Innovative utilization of harvested mushroom substrate for green synthesis of silver nanoparticles: A multi-response optimization approach.

In this work, harvested mushroom substrate (HMS) has been explored for the first time through a comprehensive optimization study for the green synthesis of silver nanoparticles (AgNPs). A multiple response central composite design with three parameters: pH of the reaction mixture, temperature, and incubation period at three distinct levels was employed in the optimization study. The particle size of AgNPs, UV absorbance, and the percentage of Ag/Cl elemental ratio were considered as the response parameters. For each response variable examined the model used was found to be significant (P < 0.05). The ideal conditions were: pH 8.9, a temperature of 59.4 °C, and an incubation period of 48.5 h. The UV-visible spectra of AgNPs indicated that the absorption maxima for AgNP-3 were 414 nm, 420 for AgNPs-2, and 457 for AgNPs-1. The XRD analysis of AgNPs-3 and AgNPs-2 show a large diffraction peak at ∼38.2°, ∼44.2°, ∼64.4°, and ∼77.4°, respectively, which relate to the planes of polycrystalline face-centered cubic (fcc) silver. Additionally, the XRD result of AgNPs-1, reveals diffraction characteristics of AgCl planes (111, 200, 220, 311, 222, and 400). The TEM investigations indicated that the smallest particles were synthesized at pH 9 with average diameters of 35 ± 6 nm (AgNPs-3). The zeta potentials of the AgNPs are -36 (AgNPs-3), -28 (AgNPs-2), and -19 (AgNPs-1) mV, respectively. The distinct IR peak at 3400, 1634, and 1383 cm-1 indicated the typical vibration of phenols, proteins, and alkaloids, respectively. The AgNPs were further evaluated against gram (+) strain Bacillus subtilis (MTCC 736) and gram (-) strain Escherichia coli (MTCC 68). All of the NPs tested positive for antibacterial activity against both bacterial strains. The study makes a sustainable alternative to disposing of HMS to achieve the Sustainable Development Goals (SDGs).

3-Polythiophene Acetic Acid Nanosphere Anchored Few-Layer Graphene Nanocomposites for Label-Free Electrochemical Immunosensing of Liver Cancer Biomarker.

This study devised a label-free electrochemical immunosensor for the quantitative detection of alpha-fetoprotein (AFP). 3-Polythiophene acetic acid (3-PTAA) nanoparticles were anchored onto a few-layer graphene (FLG) nanosheet, and the resulting nanocomposite was utilized as the immunosensor platform. The AFP antibody (anti-AFP) was immobilized on 3-PTAA@FLG via a covalent interaction between the amine group of anti-AFP and the carboxylic group of 3-PTAA via ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC)/N-hydroxysuccinimide (NHS) coupling. FLG is largely responsible for providing electrochemical signals, whereas 3-PTAA nanoparticles are well-known for their ability to be compatible with biological molecules in neutral aqueous solutions. Moreover, the carboxyl group present in 3-PTAA effectively binds anti-AFP through EDC/NHS conjugation. Owing to good dispersibility and higher surface area of 3-PTAA, it is very convenient for casting the polymer directly on the electrode substrate followed by immobilization of anti-AFP. Thus, it is feasible to regulate the activity of AFP proteins and control the spatial distribution of the immobilized anti-AFP proteins. The electrochemical sensing performance was assessed via cyclic voltammetry and electrochemical impedance spectroscopy. For an increase in the bioconjugate concentration, the results demonstrated a surge in charge-transfer resistance and a consequent decline in the current response. This approach effectively detected AFP at an extended dynamic range of 0.0001-250 ng/mL with a detection limit of 0.047 pg/mL. Furthermore, the sensing capacity of the immunosensor for AFP detection has been demonstrated to be steady in real human serum cultures. Our approach exhibits good electrochemical performance in terms of reproducibility, selectivity, and stability, which would surely impart budding applications in the clinical diagnosis of several other tumor markers.

Asymmetric fabrication and in vivo evaluation of the wound healing potency of electrospun biomimetic nanofibrous scaffolds based on collagen crosslinked modified-chitosan and graphene oxide quantum dot nanocomposites.

Asymmetric scaffolds were developed through electrospinning by utilizing biocompatible materials for effective wound healing applications. First of all, the chitosan surface was modified with decanoyl chloride and crosslinked with collagen to synthesize collagen crosslinked modified-chitosan (CG-cross-CS-g-Dc). Then, the asymmetric scaffolds were fabricated through electrospinning, where the top layer was a monoaxial nanofiber of the PCL/graphene oxide quantum dot (GOQD) nanocomposite and the bottom layer was a coaxial nanofiber having PCL in the core and the CG-cross-CS-g-Dc/GOQD nanocomposite in the shell layer. The formation of monoaxial (∼130 ± 50 nm) and coaxial (∼320 ± 40 nm) nanofibers was confirmed by transmission electron microscopy (TEM). The presence of GOQDs contributed to antioxidant and antimicrobial efficacy. These scaffolds showed substantial antibacterial activity against the common wound pathogens Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The scaffolds exhibited excellent cytocompatibility (MTT assay) and anti-inflammatory behaviour as analysed via the cytokine assay and biochemical analysis. The in vivo wound healing potential of the nanofibrous scaffolds was assessed with full-thickness excisional wounds in a rat model. The scaffolds accelerated the re-epithelialization as well as the collagen deposition, thereby facilitating the wound healing process in a very short span of time (10 days). Both in vitro and in vivo analyses thus provide a compelling argument for the use of these scaffolds as therapeutic biomaterials and their suitability for application in rapid wound regeneration and repair.