Small molecule inhibitors of the SARS-CoV Nsp15 endoribonuclease

The severe acute respiratory syndrome (SARS) virus encodes several unusual RNA processing enzymes, including Nsp15, an endoribonuclease that preferentially cleaves 3’ of uridylates through a ribonuclease A (RNase A)-like mechanism. Crystal structures of Nsp15 confirmed that the Nsp15 active site is structurally similar to that of RNase A. These similarities and our molecular docking analysis lead us to hypothesize that previously characterized RNase A inhibitors will also inhibit the SARS-CoV Nsp15. Benzopurpurin B, C-467929, C-473872, N-306711, N-65828, N-103019 and congo red were tested for effects on Nsp15 endoribonuclease activity. A fluorescence assay revealed that the IC50 values for inhibiting endoribonuclease activity were between 0.2 µM and 40 µM. These compounds were demonstrated to bind SARS-CoV Nsp15 by a differential scanning fluorimetry assay. Benzopurpurin B also inhibited the endoribonuclease activities of the Nsp15 orthologs from two other coronaviruses: mouse hepatitis virus (MHV) and infectious bronchitis virus (IBV). Benzopurpurin B, C-473872, and congo red reduced infectivity of MHV in L2 cells by 8- to 26- fold. The more effective drugs caused a decrease in MHV RNA accumulation. All three compounds reduced the infectivity of the SARS-CoV in Vero cells

Novel Transthyretin Amyloid Fibril Formation Inhibitors: Synthesis, Biological Evaluation, and X-Ray Structural Analysis

Transthyretin (TTR) is one of thirty non-homologous proteins whose misfolding, dissociation, aggregation, and deposition is linked to human amyloid diseases. Previous studies have identified that TTR amyloidogenesis can be inhibited through stabilization of the native tetramer state by small molecule binding to the thyroid hormone sites of TTR. We have evaluated a new series of β-aminoxypropionic acids (compounds 5–21), with a single aromatic moiety (aryl or fluorenyl) linked through a flexible oxime tether to a carboxylic acid. These compounds are structurally distinct from the native ligand thyroxine and typical halogenated biaryl NSAID-like inhibitors to avoid off-target hormonal or anti-inflammatory activity. Based on an in vitro fibril formation assay, five of these compounds showed significant inhibition of TTR amyloidogenesis, with two fluorenyl compounds displaying inhibitor efficacy comparable to the well-known TTR inhibitor diflunisal. Fluorenyl 15 is the most potent compound in this series and importantly does not show off-target anti-inflammatory activity. Crystal structures of the TTR∶inhibitor complexes, in agreement with molecular docking studies, revealed that the aromatic moiety, linked to the sp(2)-hybridized oxime carbon, specifically directed the ligand in either a forward or reverse binding mode. Compared to the aryl family members, the bulkier fluorenyl analogs achieved more extensive interactions with the binding pockets of TTR and demonstrated better inhibitory activity in the fibril formation assay. Preliminary optimization efforts are described that focused on replacement of the C-terminal acid in both the aryl and fluorenyl series (compounds 22–32). The compounds presented here constitute a new class of TTR inhibitors that may hold promise in treating amyloid diseases associated with TTR misfolding

Collagen-functionalized electrospun smooth and porous polymeric scaffolds for the development of human skin-equivalent

Electrospun polymer fibers have garnered substantial importance in regenerative medicine owing to their intrinsic 3D topography, extracellular matrix microenvironment, biochemical flexibility, and mechanical support. In particular, a material's nano-topography can have a significant effect on cellular responses, including adhesion, proliferation, differentiation, and migration. In this study, poly(L-lactic acid) (PLLA), a biodegradable polymer with excellent biocompatibility was electrospun into fibers with either smooth or porous topologies. The scaffolds were further modified and biofunctionalized with 0.01% and 0.1% collagen to enhance bioactivity and improve cellular interactions. Human keratinocytes (HaCaTs) and fibroblasts (human foreskin fibroblasts-HFF) were cultured on the scaffolds using a modified co-culture technique, where keratinocytes were grown on the dorsal plane for 5 days, followed by flipping, seeding with fibroblasts on the ventral plane and culturing for a further 5 days. Following this, cellular adhesion of the skin cells on both the unmodified and collagen-modified scaffolds (smooth and porous) was performed using scanning electron microscopy (SEM) and immunofluorescence. Distinct outcomes were observed with the unmodified smooth scaffolds showing superior cell adhesion than the porous scaffolds. Modification of the porous and smooth scaffolds with 0.1% collagen enhanced the adhesion and migration of both keratinocytes and fibroblasts to these scaffolds. Further, the collagen-modified scaffolds (both porous and smooth) produced confluent and uniform epidermal sheets of keratinocytes on one plane with healthy fibroblasts populated within the scaffolds. Thus, presenting a vast potential to serve as a self-organized skin substitute this may be a promising biomaterial for development as a dressing for patients suffering from wounds.Aswathy Ravindran Girija, Vivekanandan Palaninathan, Xanthe Strudwick, Sivakumar Balasubramanian, Sakthikumar Dasappan Nair and Allison J. Cowi

Collagen Functionalization of Polymeric Electrospun Scaffolds to Improve Integration into Full-Thickness Wounds.

