Arginine decorated nanocarriers exhibited intravacuolar targeting capability which was utilized to deliver antibiotics into the intracellular niche of pathogens like Salmonella and Mycobacterium. The arginine based nanocarrier system (Arg-MSN) was developed on a mesoporous silica nanoparticle (MSN) template by conjugating L-arginine to protamine and pectin coated MSN by using a layer-by-layer coating approach. The synthesized nanocarriers were characterized using microscopy, FTIR spectroscopy, and zeta potential analyses. Lower cytotoxicity and hemolysis was observed for Arg-MSN nanocarrier compared to bare MSN template. Ciprofloxacin, a fluoroquinolone antibiotic was entrapped in Arg-MSN which showed gradual release of ciprofloxacin over a period of 24 h. In vitro experiments in Salmonella infected macrophages and epithelial cells exhibited two-fold higher antibacterial activity with ciprofloxacin-loaded Arg-MSN (Cip Arg-MSN) compared to free ciprofloxacin. The increased antibacterial activity of Cip Arg-MSN is believed to result from co-localization of Arg-MSN with the intravacuolar Salmonella and localized delivery of the antibiotic. We also observe an increase in reactive nitrogen species upon Arg-MSN treatment in the infected cells. In vivo bacterial burden and morbidity studies exhibited nearly ten-fold lower Salmonella burden in the infected organs such as spleen, liver and MLN (mesenteric lymph nodes). Similar survival rates were observed at a lower dosage of Cip Arg-MSN over free ciprofloxacin. The coordinated effect of improved antibiotic delivery, intracellular targeting and production of reactive nitrogen species was found to result in enhanced antibacterial activity. The developed Arg-MSN system is expected to be an attractive carrier system for delivery of antibiotics for clearing intravacuolar infections.Scheme 1 Schematic representation depicting arginine grafted mesoporous silica nanoparticle (Arg-MSN) targeting intracellular Salmonella ensuring antibiotic delivery (ciprofloxacin) at the intracellular niche to achieve improved therapeutic outcomes in vitro and in vivo. The role of reactive nitrogen intermediates and co-localization of particles with the intracellular Salmonella containing vacuole improves the anti-bacterial effect (image mice: https://www.jax.org/strain/000651). This journal isFig. 1 Characterization of the mesoporous silica nanoparticle. High resolution transmission electron microscopy images of (A) bare MSN; (B) Arg-MSN, coating around the MSN is shown by yellow arrows (C) dynamic light scattering size spectrum of Arg-MSN. (D) Zeta potential of cumulative deposition of polyelectrolyte layers. (E) Adsorption-desorption isotherm of bare MSN. (F) Pore size distribution of bare MSN by BET method. Scale bar for TEM images is 50 nm. 7024 | RSC Adv., 2017, 7, 7022-7032 This journal is

Lipid coated mesoporous silica nanoparticle (L-MSN) were synthesized for oral delivery of ciprofloxacin for intracellular elimination of Salmonella pathogen. The particle size was found to be between 50-100 nm with a lipid coat of approximately 5 nm thickness. The lipid coating was achieved by sonication of liposomes with the MSN particles and evaluated by CLSM and FTIR studies. The L-MSN particles exhibited lower cytotoxicity compared to bare MSN particles. Ciprofloxacin, a fluoroquinolone antibiotic, loaded into the L-MSN particles showed enhanced antibacterial activity against free drug in in vitro assays. The lipid coat was found to aid in intravacuolar targeting of the drug cargo as observed by confocal microscopy studies. We also observed that a lower dose of antibiotic was sufficient to clear the pathogen from mice and increase their survivability using the L-MSN oral delivery system.

Chitosan derived from chitin is one of the most abundant naturally occurring biocompatible polymers obtained from fungi and arthropods. In this work, we report the enhancement in the bactericidal efficacy of CHI in the presence of a sharp nanotopography. High-aspect ratio nanostructured surface (NSS) was fabricated using a single-step deep reactive ion etching technique (DRIE). Post fabrication, CHI coating was carried out using a layer-by-layer (LBL) dip coating process on the flat and nanostructured surfaces. Antibacterial efficacy of the flat silicon surface coated with CHI (Si_CHI) and NSS coated with CHI (NSS_CHI) was tested against both Gram-negative (G-ve) bacteria E. coli and Gram-positive (G+ve) bacteria S. aureus. NSS_CHI exhibited superior antibacterial property against G-ve and G+ve microbes as compared with Si_CHI and NSS substrates. Scanning electron microscopy (SEM) and fluorescence microscopy were used to study the morphology and viability of the bacteria on all the surfaces. Also, biofilm quantification was carried out on all the engineered surfaces for both E. coli and S. aureus using crystal violet (CV) staining. NSS_CHI was found to have the minimum biofilm formation on its surface exhibiting its superior antibacterial property. This study shows that the antibacterial and antibiofilm efficiency of CHI can be augmented by combining it with a sharp nanotopography.

Iron nanoparticles (NPs) of size less than 20 nm were synthesized using an in-house developed cryomill.