Temperature-Responsive Polymer Brush Coatings for Advanced Biomedical Applications

Abstract

Modern biomedical technologies predict the application of materials and devices that not only can comply effectively with specific requirements, but also enable remote control of their functions. One of the most prospective materials for these advanced biomedical applications are materials based on temperature-responsive polymer brush coatings (TRPBCs). In this review, methods for the fabrication and characterization of TRPBCs are summarized, and possibilities for their application, as well as the advantages and disadvantages of the TRPBCs, are presented in detail. Special attention is paid to the mechanisms of thermo-responsibility of the TRPBCs. Applications of TRPBCs for temperature-switchable bacteria killing, temperature-controlled protein adsorption, cell culture, and temperature-controlled adhesion/detachment of cells and tissues are considered. The specific criteria required for the desired biomedical applications of TRPBCs are presented and discussed.

Keywords: biomedical applications; brushes; coatings; temperature-responsive polymers.

Figure 1

Advanced biomedical applications of the TRPBCs and the specific criteria required for these applications.

Figure 2

Schematic view of the transition of the TRPBCs from the extended hydrophilic chain to the collapsed hydrophobic globule caused by LCST (a) and the transition from the hard glassy state to the soft rubbery state (Tg) (b).

Figure 3

The simplified mechanisms of the LCST or UCST transitions for NIPAM (a), OEGMA (b) and NAGA (c) based TRPBCs.

Figure 4

Functionalization of surfaces (a), subsequent grafting of a multifunctional initiator for a controlled living surface-initiated polymerization (b), polymerization of a reactive monomer, initiated by reactive groups of the multifunctional initiator (c), and the resulting grafted polymer brushes (d).

Figure 5

Typical multifunctional initiators for SI-ATRP.

Figure 6

The most common multifunctional initiators for SI-RAFT.

Figure 7

The most common multifunctional initiators for SI-PP or SI-AP.

Figure 8

Chemical structures of TRPBCs for advanced biomedical applications. N-isopropylacrylamide (a), oligo(ethylene glycol)ethyl ether methacrylate with Mw = 246 (OEGMA246) (b), di(ethylene glycol)methyl ether methacrylate (c), N,N-dimethylaminoethyl methacrylate (d) and their copolymers with units from other functional monomers (e–h) poly(N-acryloyl glycinamide-co-N-phenylacrylamide) (i), poly(imidazoled glycidyl methacrylate-co-diethylene glycol methyl ether methacrylate) (j), poly(butyl methacrylate) (k) and poly(cholesteryl methacrylate) (l).

Figure 9

Controllable bacterial kill–release strategy based on TRPBCs.

Figure 10

Adhesion and detachment profiles of human bone marrow mesenchymal stem cells (hbmMSC) and other human bone marrow-derived cells on poly(NIPAM-co-N,N-dimethylaminopropylacrylamide-co-N-tert-butylacrylamide) TRPBCs (A) and the mechanism of the separation of hbmMSC cells from other human bone marrow-derived cells (see text) (B) (with permission from [139]).

Figure 11

Interactions of TRPBCs with cells at T > LCST and T < LCST (a). The detachment of the cell sheet from the TRPBCs (b).

Figure 12

Temperature-controlled three-stage switching of wetting (a), morphology (b), and BSA absorption (c), determined for copolymer poly(4-vinylpyridine-co-OEGMA246) TRPBCs. Representative micrographs recorded with AFM (b) and fluorescence microscopy (for BSA molecules) labeled with Alexa Fluor (c) (with permission from [154]).

Figure 13

Orientation of the BSA and IgG proteins adsorbed to PBMA-based TRPC at a temperature below (a,c) and above (b,d) its glass transition (Tg). The different domains of BSA (red—Albumin 1, blue—Albumin 2, and green—Albumin 3) and IgG (red—Fab, blue—Fc) are distinguished by colors (modified with permission from [25]).