Biological Effects, Applications and Design Strategies of Medical Polyurethanes Modified by Nanomaterials

Abstract

Polyurethane (PU) has wide application and popularity as medical apparatus due to its unique structural properties relationship. However, there are still some problems with medical PUs, such as a lack of functionality, insufficient long-term implantation safety, undesired stability, etc. With the rapid development of nanotechnology, the nanomodification of medical PU provides new solutions to these clinical problems. The introduction of nanomaterials could optimize the biocompatibility, antibacterial effect, mechanical strength, and degradation of PUs via blending or surface modification, therefore expanding the application range of medical PUs. This review summarizes the current applications of nano-modified medical PUs in diverse fields. Furthermore, the underlying mechanisms in efficiency optimization are analyzed in terms of the enhanced biological and mechanical properties critical for medical use. We also conclude the preparation schemes and related parameters of nano-modified medical PUs, with discussions about the limitations and prospects. This review indicates the current status of nano-modified medical PUs and contributes to inspiring novel and appropriate designing of PUs for desired clinical requirements.

Keywords: medical application; modification; nanomaterial; polyurethane.

Graphical abstract

Figure 1

Synthesis (A) and structure (B) of a typical polyurethane, and microphase separation morphology (C).

Figure 2

Main applications of polyurethane in biomedical fields. The biomedical applications referring to heart stent, bone scaffold, wound dressing, muscle or nerve repair pattern, drug delivery system, and other products are shown as examples.

Figure 3

Mechanism of action of a NMs/PU drug delivery system on pathological tissue. (A) Drug-loaded NMs/PU reaches the target tissue. (B) NMs degrade the PU to promote the release of the loaded drugs for the killing of pathological cells under an in-vitro stimulus such as magnetic field, light, or pH.

Figure 4

Schematic illustrations of the biocompatibility of PU nanocomposites. (A) NMs induce osteogenesis for the regeneration of hard tissue. (B) NMs promote wound healing by increasing oxygen transmission and excreting metabolites. (C) Conductive NM/PU fibers provide an electrophysiological environment and induce directed migration to accelerate peripheral nerve repair. (D) PU nanocomposites promote surface endothelialization by releasing bioactive NMs.

Figure 5

Antibacterial mechanism of nano-modified PU. (A) The anti-adhesion effect of hydrophobic surfaces. (B) Sterilization of bacterial biofilm via the photothermal effect. (C) NMs released into the surroundings to kill bacteria via oxidized stress damage.

Figure 6

Schematic illustrations of the shape memory of a GO/PU nanocomposite. PU chains are fractured by scratching, but GO recombines the chain segments for initial shape recovery through the photothermal effect under NIR laser irradiation.

Figure 7

Enhanced and new properties of PU nanocomposites provided by commonly used metal, metal oxide, nonmetallic, and organic NMs.

Figure 8

Schematic representations of PU modification with NMs. (A) Physical surface modification (self-assembly) via electrostatic attraction and chemical modification via surface grafting. (B) Blending modification in which the PU and NMs [dispersed by N,N-dimethylformamide (DMF)] are mixed to form PU nanocomposites.

Figure 9

Main clinical applications of biomedical PU nanocomposites.

Figure 10

Nano-modified PU design strategy. The choice of appropriate fabrication processes, NM morphology and components, and weakening NM agglomeration and toxicity are essential.