Preparation of Ligand Brush Nanocapsules for Robust Self-Controlled Antimicrobial Activity with Low Cytotoxicity at Target pH and Humidity

Abstract

This study prepared nanocapsules (NCs) with excellent self-controlled antimicrobial activity at pH 6–7 and humidity 45–100%, conditions in which most bacterial and fungal strains thrive. The nanocapsule substrate (NC@SiO2) was 676 nm in diameter, and the ligand-grafted capsule (NC@SiO2-g-MAA) was 888 nm. The large surface area and outer ligand brush of the NCs induced a rapid, self-controlled antibacterial response in the pH and humidity conditions needed for industrial and medical applications. Ligand-brush NCs containing an anionic antimicrobial drug had a rapid release effect because of the repellent electrostatic force and swelling properties of the ligand brushes. Controlled release of the drug was achieved at pH 6 and humidity of 45% and 100%. As many carboxylic acid groups are deprotonated into carboxylic acids at pH 5, the NC@SiO2-g-MAA had a high negative charge density. Carboxylic acid groups are anionized (–COO−) at pH 6 and above and push each other out of the capsule, expanding the outer shell as in a polymer brush to create the release behavior. The surface potential of the NC intermediate (NC@SiO2-MPS) was −23.45 [mV], and the potential of the capsule surface decreased to −36.4 [mV] when the MAA ligand brushes were grafted onto the surface of the capsule intermediate. In an antimicrobial experiment using Escherichia coli, a clear zone of 13–20 mm formed at pH 6, and the E. coli was eradicated completely at pH 6 and pH 7 when the humidity was 100%.

Stimuli-Responsive Triblock Terpolymer Conversion into Multi-Stimuli-Responsive Micelles with Dynamic Covalent Bonds for Drug Delivery through a Quick and Controllable Post-Polymerization Reaction

“…Accordingly, modulating such properties allows for tailoring nanoparticles for specific purposes. The shape of the nanoparticles can be tailored by changing the order, length and solubility of their blocks [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ], while their specificity and responsiveness to drug delivery can be enhanced by modulating the sensitivity to the external stimuli of its stimuli-responsive blocks and by introducing functional groups into the polymeric structure. Therefore, nanocarriers prepared from triblock terpolymers connecting blocks of various targeted specificity and responsiveness are highly promising as drug delivery systems [ 8 , 9 , 10 , 11 , 12 , 13 ].…”

Editorial on Special Issue “Pharmaceutical Formulations with Antimicrobial Properties”

“…In this Special Issue, original papers have been published that bring new perspectives in the development of novel pharmaceutical formulations for antimicrobial applications. Active principles with antimicrobial properties, such as antibiotics [ 1 , 2 , 3 , 4 , 5 ], antifungals [ 6 , 7 ], nutraceuticals [ 8 ], silver or ZnO nanoparticles [ 9 , 10 ], plant materials [ 11 , 12 ] and biocides [ 13 ], have been used to obtain mainly controlled drug delivery systems.…”

“…The last paper of the issue concerns the preparation of ligand brush nanocapsules, based on poly(vinyl pyrrolidone), coated with SiO 2 and grafted with poly(methalic acid sodium salt) [ 13 ]. The ligand-grafted nanocapsule diameter was 888 nm, and they manifested a self-controlled antibacterial response in the pH and humidity conditions needed for medical applications.…”