physicochemical properties that have led to their widespread use in photomedicine. Herein, we developed a nitric oxide (NO) releasing, biocompatible, and stable porphyrin-based SNF (SNF-NO), which was achieved through a confined noncovalent self-assembly process based on π-π stacking. Characterization of the SNFs via scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis showed the formation of three-dimensional, well-defined octahedral structures. These SNF-NO were shown to exhibit a red shift due to the noncovalent self-assembly of porphyrins, which also show extended light absorption to broadly cover the entire visible light spectrum to enhance photodynamic therapy (PDT). Under visible light irradiation (46 J cm-2), the SNF generates high yields of singlet oxygen (1O2) radicals, hydroxyl radicals (HO), superoxide radicals (O2), and peroxynitrite (ONOO-) radicals that have shown potential to enhance antimicrobial photodynamic therapy (APDT) against Gram-positive methicillin-resistant Staphylococcus aureus (MRSA) and Gram-negative Escherichia coli (E. coli). The resulting SNFs also exhibit significant biofilm dispersion and a decrease in biomass production. The combination of robust photosensitizer SNFs with nitric oxide-releasing capabilities is dynamic in its ability to target pathogenic infections while remaining nontoxic to mammalian cells. The engineered SNFs have enormous potential for treating and managing microbial infections.

Tethered Liquid Perfluorocarbon Coating for 72 Hour Heparin-Free Extracorporeal Life Support.

Coagulopathic complications during extracorporeal life support (ECLS) result from two parallel processes: 1) foreign surface contact and shear stress during blood circulation and 2) administration of anticoagulant drugs to prevent circuit thrombosis. To address these problems, biocompatible surfaces are developed to prevent foreign surface-induced coagulopathy, reducing or eliminating the need for anticoagulants. Tethered liquid perfluorocarbon (TLP) is a nonadhesive coating that prevents adsorption of plasma proteins and thrombus deposition. We examined application of TLP to complete ECLS circuits (membranes, tubing, pumps, and catheters) during 72 hours of ECLS in healthy swine (n = 5/group). We compared TLP-coated circuits used without systemic anticoagulation to standard of care: heparin-coated circuits with continuous heparin infusion. Coagulopathic complications, device performance, and systemic effects were assessed. We hypothesized that TLP reduces circuit thrombosis and iatrogenic bleeding, without impeding gas exchange performance or causing untoward effects. No difference in bleeding or thrombotic complication rate was observed; however, circuit occlusion occurred in both groups (TLP = 2/5; CTRL = 1/5). TLP required elevated sweep gas rate to maintain normocapnia during ECLS versus CTRL (10-20 vs. 5 L/min; p = 0.047), suggesting impaired gas exchange. Thrombus deposition and protein adhesion on explanted membranes were comparable, and TLP did not preserve platelet or blood cell counts relative to controls. We conclude that neither TLP nor standard of care is an efficacious solution to prevent coagulation disturbances during ECLS. Further testing of promising biomaterials for ECLS utilizing the model outlined here is warranted.

Antibacterial and Cellular Response Toward a Gasotransmitter-Based Hybrid Wound Dressing.

Biological processes such as infection, angiogenesis, and fibroblast proliferation and migration need to be regulated for effective healing of a wound. Failing to do so can delay the overall wound healing and add to the suffering and healthcare cost. Endogenous nitric oxide (NO) is a well-known gasotransmitter in the natural healing process in humans and other mammals. To utilize its inherent ability in the current study, an exogenous NO donor (S-nitroso-glutathione, GSNO) was integrated into a hybrid formulation consisting of a natural polymer (alginate) and a synthetic polymer (poly(vinyl alcohol) (PVA)). The alginate-PVA-GSNO dressings showed a sustained NO release for 72 h that resulted in 99.89 ± 0.40% and 98.93 ± 0.69% eradication of Staphylococcus aureus and Pseudomonas aeruginosa, respectively, which are among the most common causal agents of wound infections. The designed dressings resulted in a 3-fold increase in the proliferation of human endothelial cells when compared with control without GSNO showing its angiogenic potential. In addition, mouse fibroblast cells exposed to leachates from alginate-PVA-GSNO dressings showed significantly higher proliferation when compared to control alginate-PVA showing the NO release from exogenous GSNO in fibroblast proliferation. Fibroblast migration was shown to be much faster with GSNO-based dressings when compared to corresponding control dressings resulting in complete closure of an in vitro wound model within 48 h. The porous dressings also possessed important physical properties such as swelling, water vapor transmission, and moisture content that are desirable for effective wound healing. Overall, this study supports the possibility of using therapeutic alginate-PVA-GSNO dressing to provide a supportive environment for accelerated wound healing.

Catalyzed Nitric Oxide Release Via Cu Nanoparticles Leads to an Increase in Antimicrobial Effects and Hemocompatibility for Short Term Extracorporeal Circulation.

Devices used for extracorporeal circulation are met with two major medical concerns: thrombosis and infection. A device that allows for anticoagulant-free circulation while reducing risk of infection has yet to be developed. We report the use of a copper nanoparticle (Cu NP) catalyst for the release of nitric oxide (NO) from the endogenous donor S-nitrosoglutathione (GSNO) in a coating applied to commercial Tygon S3™ E-3603 poly(vinyl chloride) tubing in order to reduce adhered bacterial viability and the occurrence thrombosis for the first time in an animal model. Cu GSNO coated material demonstrated a nitric oxide (NO) release flux ranging from an initial flux of 6.3 ± 0.9 ×10-10 mol cm-2 min-1 to 7.1 ± 0.4 ×10-10 mol cm-2 min-1 after 4 h of release, while GSNO loops without Cu NPs only ranged from an initial flux of 1.1 ± 0.2 ×10-10 mol cm-2 min-1 to 2.3 ± 0.2 ×10-10 mol cm-2 min-1 after 4 h of release, indicating that the addition of Cu NPs can increase NO flux up to five times in the same 4 h period. Additionally, a 3-log reduction in S. aureus and 1-log reduction in P. aeruginosa was observed in viable bacterial adhesion over a 24 h period compared to control loops. A Cell Counting Kit-8 (CCK-8) assay was used to validate no overall cytotoxicity towards 3T3 mouse fibroblasts. Finally, extracorporeal circuits were coated and exposed to 4 h of blood flow under an in vivo rabbit model. The Cu GSNO combination was successful in maintaining 89.3% of baseline platelet counts, while the control loops were able to maintain 67.6% of the baseline. These results suggest that the combination of Cu NPs with GSNO increases hemocompatibility and antimicrobial properties of ECC loops without any cytotoxic effects towards mammalian cells.