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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.

Marine ecosystem is a treasure house of drugs as a plenty of marine organisms possess interesting bioactive properties that has to be explored further to find applications in the biomedical and pharmaceutical arena. Sea urchin is a seafloor dwelling invertebrate belonging to the phylum Echinodermata is having high nutritional and medicinal properties. It is rich in vitamins, minerals, proteins, fatty acids and polysaccharides and possess anticancer, anticoagulant/antithrombotic, antimicrobial and antioxidant properties. The extracts and hydrolysates of sea urchin have various bioactive compounds especially glycosides, acid polysaccharide, sphingoid, glycolipids, sulphate,​ polysaccharides and phospholipids. Owing to its wide range of biomedical properties, the present review aims to summarize the therapeutic applications of valuable bioactive components in sea urchins. This review could act as a key reference to identify the new potential bioactive molecules in the drug industry and unravels the applications of sea urchin.

1,5-Dihydroxyanthraquinone (1,5-DHAQ) can form an inclusion complex with β-cyclodextrin (β-CD) strong base in aqueous solution, which can be employed to solubilize and stabilize the 1,5-DHAQ in pH 11 solution (1,5-DHAQ−2H;probe L). The hydrophobic nature of β-CD helps to dissolve and stabilize the probe L and hence permits its use as a probe in coordination reactions with cations and anions. This inclusion complex (β-CD:1,5-DHAQ−2H; probe LC) has been used for the colorimetric recognition behavior towards the Cu2+ and Cr2O72− ions by changing the color of the solution, which could be easily observed with the naked eye detection. Probe LC showed good fluorescence behavior upon interaction with different metal ions displayed strong fluorescence quenching (∼80%; switch-Off) with Cu2+ while remaining silent toward the tested cations. Moreover, that the LC Cu2+ ensemble when tested toward different anions only dichromate (Cr2O72−) enable copper coordination (as CuCr2O7) and led to fluorescence enhancement (∼84%; switch-On). The detection limits of sensor LC to Cu2+ and LC Cu2+ complex to Cr2O72− anion were estimated to be 10 nM and 0.8 nM, respectively. A theoretical study on molecular docking and density functional theory (DFT) calculations has been performed to demonstrate the binding of Cu2+ to Cr2O72− ions with probe LC. Furthermore, the propensity of probe LC as a bio-imaging fluorescent probe to detect Cu2+ ion and sequential detection of Cr2O72− ion by LC Cu2+ in living cells (human lung cancer A549) by confocal laser scanning microscopy.

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.