BACKGROUND: Electrospun fibers are widely studied in regenerative medicine for their ability to mimic the extracellular matrix (ECM) and provide mechanical support. In vitro studies indicated that cell adhesion and migration is superior on smooth poly(L-lactic acid) (PLLA) electrospun scaffolds and porous scaffolds once biofunctionalized with collagen. METHODS: The in vivo performance of PLLA scaffolds with modified topology and collagen biofunctionalization in full-thickness mouse wounds was assessed by cellular infiltration, wound closure and re-epithelialization and ECM deposition. RESULTS: Early indications suggested unmodified, smooth PLLA scaffolds perform poorly, with limited cellular infiltration and matrix deposition around the scaffold, the largest wound area, a significantly larger panniculus gape, and lowest re-epithelialization; however, by day 14, no significant differences were observed. Collagen biofunctionalization may improve healing, as collagen-functionalized smooth scaffolds were smallest overall, and collagen-functionalized porous scaffolds were smaller than non-functionalized porous scaffolds; the highest re-epithelialization was observed in wounds treated with collagen-functionalized scaffolds. CONCLUSION: Our results suggest that limited incorporation of smooth PLLA scaffolds into the healing wound occurs, and that altering surface topology, particularly by utilizing collagen biofunctionalization, may improve healing. The differing performance of the unmodified scaffolds in the in vitro versus in vivo studies demonstrates the importance of preclinical testing.Aswathy Ravindran Girija, Xanthe Strudwick, Sivakumar Balasubramanian, Vivekanandan Palaninathan, Sakthikumar Dasappan Nair, and Allison J. Cowi

Extremophilic polysaccharide for biosynthesis and passivation of gold nanoparticles and photothermal ablation of cancer cells

Extremophiles are the group of organisms that are far overlooked for exploring novel biomaterials in the field of material science and bionanotechnology. Extremophilic bacterial-sulfated exopolysaccharide, mauran (MR), is employed for the bioreduction and passivation of gold nanoparticles (AuNps) to enhance the biocompatibility of AuNps and used for photothermal ablation of cancer cells. Here, various concentrations of MR solution are tested for the reduction of HAuCl4 solution in the presence as well as in the absence of an external reducing agent, to produce mauran-gold nanoparticles (MRAu Nps). These biocompatible nanocomposites are treated with cancer cell lines under in vitro conditions and NIR irradiated for complete ablation. MRAu Nps-treated cancer cells on immediate exposure to infrared radiation from a femtosecond pulse laser of operating wavelength 800 nm are subjected to hyperthermia causing cell death. Biocompatible MR stabilization could fairly reduce the cytotoxicity caused by bare AuNps during biomedical applications. Application of a biocompatible polysaccharide from extremophilic bacterial origin for reduction and passivation of AuNps and used for a biomedical purpose is known to be first of its kind in bionanofusion studies

Novel Transthyretin Amyloid Fibril Formation Inhibitors: Synthesis, Biological Evaluation, and X-Ray Structural Analysis

Transthyretin (TTR) is one of thirty non-homologous proteins whose misfolding, dissocn., aggregation, and deposition is linked to human amyloid diseases. Previous studies have identified that TTR amyloidogenesis can be inhibited through stabilization of the native tetramer state by small mol. binding to the thyroid hormone sites of TTR. We have evaluated a new series of b-aminoxypropionic acids (compds. 5-21), with a single arom. moiety (aryl or fluorenyl) linked through a flexible oxime tether to a carboxylic acid. These compds. are structurally distinct from the native ligand thyroxine and typical halogenated biaryl NSAID-like inhibitors to avoid off-target hormonal or anti-inflammatory activity. Based on an in vitro fibril formation assay, five of these compds. showed significant inhibition of TTR amyloidogenesis, with two fluorenyl compds. displaying inhibitor efficacy comparable to the well-known TTR inhibitor diflunisal. Fluorenyl 15 is the most potent compd. in this series and importantly does not show off-target antiinflammatory activity. Crystal structures of the TTR:inhibitor complexes, in agreement with mol. docking studies, revealed that the arom. moiety, linked to the sp2-hybridized oxime carbon, specifically directed the ligand in either a forward or reverse binding mode. Compared to the aryl family members, the bulkier fluorenyl analogs achieved more extensive interactions with the binding pockets of TTR and demonstrated better inhibitory activity in the fibril formation assay. Preliminary optimization efforts are described that focused on replacement of the C-terminal acid in both the aryl and fluorenyl series (compds. 22-32). The compds. presented here constitute a new class of TTR inhibitors that may hold promise in treating amyloid diseases assocd. with TTR misfolding