(575d) Novel Nano Biotechnology Approaches for Treating Intracellular Bacterial Infections

Bacterial infections were once easily treatable illnesses but are increasingly becoming a serious world health epidemic. Rising antibiotic resistance is making current treatments obsolete and even effective antibiotics are inadequate when bacteria invade the host’s cells and create a persistent or chronic infection.

To combat an intracellular infection, we developed two novel antimicrobial treatments: light activated nanoparticles and gene-specific antisense molecules. Light activated cadmium telluride (CdTe) quantum dots are precisely tuned nanoparticles that treat infectious agents by increasing the reactive oxygen species (ROS) content exposed to the bacteria to its lethal threshold while remaining below the host cells’ toxic ROS limit. Due to the CdTe nanoparticles 2-4 nm diameter they are small enough to penetrate the host cell membrane, bacteria vacuole, and bacteria membrane to easily treat intracellular infections. Secondly, here we show a gene-specific antisense therapy using peptide nucleic acids (PNA) can offer a precise method of targeting and treating intracellular infections. PNA therapeutics can be designed to target numerous essential genes unique to a specific bacterium of interest without effecting non-infectious bacteria.

Here we establish an infection model using Salmonella enterica serovar Typhimurium in two mammalian cells lines, the epithelial HeLa cell line and osteoblast precursor MC3T3-E1 cell line, to test our two novel antimicrobial treatments and their effect on the host cells. Salmonella is a common microbe seen in infections that readily infects numerous different cells lines using its type three secretion system (T3SS) and remains intracellular in a protective salmonella containing vacuole. Exogenously added quantum dots show tunable clearance and limited host cell toxicity by modulating the concentration and light intensity, correlating to the quantum dots’ ROS production. PNA therapeutic molecules when added using bacterial secretion systems, also show tunable intracellular clearance based on concentration and gene specificity with limited host cell toxicity.

These results demonstrate two new antimicrobial treatments to combat intracellular infections and establish an infection model to further explore these therapeutics on different combinations of intracellular infections and host cells representing various pertinent clinical infection challenges.