Designing Polymer Brushes: Promising platforms for Proteins Antifouling, Mesophilic Enzymes Thermal Stability, and Targeted Drug Delivery

The grafting of polymer chains on flat surfaces or nanoparticles is a promising approach to surface derivatization and manipulation that is increasingly being used in a variety of fields.

Surface-confined polymers can be prepared via two main techniques: the grafting from, which leads to higher surface coverage (number of polymer chains/nm2), and the grafting to, which has the disadvantage of yielding low surface coverage because of steric hindrance increase as the polymer film thickness increases.

Here, we demonstrate the generation of a number of polymer brush-based platforms that have different purposes according to the polymer nature and its functionality. 

First, a robust, highly selective, and efficient method to prepare dense poly (ethylene glycol) (PEG) polymer brushes on silicon substrates by the grafting to method via solvent-free, catalyst-free, strain-promoted acetylene–azide cycloaddition (SPAAC) reaction is developed. The prepared PEG polymer brushes displayed efficient antifouling properties and stability in aqueous media for a period of at least two months.

Next, we demonstrate the development of a cocoon structure formed by a synthetic reactive copolymer that bound to the lysine residues on a wide range of enzymes and improve their thermal stability while maintaining the enzyme activity. The copolymer-enzyme conjugate has further been immobilized on silica nanoparticles to provide easy separation and recyclability. The efficiency of the conjugate has been validated by testing on a model enzyme that showed a high improvement of thermal stability and reusability.

Finally, we demonstrate the development of a dual-stimuli responsive platform for delivering toxic drugs to target areas in a remotely controlled manner. As a proof of concept, a model drug is loaded on a polymer brush-modified surface and was released only upon the application of an external and internal stimulus. When tested against 4T1 tumor cell line, the platform has been shown to significantly halt cells proliferation when the model drug release is triggered.