In this work, we report a smart stimuli-responsive drug delivery system (DDS) that can release drug depending upon the amount of pathogen (MRSA) present in the target. A greater amount of MRSA in the system will lead to more release of drug and vice versa. Carbon-dot-coated novel alginate beads (CA-CD) exhibiting superior stability was successfully used as smart drug delivery vehicle. Garlic extract (GE), which contains allicin, was taken as model drug system to demonstrate the phenomena. It was observed that GE loading was 19 and 78% with CA and CA-CD, respectively. CA-CD-GE shows pH-dependent controlled drug release, which results in increased therapeutic efficiency. CA-CD-GE is not only stimuli responsive but also a controlled drug release system as it releases drug according to the pathogen concentration (MRSA). All the three factors viz. drug release, MRSA concentration and pH of the medium are interdependent as when the cell divides, it produces secondary metabolites that lead to the decrease in pH of the medium. The drop in the pH value triggers drug release from the beads. And the effect of the drug is reflected by the MRSA cell death. Hence, we demonstrate a smart stimuli responsive DDS. However, such DDS will be useful in cases where increased amount of pathogen in the system will lead to reduction in pH.

Mutagenic and Carcinogenic substances are a threat to any living organism, and its detection is of paramount importance. In this work, we fabricate for the first time a DNA-carbon dots based electrochemical biosensor for sensitive and selective detection of mutagenic nitrosamines like N-nitrosodimethylamine (NDMA) and N-nitrosodiethanolamine (NDEA). At first, on the glassy carbon electrode (GCE), chitosan carbon dot was deposited, then, DNA was electro-statically immobilizing on the surface of carbon dots to fabricate the sensing electrode (DNA/chiCD/GCE modified electrode). In the presence of NDMA and NDEA, in differential pulse voltammetry technique, the absolute peak current increases, and thus it can detect NDMA and NDEA. The system DNA/chiCD/GCE modified electrode is highly selective and sensitive toward NDMA and NDEA. The detection limit was determined to be 9.9 × 10–9 M and 9.6 × 10–9 M, respectively. The possible reason for DNA/chiCD/GCE modified electrode showing such electrochemical selectivity toward nitrosamines is investigated and discussed.

In this work chitosan carbon dot (chiCD) based fluorescence sensor was developed which can selectively detect Retinoic acid (RA). The CDs were prepared from chitosan hydrogel and further conjugated with NaF to develop a chiCD‐NaF system for the detection of Retinoic acid based on its PL properties. It was found that addition of NaF resulted in the enhancement of fluorescent spectra of ChiCD. Addition of RA to the chiCD‐NaF system resulted in quenching of the PL spectra. The detection of RA was selective as there is no change in PL properties using other vitamins viz. ascorbic acid, choelcalciferol, Folic acid, Riboflavin, Tocopherol etc. The chiCD‐NaF systems were also checked with two commercially available capsule containing mixtures of vitamins and here too PL change was insignificant demonstrating selectivity of RA. A probable mechanistic behaviour of the system towards different vitamins is also explained in this paper.

In this work a paper carbon dot (PCDs) based fluorescence sensor was developed which can distinguish between the organic and inorganic sulphur in analytes.

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