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Excessive use of food coloring agents in the food industry to make the food more attractive or improve the taste has caused various health and ecological problems. Therefore, it is necessary to develop a reliable, sensitive, and selective sensing probe to detect food dyes in different food products for future industrial processing and biosafety. In recent decades, surface-functionalized quantum dots (QDs), owing to their unique optical properties, have gained tremendous interest for a wide range of applications, including biomedical, bioimaging and sensing applications. Herein, we have reported the synthesis of excellent colloidal stable and highly luminescent CdTe core and CdTe@ZnTe core–shell QDs using dual functionalizing agents, polyvinyl pyrrolidone and vitamin C. The synthesized QDs were explored as excellent sensing probes for the food dyes carmoisine, Ponceau 4R and tartrazine with limit of detection (LOD) values of 0.097 ± 0.006, 0.147 ± 0.001 and 0.044 ± 0.001 μM for CdTe–PVP QDs and 0.079 ± 0.001, 0.114 ± 0.002 and 0.042 ± 0.001 μM for CdTe@ZnTe–PVP QDs, respectively. The sensitivity of the synthesized QDs for the food dyes was also investigated in real samples (soft drinks and medications). Moreover, considering the potential effects of QDs as therapeutics or nano-drug carriers, the interactions between the synthesized QDs and carrier protein human serum albumin (HSA) were investigated. The binding affinity was observed to be in the order of 104 M−1. QDs were found to quench the intrinsic fluorescence of HSA, and both types of quenching (static and dynamic) occur via electrostatic interactions in association with hydrophobic forces without any significant alteration in the protein structure. [ABSTRACT FROM AUTHOR]

Studying the interactions of bioactive phenolic acids [ferulic acid (FA), caffeic acid (CA), and chlorogenic acid (CGA)] with the carrier protein bovine hemoglobin (BHb) helps to understand their modes of binding and transport, which affect their bioavailability. The protein–ligand complexes exhibited binding constants (Kb) in the range of 104 M−1, indicating a reversible mode of association. BHb–CA complexation attenuated the inherent fluorescence of BHb (β2-Trp37 dominant fluorophore) through a static quenching mechanism. However, a combined (static and dynamic) quenching mechanism was observed for the BHb–FA/CGA complexes. In this study, the thermodynamic parameter, ΔG°, determined from fluorescence spectroscopy, was negative, suggesting that the complexation of BHb with phenolic acids was spontaneous. The negative change in enthalpy [ΔH° = –(8.539 ± 1.331) kJ mol−1, –(10.620 ± 1.028) kJ mol−1, and –(8.637 ± 0.232) kJ mol−1 for BHb–FA, BHb–CA, BHb–CGA complexes, respectively] and positive entropy change [ΔS° = + (63.862 ± 1.218) J mol−1 K−1, +(67.108 ± 1.681) J mol−1 K−1, and +(62.540 ± 1.058) J mol−1 K−1 for BHb–FA, BHb–CA, BHb–CGA complexes, respectively] indicated that hydrogen bonding and hydrophobic forces stabilized the complexes. Computational studies also illustrated similar interactive forces in BHb–ligand complexes. Changes around the microenvironment of the Trp residues in the binding process were verified using various spectral measurements. Circular dichroism and Fourier infrared spectroscopies illustrated a decrease in the α-helical content of BHb during complexation. Fibril inhibition properties of the ligands were verified using ThT assay, ANS binding studies, Congo Red assay, turbidity assay, Soret absorption measurements, and CD spectral measurements. The structure–activity relationship, binding affinity, and interactive forces between the protein and phenolic acids could explain the order of anti-fibrillation properties. [ABSTRACT FROM AUTHOR]

