Sub-cytotoxic doses of pharmaceutical silica nanoparticles show significant impact on the proteome of HepG2 cells

Nanoparticle Fraught Liposomes: A Platform for Increased Antibiotic Selectivity in Multidrug Resistant Bacteria

Increasing antibiotic concentrations within bacterial cells while reducing them in mammalian ones would ultimately result in an enhancement of antibacterial actions, overcoming multidrug resistance, all while minimizing toxicity. Nanoparticles (NPs) have been used in numerous occasions to overcome antibiotic resistance, poor drug solubility, and stability. However, the concomitant increase in antibiotic concentration in mammalian cells and the resultant toxicity are usually overlooked. Without compromising bacterial cell fusion, large liposomes (Lip) have been reported to show reduced uptake in mammalian cells. Therefore, in this work, small NP fraught liposomes (NP-Lip) were formulated with the aim of increasing NP uptake and antibiotic delivery in bacterial cells but not in mammalian ones. Small polylactic-co-glycolic acid NPs were therefore loaded with erythromycin (Er), an antibiotic with low membrane permeability that is susceptible to drug efflux, and 3c, a 5-cyanothiazolyl urea derivative with low solubility and stability. In vitro experiments demonstrated that the incorporation of small NPs into large Lip resulted in a reduction in NP uptake by HEK293 cells while increasing it in Gram-negative bacteria (Escherichia coli DH5α, E. coli K12, and Pseudomonas aeruginosa), consequently resulting in an enhancement of antibiotic selectivity by fourfold toward E. coli (both strains) and eightfold toward P. aeruginosa. Ocular administration of NP-Lip in a P. aeruginosa keratitis mouse model demonstrated the ability of Er/3c-loaded NP-Lip to result in a complete recovery. More importantly, in comparison to NPs, the ocular administration of NP-Lip showed a reduction in TNF-alpha and IL-6 levels, implying reduced interaction with mammalian cells in vivo. This work therefore clearly demonstrated how tailoring the nano-bio interaction could result in selective drug delivery and a reduction in toxicity.

Influence of silica nanoparticles on cadmium-induced cytotoxicity, oxidative stress, and apoptosis in human liver HepG2 cells

Extensive application of amorphous silica nanoparticles (Si NPs) and ubiquitous cadmium (Cd) may increase their chances of coexposure to humans. Studies on combined effects of Si NPs and Cd in human cells are very limited. We investigated the potential mechanism of toxicity caused by coexposure of amorphous Si NPs and Cd in human liver (HepG2) cells. Results showed that Si NPs were not toxic to HepG2. However, Cd induced significant toxicity in HepG2 cells. Interestingly, we observed that a noncytotoxic concentration of Si NPs potentiated the cytotoxicity of Cd in HepG2 cells. We further noticed that coexposure of Si NPs and Cd augmented oxidative stress evidenced by the generation of oxidants (reactive oxygen species, hydrogen peroxide, and lipid peroxidation) and depletion of antioxidants (glutathione level and antioxidant enzyme activity). Coexposure of Si NPs and Cd also augmented mitochondria-mediated apoptosis in HepG2 cells indicated by altered regulation of apoptotic genes (p53, bax, bcl-2, caspase-3, and caspase-9) along with reduced mitochondrial membrane potential. Interaction data indicated that Si NPs facilitate the cellular uptake of Cd due to its strong adsorption on the surface of Si NPs. Hence, Si NPs increased the bioaccumulation and toxicity of Cd in HepG2 cells. This study warrants further research to explore the potential mechanisms of combined toxicity of Si NPs and Cd in animal models.