Synthesis of Fluorescent Nanoparticles and Bacteria-Nanoparticle Conjugates for Targeted Delivery of Cancer Therapeutics

Abstract

The effectiveness of clinical chemotherapy and radiotherapy has been associated primarily with the resistance at the cellular level and availability of oxygen. There is substantial evidence, which suggests that the mechanisms that involve tumor microenvironment also facilitate resistance to solid tumors to chemotherapy. The aforementioned limitation can be surmounted by combinatorial approaches where two or more therapeutic strategies supplement each other and improve the quality of the treatment. So far, bacteriotherapy; the use of bacteria or bacterial products for the treatment of cancer and, nanotechnology; the use of nanoscale materials as therapeutic or carrier of therapeutics have been proved as much safer approach with minimal side effects compared to conventional therapies. Keeping these mentioned perspectives as major challenges, facultative anaerobic Lactobacillus spp. were selected along with fluorescent nanoparticles to develop an alternative therapeutic approach for cancer. The present thesis reports three scientific contributions pertaining to the development of the bacteria-nanoparticle and drug-loaded nanoparticles separately for the delivery of the theraputics. Fluorescent cadmium sulfide (CdS) nanoparticles of ~20 nm were synthesized using bacterial extracellular polymers (EPS) and glucose separately using reductive chemistry biomolecules. However, fluorescent perylenediimide derivative doped silica (Si) nanoparticles of ~30 nm were synthesized using sol-gel method and developed as core-shell nanoparticles where PLGA was coated to the surface of Si nanoparticles. The UV-vis spectrophotometry, XRD, AFM, FESEM, and TEM analysis confirmed the formation of nanoscale particles. FTIR and 1H-NMR studies further confirmed the formation of a core-shell structure suitable for drug delivery. The bacteria-nanoparticle conjugates and drug-loaded nanoparticles were developed using synthesized CdS and Si nanoparticles. The internalization of CdS and Si nanoparticles by Lactobacillus spp. and development of microbots (bacteria carrying nanoparticles) was demonstrated. The chemical interaction of bacteria-nanoparticles was studied by FTIR, FESEM and confocal laser scanning microscopy (CLSM). Simultaneously, development of drug-loaded nanoparticles was carried out by loading anticancer doxorubicin (DOX) drug in hybrid PLGA-Si nanoparticles that was further confirmed by FTIR, NMR and fluorescence spectrophotometry. Finally, the efficacy of developed microbots in human cancer cell lines (Caco-2 and MCF-7) along with synthesized nanoparticles and mentioned Lactobacillus spp. was studied. The efficiency of Cd and Si-based microbots was analyzed by FESEM and CLSM, which confirmed the successful internalization of bacteria in cancer cells and deliverance of nanoparticles. The efficacy of microbots was found to be better than bacteria alone due to the internalized nanoparticles. Whereas, cell metabolic activity assay, colocalization and study of the drug-loaded NPs by CLSM and two-photon microscopy demonstrates a highly effective therapeutic approach for the delivery of doxorubicin by hybrid PLGA-Si nanoparticles into the cell organelles.