Bacterial resistance to antibiotics has made it necessary to resort to antibiotics that have considerable toxicities. Here, we show that the cyclic 9-amino acid peptide CARGGLKSC (CARG), identified via phage display on Staphylococcus aureus (S. aureus) bacteria and through in vivo screening in mice with S. aureus-induced lung infections, increases the antibacterial activity of CARG-conjugated vancomycin-loaded nanoparticles in S. aureus-infected tissues and reduces the needed overall systemic dose, minimizing side effects. CARG binds specifically to S. aureus bacteria but not Pseudomonas bacteria in vitro, selectively accumulates in S. aureus-infected lungs and skin of mice but not in non-infected tissue and Pseudomonas-infected tissue, and significantly enhances the accumulation of intravenously injected vancomycin-loaded porous silicon nanoparticles bearing the peptide in S. aureus-infected mouse lung tissue. The targeted nanoparticles more effectively suppress staphylococcal infections in vivo relative to equivalent doses of untargeted vancomycin nanoparticles or of free vancomycin. The therapeutic delivery of antibiotic-carrying nanoparticles bearing peptides targeting infected tissue may help combat difficult-to-treat infections.

A single-step procedure to simultaneously load and protect high concentrations of siRNA in porous silicon nanoparticles (pSiNPs) is presented. Treatment of pSiNPs with an aqueous solution containing siRNA and calcium chloride generates core-shell nanostructures consisting of an siRNA-loaded pSiNP core infiltrated with an insoluble shell of calcium silicate (Ca-pSiNPs). The source of silicate in the shell derives from local dissolution of the pSi matrix, and in solutions containing high concentrations of calcium (II) ion, Ca2SiO4 formation occurs primarily at the nanoparticle surface and is self-limiting. The insoluble calcium silicate shell slows the degradation of the pSiNP skeleton and prolongs delivery of the siRNA payload, resulting in more effective gene knockdown in vitro. Formation of the calcium silicate shell results in an increase in the external quantum yield of photoluminescence from the porous silicon core from 0.1 to 21 %, presumably due to the electronically passivating nature of the silicate shell. Attachment of two functional peptides that incorporate a sequence derived from the rabies virus glycoprotein (RVG) as a neuronal targeting peptide and myristoylated transportan (mTP) as a cell penetrating moiety to the Ca-pSiNPs yields a construct that shows improved gene silencing in vitro and improved delivery in vivo.

Novel hollow silica nanoparticles (HSNPs) for drug delivery vehicles were synthesized using silica-coated magnetic assemblies, which are composed of a number of Fe(3)O(4) nanocrystals, as templates. The core cavity was obtained by removal of Fe(3)O(4) phase with hydrochloric acid and subsequent calcination at a high temperature. HSNPs were modified by amine in order to introduce positive surface charge and further PEGylated for increased solubility in aqueous medium. Doxorubicin as a model drug was loaded into the HSNPs, and notable sustained drug release from HSNPs was demonstrated.

The incidence of adverse effects and pathogen resistance encountered with small molecule antibiotics is increasing. As such, there is mounting focus on immunogene therapy to augment the immune system’s response to infection and accelerate healing. A major obstacle to in vivo gene delivery is that the primary uptake pathway, cellular endocytosis, results in extracellular excretion and lysosomal degradation of genetic material. Here we show a nanosystem that bypasses endocytosis and achieves potent gene knockdown efficacy. Porous silicon nanoparticles containing an outer sheath of homing peptides and fusogenic liposome selectively target macrophages and directly introduce an oligonucleotide payload into the cytosol. Highly effective knockdown of the proinflammatory macrophage marker IRF5 enhances the clearance capability of macrophages and improves survival in a mouse model of Staphyloccocus aureus pneumonia.