Organic polymer coatings have been commonly used in biomedical field, which play an important role in achieving biological antifouling, drug delivery, and bacteriostasis. With the continuous development of polymer science, organic polymer coatings can be designed with complex and advanced functions, which is conducive to the construction of biomedical materials with different performances. According to different physical and chemical properties of materials, biomedical organic polymer coating materials are classified into zwitterionic polymers, non-ionic polymers, and biomacromolecules. The strategies of combining coatings with substrates include physical adsorption, chemical grafting, and self-adhesion. Though the coating materials and construction methods are different, many biomedical polymer coatings have been developed to achieve excellent performances, i.e., enhanced lubrication, anti-inflammation, antifouling, antibacterial, drug release, anti-encrustation, anti-thrombosis, etc. Consequently, a large number of biomedical polymer coatings have been used in artificial lungs, ureteral stent, vascular flow diverter, and artificial joints. In this review, we summarize different types, properties, construction methods, biological functions, and clinical applications of biomedical organic polymer coatings, and prospect future direction for development of organic polymer coatings in biomedical field. It is anticipated that this review can be useful for the design and synthesis of functional organic polymer coatings with various biomedical purposes.

Surface functionalization with lubrication and antimicrobial properties can significantly enhance the therapeutic efficacy and minimize the infection risk in implanted medical devices, yet an effective combination of these features with a convenient preparation method remains a great challenge. Inspired by the self-adhesive capability of mussel, the superlubricity of articular cartilage, and the antimicrobial performance of coumarin derivative, in this study we developed a self-adhesive copolymer, PDAM, integrating both lubrication and antimicrobial functionalities. Using dopamine methacrylamide, 2-methacryloyloxyethyl phosphorylcholine, and 7-acryloyloxy-4-methylcoumarin as raw materials, the copolymer was successfully synthesized by free radical polymerization, which could be easily applied to the Ti substrates via a dipping method, forming a stable coating with enhanced lubrication and antimicrobial properties. The characterizations of X-ray photoelectron spectroscopy and fluorescence microscopy verified the desired self-adhesion and durability. The lubrication behavior was investigated via microscopic and macroscopic friction experiments utilizing atomic force microscopy and universal mechanical tester under various test conditions. Additionally, the antimicrobial property, a synergy of phosphorylcholine-induced hydration effect and antibacterial performance of coumarin derivative, was validated by extensive in vitro bacterial tests. In summary, the PDAM copolymer coating, much simple in its preparation and surface modification process, achieved excellent antimicrobial properties by bacteriostatic and anti-adhesion mechanisms, offering a promising potential for surface functionalization of implanted medical devices.

The anticoagulation and hemostatic properties of blood-contacting materials are opposite lines of research, but their realization mechanisms are inspired by each other. Contact between blood and implantable biomaterials is a classic problem in tribological research, as both antithrombotic and hemostatic materials are closely associated with this problem. Thrombus formation on the surfaces of blood-contacting biomedical devices can detrimentally affect their performance and patient life, so specific surface functionalization is required. Currently, intensive research has focused on the development of super-lubricated or super-hydrophobic coatings, as well as coatings that deliver antithrombotic drugs. In addition, hemostatic biomaterials with porous structures, biochemical substances, and strongly adhesive hydrogels can be used to achieve rapid and effective hemostasis via physical or biochemical mechanisms. This article reviews methods of preparing anticoagulant coatings on material surfaces and the current status of rapid hemostatic materials. It also summarizes fundamental concepts for the design and synthesis of anticoagulant and hemostatic materials by discussing thrombosis and hemostasis mechanisms in biomedical devices and normal organisms. Because there are relatively few reports reviewing the progress in surface-functionalized design for anticoagulation and hemostasis, it is anticipated that this review can provide a useful summary of the applications of both bio-adhesion and bio-lubrication techniques in the field of biomedical engineering.

