RESUMO
The continuous rise in bacterial infections and antibiotic resistance is the driving force behind the search for new antibacterial agents with novel modes of action. Antimicrobial peptides (AMPs) have recently gained attention as promising antibiotic agents with the potential to treat drug-resistant infections. Several AMPs have shown a lower propensity towards developing resistance compared to conventional antibiotics. However, these peptides, especially acyldepsipeptides (ADEPs) present with unfavorable pharmacokinetic properties, such as high toxicity and low bioavailability. Different ways to improve these peptides to be drug-like molecules have been explored, and these include using biocompatible nano-carriers. ADEP1 analogues (SC005-8) conjugated to gelatin-capped Silver/Indium/Sulfide (AgInS2) quantum dots (QDs) improved the antibacterial activity against Gram-negative (Escherichia coli and Pseudomonas aeruginosa), and Gram-positive (Bacillus subtilis, Staphylococcus aureus and Methicillin-resistant Staphylococcus aureus) bacteria. The ADEP1 analogues exhibited minimum inhibition concentrations (MIC) between 63 and 500 µM, and minimum bactericidal concentrations (MBC) values between 125 and 750 µM. The AgInS2-ADEP1 analogue conjugates showed enhanced antibacterial activity as evident from the MIC and MBC values, i.e., 1.6-25 µM and 6.3-100 µM, respectively. The AgInS2-ADEP1 analogue conjugates were non-toxic against HEK-293 cells at concentrations that showed antibacterial activity. The findings reported herein could be helpful in the development of antibacterial treatment strategies.
RESUMO
The poor fluorescence properties of magneto-fluorescent paramagnetic-ion (Gd, Mn, or Co) doped I-III-VI quantum dots (QDs) at higher paramagnetic-ion doping concentrations have limited their use in magnetic-driven water-based applications. This work presents, for the first time, the use of stable magneto-fluorescent Gd-doped AgInS2 QDs at high Gd mole ratios of 16, 20, and 30 for the fluorescence detection and adsorption of Ag+ ions in water environments. The effect of pH, initial concentration, contact time, and adsorbent dosage were systematically evaluated. The AgInS2 QDs with the least Gd mole ratio (16) exhibited the best fluorescence characteristics (LOD = 0.88, R2 = 0.9549) while all materials showed good adsorption properties under optimized conditions (pH of 2, initial concentration of 30 ppm, contact time of 10 min and adsorbent dosage of 0.02 g) and a pseudo 2nd order reaction was followed. The adsorption mechanism was proposed to be a combination of ion-exchange, electrostatic interaction, complexation, and diffusion processes. Application in environmental wastewater samples revealed complete removal of Ag + ions alongside Ti2+ Pb2+, Ni2+, Cr3+, and Zn2+ ions.
RESUMO
Heavy metal contamination remains a major threat to the environment. Evaluating the concentrations of heavy metals in water environments is a crucial step towards a viable treatment strategy. Non-cadmium photo-luminescent I-III-VI ternary QDs have attracted increasing attention due to their low toxicity and extraordinary optical properties, which have made them popular in biological applications. Recently, ternary I-III-VI-QDs have gained growing interest as fluorescent detectors of heavy metal ions in water. Here, we review the research progress of ternary I-III-VI QDs for the fluorescence detection of heavy metal ions in water. First, we summarize the optical properties and synthesis methodologies of ternary I-III-VI QDs. Then, we present various detection mechanisms involved in the fluorescence detection of heavy metal ions, which are mostly attributed to direct interaction between these unique QDs and the metal ions, seen in the form of fluorescence quenching and fluorescence enhancement. We also display the potential applications in environmental remediation such as water treatment and associated challenges of I-III-VI QDs in the fluorescence detection of Cu2+ and other metal ions.