Mesoporous silica nanoparticle supported lipid bilayers for targeted antibiotic therapeutics

摘要

Introduction: Drug-resistant bacteria are an emerging clinical heath threat, and currently cause millions of serious infections annually in the US alone. Some resistant microbial pathogens with current or potential clinical relevance include Burkholderia pseudomallei, Francisella tularensis, Bacillus anthracis, Yersinia pestis, and MRSA among many others. With Burkholderia pseudomallei (Bp) infections, pneumonic and septic forms of melioidosis can occur with as few as 10 aerosolized bacteria, and result in highly variable incubation periods (years), which require prolonged antibiotic therapy for effective treatment (months). In this work, targeted nanoparticles were used to kill Burkholderia pseudomallei and Burkholderia thailandensis, in vitro and in vivo respectively, by overcoming a natural resistance mechanism of these microbes. Materials and Methods: The nanoparticle drug carrier we developed for treatment of Burkholderia was comprised of mesoporous silica nanoparticles (MSNPs), which are enveloped by a fused lipid bilayer to form a therapeutic nanoparticle system known as a 'protocell. The MSNP component of the system was synthesized using a well-known aerosol generation technique that yields a polydisperse mesoporous nanoparticle population ranging in size between roughly 10-1000 nanometers. Following synthesis, MSNPs are typically calcined to remove organics and fused with lipids to form protocells. Here, MSNPs were first solute-loaded with antibiotics by equilibrium partitioning, and then fused with targeted liposomes to produce a biocompatible therapeutic nanoconstruct. To fully characterize this nanoparticle system, we employed a host of analysis techniques for both the MSNPs and protocells, including dynamic light scattering (DLS), transmission electron microscopy (TEM), scanning mobility particle sizing (SMPS), optical particle sizing (OPS), nanoparticle tracking analysis (NTA), zeta potential analysis (Zeta), and surface area and porosity characterization (ASAP). Results and Discussion: Protocells modified targeting moieties conjugated to the lipid bilayer showed a high degree of specificity to the corresponding targeted cell lines in vitro. Gentamicin-resistant Bp was efficiently killed in vitro using targeted, gentamicin-loaded protocells by overcoming an efflux pumping resistance mechanism. In vivo, protocells modified with peptide 'zipcodes' showed highly specific uptake in targeted lung tissues following IV administration, as confirmed by ICP-MS. Additionally, in vivo studies with targeted, protocell-administered gentamicin against Burkholderia thailandensis resulted in significantly improved survival of rodents as compared to control groups. Figure 1: Effectiveness in vivo of gentamicin-loaded protocells against B. thailandensis. Conclusions: Mesoporous silica nanoparticle supported lipid bilayers (i.e. 'protocells') can be easily loaded with small molecule therapeutics and efficiently targeted to specific cell types and tissues for various drug delivery applications. Furthermore, this drug carrier system has demonstrated, both in vitro and in vivo, to be a highly effective and safe delivery platform to treat antibiotic-resistant bacterial infections, even after the bacteria have evolved resistance against the antibiotic loaded into the protocell nanoconstruct.