Special issue: Biocompatible polymers: fundamentals and applications

Biocompatibility is a primary concept in the development of biomaterials. Its definition has evolved over the years in parallel with advances in the field. Biomaterials research initially focused on the development of long-term implantable medical devices, and the term “biocompatible” began to be used in the 1970s [1]. At that time, “biocompatible” referred to non-toxic, non-immunogenic, non-thrombogenic, non-carcinogenic, and non-irritant [2]. Subsequently, biomaterials research expanded beyond long-term implantable devices to include biodegradable implants and tissue engineering scaffolds. In 1987, biocompatibility was defined as “the ability of a material to perform with an appropriate host response in a specific application” [3].

With the remarkable progress of the field, biomaterials have come to be used not only for the delivery of drugs, genes, and engineering cells, but also in biotechnology, where specific interactions between biomaterials and cells are essential. Accordingly, biocompatibility was redefined in 2008 as follows: “Biocompatibility refers to the ability of a biomaterial to perform its desired function with respect to a medical therapy, without eliciting any undesirable local or systemic effects in the recipient or beneficiary of that therapy, but generating the most appropriate beneficial cellular or tissue response in that specific situation, and optimizing the clinically relevant performance of that therapy [2].” More recently, the concept has further expanded to include the customization of interactions at the material–tissue interface for each specific application [4].

Biocompatible polymers constitute one of the major research areas in biomaterials science. Key material characteristics that influence host responses include material composition; micro- or nano-structure and morphology; crystallinity and crystallography; elastic modulus; water content and hydrophobic–hydrophilic balance; macro-, micro-, and nano-porosity; surface chemical composition, chemical gradients, and molecular mobility; surface topography and surface energy; surface electrical and electronic properties; degradation profiles, degradation products, and their toxicity; leachables, additives, catalysts, contaminants, and their toxicity; and wear debris release profiles [2]. When materials are placed in or on tissues or are in contact with bioactive molecules, various time-dependent biological responses may occur, including protein adsorption and desorption characteristics, cytotoxic effects, immune responses, tissue- or organ-specific cellular responses, platelet adhesion, and tumor formation [2]. These biological reactions should be regulated by tuning polymer characteristics according to the intended application.

In this special issue, we focus on biocompatible polymers, encompassing both synthetic and natural polymers, for a wide range of applications. Among them, biodegradable and antifouling polymers are particularly important for sustainable development, which represents a critical global challenge [5]. In recent years, Polymer Journal has published at least one special issue annually [5,6,7]. Although Polymer Journal has published several special issues related to biocompatible polymers, for example peptide materials [8], biorelated materials [9], and biofunctional gels [10], and carbohydrate polymers [11], we believe that the time has come to comprehensively reconsider the field of biocompatible polymers.

To this end, we organized an editorial team consisting of the editor-in-chief, an associate editor, and guest editors. This special issue comprises 10 Original Articles, 4 Focus Reviews, and 1 Review contributed by outstanding researchers, covering a broad range of topics related to biocompatible polymers such as antifouling polymers, drug and gene delivery systems, and protein separation. We believe that this issue will be of significant value to the readers of Polymer Journal. Finally, we sincerely thank all authors and referees for their valuable contributions.