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The successful treatment of multi-drug resistant microbial pathogens represents a major challenge for public health management. Here, chitosan-alginate (CS/ALG) microspheres with narrow size distribution were fabricated by ionically cross linking method using Ca2+ ions as agents for polymer solidification. The physicochemical properties of CS/ALG microspheres, such as surface morphology and size, were studied by SEM. The functional group interactions were confirmed by Fourier transform infrared (FTIR) spectroscopy. SEM revealed that the CS/ALG microspheres were spherical in shape with smooth surfaces, size was 50–100 μm. The synthesized CS/ALG microspheres showed antibacterial and antibiofilm activity on bacteria of public health relevance. CS/ALG microspheres exhibited antibacterial activity at the concentration of 5–20 μg, with significant inhibitory zones on multiple antibiotic resistant pathogens, including Gram positive Staphylococcus aureus, Enterococcus faecalis, and Gram negative Pseudomonas aeruginosa and Proteus vulgaris. Furthermore, in situ light microscopy and confocal laser scanning microscopy (CLSM) showed that CS/ALG microspheres inhibited the bacterial biofilm formation in S. aureus, E. faecalis P. aeruginosa and P. vulgaris after a single treatment with 40 μg. Overall, our findings underlined that chemically synthesized CS/ALG biomaterial has high antibacterial and antibiofilm activity against a number of microbial pathogens of interest for human health, thus this synthesis route can be further exploited for drug development in current biomedical science.

Antimicrobial peptide crustin was isolated and purified from Penaeus semisulcatus using Sephadox G-100 column gel filtration chromatography. P. semisulcatus crustins was observed as a single band with 14 kDa of molecular weight on SDS-PAGE and the retention time of 46 min in RP-HPLC. Circular dichroism spectra of P. semisulcatus crustin showed alpha helices in its secondary structure followed by random coils. Crystalline nature and functional groups arrangement were investigated by X-Ray Diffraction (XRD) and Fourier Transform Infra-Red spectroscopy (FTIR). P. semisulcatus crustin showed the effective antibacterial activity against Gram positive strains B. thuringienisis (4 μg/ml) and B. pumilis (6 μg/ml) when compare to Gram negative strains. Biofilm Inhibitory Concentration (BIC) were determined for these strains and percentage of biofilm inhibition was confirmed and visualized through in sit microscopic analysis. Hence, we reported the effect of crustin on biofilm inhibition and eradication at low concentrations by using crystal violet staining and confocal microscopic observations. In addition, haemolytic activity of this purified crustin also analysed using human RBCs. The results of this study, suggests that this bio peptide crustin is a potential and promising therapeutic agent to treat drug resistant bacteria and biofilm-related infections.

Ruta graveolens silver nanoparticles (AgNPs) showed the color change within 30 min and characterized using UV–visible spectra, Fourier Transform Infrared (FTIR), X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). UV–visible spectrum of R. graveolens AgNPs showed the sharp peak at the wavelength of 440–560 nm. XRD patterns confirmed that crystalline nature of R. graveolens AgNPs and FTIR results revealed that phytochemical reaction of these R. graveolens is responsible for the synthesis of AgNPs. TEM results showed the size of the R. graveolens AgNPs around 30–50 nm with spherical and triangular nature. Further, the antibacterial and antibiofilm activity of R. graveolens AgNPs showed the effective inhibitory activity against clinically important Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans. Our findings suggest that R. graveolens AgNPs can be exploited toward the development of potential antibacterial agents for various biomedical and environmental applications.