In recent decades, Cd-based quantum dots (QDs) have gained tremendous interest as luminescence tags for numerous biological applications. However, chemical synthesis using organic molecules to encapsulate the QDs surface is a highly complex process, high-cost and aggressive fabrication, and less aqueous and biocompatible, which leads to restricted biological applications. In this paper, we have reported the biogenic synthesis of CdSe-HSA core and CdSe@ZnSe-HSA core–shell QDs for the first time using human serum albumin protein as a surface engineering molecule. The biosynthesized QDs were found to be smaller in size (2–3.5 nm) and highly aqueous compatible (stable for up to 150 days). The biosynthesized QDs act as ultrasensitive fluorescence probes for label-free sensing of Hg2+ with enhanced efficiency, and an LOD value of 1.3 nM for CdSe@ZnSe-HSA QDs (concentration range: 0–2 μM) was obtained and were also able to detect with the naked eye. A dynamic quenching mechanism was observed for the fluorescence quenching of the biosynthesized QDs by Hg2+ ions, and affinity toward the formation of Hg–Se or Hg–SH with the QDs provided the unique selectivity. Moreover, the smaller size and unique surface properties of the biosynthesized QDs contributed to the enhanced antibacterial properties against Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria and found more effective against Gram-negative bacteria. This work implies the biogenic aqueous compatible synthesis of core and core–shell QDs for biological and environmental monitoring analytical methods for the development of bionanotechnology. [ABSTRACT FROM AUTHOR]

This study focuses on synthesizing an injectable and self-healing hydrogel from an abundant serum protein (bovine serum albumin, BSA) to control antimicrobial drug delivery impeding bacterial infections. Hydrogels were synthesized through a green synthesis route without using any crosslinking agent and characterized for their cross-linking, surface morphology, self-healing, viscoelasticity, injectability, and swelling and degradation properties. The prepared hydrogel has distinctive autofluorescence properties, as observed from the wavelength-dependent steady-state fluorescence spectral measurements. When lomefloxacin and doxycycline were incorporated into the hydrogel network, it allowed the controlled release of both antibiotics over at least 24 hours, with a release rate of over 90%. Hydrogels containing lomefloxacin and doxycycline were effectively used against E. coli and E. faecalis bacterial strains; their antibacterial effects were maintained for 24 hours. The live/dead cell test indicated that the hydrogel is effective against both (Gram-positive and Gram-negative) bacteria strains. Furthermore, our studies on bacteria encapsulation, specifically using E. coli, confirmed that the hydrogel is non-toxic, and the hydrogel demonstrates biocompatibility as the bacteria successfully grow within the hydrogel matrix. To assess biocompatibility, we conducted a cell attachment experiment with HEK 293 cells, and the results suggest that this hydrogel could be used for 3D cell culturing in the future. [ABSTRACT FROM AUTHOR]

In recent decades, polysaccharide-based hydrogels have gained significant attention due to their natural biocompatibility, biodegradability, and non-toxicity. The potential for using polysaccharides to synthesize hydrogels is due to their ability to support cell proliferation, which is important for practical applications, particularly in the biomedical field. In this study, we have synthesized a chitosan-α-naphthal hydrogel film using a cost-effective one-step synthesis approach. The prepared hydrogel film exhibited high encapsulation efficiency for antibacterial drugs such as ciprofloxacin and lomefloxacin, with the ability to release the antibiotics in a controlled manner over an extended period and prevent long-term bacterial infections. Moreover, the Korsmeyer and Peppas power law, based on Fickian diffusion, was employed to model the entire complex drug release process and predict the drug release behavior. The hydrogel film also shows pH-induced swelling ability due to the presence of an imine bond in the hydrogel network, which is degradable at acidic pH. The incorporated therapeutic agents having antibacterial activity were effective against Gram-negative ( Escherichia coli DH5α ) and Gram-positive ( Staphylococcus aureus subsp. aureus ) bacterial strains. A wound dressing material should possess mechanical strength, but the prepared hydrogel film has low mechanical strength. To increase the mechanical strength, we have infused pineapple leaf fibers (PLFs) in the film network, resulting in a mechanical strength of 1.12 ± 0.89 MPa. In addition to its mechanical strength, significant cell viability against human embryonic kidney (HEK-293) cells was observed from in vitro cell culture experiments for this PLF-hydrogel film. As a result, the prepared therapeutic agent-loaded hydrogel film under study meets the requirements to be considered for use as a wound dressing material.