Osteoarthritis is associated with the significantly increased friction of the joint, which results in progressive and irreversible damage to the articular cartilage. A synergistic therapy integrating lubrication enhancement and drug delivery is recently proposed for the treatment of early-stage osteoarthritis. In the present study, bioinspired by the self-adhesion performance of mussels and super-lubrication property of articular cartilages, a biomimetic self-adhesive dopamine methacrylamide–poly(2-methacryloyloxyethyl phosphorylcholine) (DMA–MPC) copolymer was designed and synthesized via free radical polymerization. The copolymer was successfully modified onto the surface of biodegradable mesoporous silica nanoparticles (bMSNs) by the dip-coating method to prepare the dual-functional nanoparticles (bMSNs@DMA–MPC), which were evaluated using a series of surface characterizations including the transmission electron microscope (TEM), Fourier transform infrared (FTIR) spectrum, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), etc. The tribological test and in vitro drug release test demonstrated that the developed nanoparticles were endowed with improved lubrication performance and achieved the sustained release of an anti-inflammatory drug, i.e., diclofenac sodium (DS). In addition, the in vitro biodegradation test showed that the nanoparticles were almost completely biodegraded within 10 d. Furthermore, the dual-functional nanoparticles were biocompatible and effectively reduced the expression levels of two inflammation factors such as interleukin-1β (IL-1β) and interleukin-6 (IL-6). In summary, the surface functionalized nanoparticles with improved lubrication and local drug release can be applied as a potential intra-articularly injected biolubricant for synergistic treatment of early-stage osteoarthritis.

The occurrence of osteoarthritis is closely related to progressive and irreversible destruction of the articular cartilage, which increases the friction significantly and causes further inflammation of the joint. Thus, a scaffold for articular cartilage defects should be developed via lubrication restoration and drug intervention. In this study, we successfully synthesized gelatin-based composite hydrogels, namely GelMA-PAM-PMPC, with the properties of biomimetic lubrication and sustained drug release by photopolymerization of methacrylic anhydride modified gelatin (GelMA), acrylamide (AM), and 2-methacryloyloxyethyl phosphorylcholine (MPC). Tribological test showed that the composite hydrogels remarkably enhanced lubrication due to the hydration lubrication mechanism, where a tenacious hydration shell was formed around the zwitterionic phosphocholine headgroups. In addition, drug release test indicated that the composite hydrogels efficiently encapsulated an anti-inflammatory drug (diclofenac sodium) and achieved sustained release. Furthermore, the in vitro test revealed that the composite hydrogels were biocompatible, and the mRNA expression of both anabolic and catabolic genes of the articular cartilage was suitably regulated. This indicated that the composite hydrogels could effectively protect chondrocytes from inflammatory cytokine-induced degeneration. In summary, the composite hydrogels that provide biomimetic hydration lubrication and sustained local drug release represent a promising scaffold for cartilage defects in the treatment of osteoarthritis.

Osteoarthritis is characterized by lubrication failure of the articular cartilage and severe inflammation of the joint capsule. Lubricating mesoporous silica nanoparticles (MSNs) have been developed for the treatment of osteoarthritis based on enhanced lubrication and local drug delivery. However, MSNs are difficult to degrade in vivo in a short time, resulting in potential toxic effect due to bioaccumulation. In this study, biodegradable MSNs (bMSNs) were prepared through an oil-water biphase stratification method, and modified with poly(2-methacryloyloxyethyl phosphocholine) (PMPC) to synthesize lubricating drug-loaded nanoparticles (bMSNs-NH₂@PMPC) by photopolymerization. The in vitro degradation test demonstrated that the bMSNs and bMSNs-NH₂@PMPC almost degraded within 7 days. The tribiological test showed that the lubrication property of the bMSNs-NH₂@PMPC was greatly improved, with a reduction of 50% in the friction coefficient (COF) compared with the bMSNs. It was attributed to hydration lubrication mechanism by which a tenacious hydration layer is formed surrounding the zwitterionic headgroups (N⁺(CH₃)₃ and PO₄^- ) in PMPC polyelectrolyte polymer. Additionally, the bMSNs-NH₂@PMPC maintained excellent lubrication property under degradation and achieved sustained drug release behavior compared with the bMSNs. In summary, the biodegradable bMSNs-NH₂@PMPC developed in this study with the properties of enhanced lubrication and drug delivery may be a promising approach for osteoarthritis therapy.