Imaging and Targeted Antibacterial Therapy Using Chimeric Antimicrobial Peptide Micelles.

Infectious diseases induced by multidrug-resistant bacteria are a challenging problem in medicine because of global rise in the drug resistance to pathogenic bacteria. Despite great efforts on the development of antibiotics and antimicrobial agents, there is still a great need to develop a strategy to early detect bacterial infections and eradicate bacteria effectively and simultaneously. The innate immune systems of various organisms produce antimicrobial peptides, which kill a broad range of bacteria with minimal cytotoxicity to mammalian cells. Therefore, antimicrobial peptides have recently attracted increasing attention as an alternative to conventional antibiotics in antibacterial medications. Here, we report a new family of antibacterial agents, which is formulated from self-assembly of a chimeric antimicrobial lipopeptide (DSPE-HnMc) and amphiphilic biodegradable polymers. HnMc micelles could effectively bind the bacterial membrane to kill a wide spectrum of bacteria and bacterial biofilms. In the studies of mouse models of drug-resistant bacterial infections, HnMc micelles could target bacterial infections with high specificity and also kill drug-resistant bacteria effectively, demonstrating the great potential of HnMc micelles as imaging and targeted antibacterial agents. These findings also provide new insight into the design of antimicrobial peptide-based nanomedicine for detection and treatment of bacterial infections.

Thrombus targeting aspirin particles for near infrared imaging and on-demand therapy of thrombotic vascular diseases.

A blood clot (thrombus) is formed as a final product of the hemostatic process with two major components, a mesh of cross-linked fibrin and platelets activated by high concentration of hydrogen peroxide (H2O2). Thrombus formation impedes blood flow to brain and heart and is a principle cause of life-threatening diseases such as stroke and myocardial infarction. Aspirin has been widely used for the treatment and prevention of various cardiovascular diseases, but is unable to target a thrombus and scavenge a high level of H2O2. In this study, we report thrombus targeting aspirin polyconjugate particles (T-APP) as a near infrared imaging agent and on-demand therapeutic agent for thrombotic vascular diseases. T-APP were formulated from H2O2-activatable aspirin polyconjugate, fibrin-specific peptides and fluorescent IR780. In mouse models of tail bleeding and arterial thrombosis, T-APP targeted the thrombosed vessels rapidly with excellent specificity. T-APP also exerted highly strong antithrombotic activity in the thrombosed vessel by suppressing anti-inflammatory cytokines and inhibiting platelet activation. Based on the unique features such as specific thrombus targeting, H2O2 scavenging, and on-demand therapeutic actions, the rationally engineered T-APP have important ramifications on imaging and on-demand therapy of thrombotic disorders.

Acid-triggered echogenic nanoparticles for contrast-enhanced ultrasound imaging and therapy of acute liver failure.

There has been increasing interest in the development of pathological stimulus-activatable nanoplatforms with theranostic functions. Here, we report ketalized maltodextrin (KMD) nanoparticles which are able to deliver therapeutic and imaging functions to the acidic conditions simultaneously, as may be found in the site of inflammation. KMD was synthesized as a platform of the theranostic nanoparticles by conjugating acid-cleavable hydrophobic moieties to maltodextrin through carbonate bonds. KMD nanoparticles could undergo acid-triggered hydrolytic degradation to generate carbon dioxide (CO2) bubbles, amplifying the ultrasound signal. The potential of KMD nanoparticles as a drug carrier was evaluated using silymarin as a model drug. KMD nanoparticles displayed significantly enhanced ultrasound contrast at acidic pH and released drug payloads in acid-triggered manners. The translational potential of silymarin-loaded KMD (s-KMD) nanoparticles as ultrasound contrast agents and therapeutic agents was thoroughly evaluated using cell culture models and mouse models of acetaminophen (APAP)-induced acute liver failure. s-KMD nanoparticles exhibited significantly enhanced ultrasound contrast in the APAP-intoxicated liver and also remarkably suppressed the hepatic damages by inhibiting the expression of pro-inflammatory cytokines. These results suggest that KMD nanoparticles hold tremendous potential as theranostic agents for various inflammatory diseases.