Green synthesis of silver nanoparticles from discarded shells of velvet tamarind (Dialium cochinchinense) and their antimicrobial synergistic potentials and biofilm inhibition properties.

In the field of nanomedicine, biogenic metal nanoparticles are commonly synthesized using edible plant products as bio-reducing or stabilizing agents. In this study, discarded shell of velvet tamarind fruit is explored as a potent reducing agent for biogenic synthesis of silver nanoparticles (VeV-AgNPs). Silver nanoparticles were formed in minutes under sunlight exposure, which was considerably fast compared to under ambient conditions. The optical, structural and morphological studies revealed that the nanoparticle colloidal solution consisted of particles with quasi-spherical and rodlike morphologies. To investigate antimicrobial properties, eight microorganisms were exposed to the VeV-AgNPs. The results indicated that VeV-AgNPs had enhanced antimicrobial activity, with a recorded minimum inhibitory concentration (MIC) of 3.9 µg/mL against E. coli. Further studies were conducted to examine the biofilm inhibition properties and synergistic effect of the VeV-AgNPs. The findings showed a biofilm inhibition potential of around 98% against E. coli, and the particles were also found to increase the efficacy of standard antimicrobial agents. The combinatory effect with standard antifungal and antibacterial agents ranged from synergistic to antagonistic effects against the tested microorganisms. These results suggest that silver nanoparticles produced from discarded shells of velvet tamarind are potent and could be used as a potential drug candidate to combat antimicrobial resistance.

Green synthesis of silver nanoparticles from peel extract of Chrysophyllum albidum fruit and their antimicrobial synergistic potentials and biofilm inhibition properties.

Current methods for green synthesis of metal nanoparticles often require continuous harvesting of fresh bio-materials for every synthesis cycle. Practices and procedures that economize bio-materials need to be employed if green synthesis could become a sustainable and eco-friendly method for synthesizing metal nanoparticles. This study explores Chrysophyllum albidum peels (mostly regarded as waste) to prepare silver nanoparticles (Alb-AgNPs). The technique employed in the synthesis allows repeated use of the peels, thus, reducing the heavy dependence on bio-materials. The optical and structural properties of the Alb-AgNPs were studied with Scanning electron microscope, Fourier transform infrared spectrometer, UV-Vis spectrophotometer and powder X-ray diffractometer. The antimicrobial properties of the Alb-AgNPs were studied with selected microorganisms namely; S. aureus, E. coli, K. pneumoniae, B. subtilis, S. mutans, P. aeruginosa, S. typhi, and Candida albicans. High inhibitory activity against the microorganisms were exhibited with MICs ranging from 15.62 to 1000 µg/mL. Again, the Alb-AgNPs showed the ability to enhance the efficacy of standard antimicrobial agents. The results of the combined interaction with standard antibacterial and antifungal agents ranged from synergistic to antagonistic effects against the tested microorganisms. In addition, the Alb-AgNPs could serve as a biofilm inhibitor with the highest percent inhibition of about 92% against methicillin-resistant Staphylococcus aureus. The results from this study thus provide access to the simple, sustainable, economic and eco-friendly synthesis of silver nanoparticles with efficient antimicrobial properties as drug candidates as a means of overcoming the prevailing antibiotic resistance menaces.

Ultrasensitive and recyclable superstructure of AuSiO2@Ag wire for surface-enhanced Raman scattering detection of thiocyanate in urine and human serum.

Thiocyanate level in the human system can serve as a biomarker to distinguish smokers from non-smokers. Thiocyanate is a potential goitrogen, thus an accurate determination may help to identify lactating mothers with high thiocyanate dosage, thereby preventing the transport of excess SCN- to infants. Surface-enhanced Raman spectroscopy has become a versatile and reliable technique to detect SCN- in different media. However, the conventional surface-enhanced Raman scattering (SERS) substrates used to detect SCN- are often discarded after use. The frequent disposal of such metal nanoparticles is detrimental to the environment and makes the SERS-based detection of SCN- uneconomical. In this study, we present fabrication of a new, ultrasensitive and recyclable SERS substrate, based on an AuSiO2@Ag wire (W) superstructure, to detect SCN- in different media. The hierarchical AuSiO2@AgW substrate was obtained by forming nano-sized patches of SiO2 on micron-sized AgW and anchoring 30 nm-sized gold nanoparticles on the patches with mercaptopropyltrimethoxysilane. This ultrasensitive substrate could detect SCN- at a low concentration of 0.001 µM in water, and 0.01 µM in urine and human serum. In addition, a facile procedure to regenerate and recycle the SCN- bound AuSiO2@AgW platform in different media has been demonstrated. The insight gained in the present study can serve as a promising and powerful method for fabrication of active and recyclable substrates for SERS-based detection of SCN-.