Peptide- and Drug-Functionalized Fluorescent Quantum Dots for Enhanced Cell Internalization and Bacterial Debilitation

Abstract

This report illustrates a strategy for designing a nanoconjugate derived vector that efficiently delivers antimicrobial drug directly into bacterial cells. The nanoconjugate comprises of negatively charged CDTe@CdS quantum dots (QDs) with its surface functionalized using cationic BP-100 (KKLFKKILKYL-amide), a known cell-penetrating peptide (CPP), via electrostatic approach. The interactions between QD and CPP in QD-functionalized CPPs (QD-CPP) have been well analyzed using fluorescence spectroscopy, gel electrophoresis, and ζ-potential analysis. The QD-CPP conjugate was internalized into Gram negative (<i>Escherichia coli</i>) as well as Gram positive (<i>Staphylococcus aureus</i>) bacterial strains with confocal studies exhibiting a strong signal in tested microorganisms. Further, to check the applicability of QD-CPP conjugate as a delivery vector for generating an effective therapeutics, ampicillin molecules were conjugated on QD-CPP surface to generate QD-CPP-Amp conjugate. The CPP and drug molecules on the surface of QDs were well quantified using high-performance liquid chromatography (HPLC) data. It was observed that the internalization and bacterial debilitation of the QD-CPP-Amp conjugate is 2- to 4-fold effective as compared to that of bare ampicillin. The morphological changes to the bacterial cells upon the treatment with QD-CPP-Amp conjugates were noted with no cytotoxic effect on tested mammalian cell lines. The results inferred that the proposed QD-CPP vector provides a targeted and proficient approach for cellular internalization of cargo (drug) in bacterial cells with effective tracking through florescent QDs.