Advanced dextran based nanogels for fighting Staphylococcus aureus infections by sustained zinc release

The growth in numbers and severity of hospital acquired infections has increased the need to target bacteria locally and specifically. Consequently, smart drug-delivery systems are being developed for local bactericidal action. The approach takes the concept of nanogels in drug delivery of small molecules to the next level by enclosing them in a shell. Versatile polysaccharide nanogels were loaded with zinc ions as antibacterial agents in a miniemulsion process, in order to target methicillin resistant strains of Staphylococcus aureus (MRSA). The encapsulation of drugs in nanogels is limited by the crosslinking density of the gel and the size of the drug. The characterization of the nanogels with inductively coupled plasma optical emission spectroscopy (ICP-OES) revealed that zinc ions cannot be retained within without an additional 'shell' layer. The nanogels were surrounded by a dextran-polyurethane shell, which can retain substances by reduction of water penetration. A delayed zinc release compared to the nanogels was confirmed by ICP-OES. Bacterial tests revealed an antibacterial effect of the shell enhanced nanogels against S. aureus. The studied nanogel system shows potential in locally addressing bacterial infections. The platform is extremely versatile and can be tailored to application as dextran and Zn(NO₃)₂ can be replaced by other polysaccharides (e.g. hyaluronic acid) and antibacterial agents, respectively.