Multi-functional wound dressings based on silicate bioactive materials

Abstract

Most traditional wound dressings passively offer a protective barrier for the wounds, which lacks the initiative in stimulating tissue regeneration. In addition, cutaneous wound healing is usually accompanied by various complicated conditions, including bacterial infection, skin cancer, and damaged skin appendages, bringing further challenges for wound management in clinic. Therefore, an ideal wound dressing should not only actively stimulate wound healing but also hold multi-functions for solving problems associated with different specific wound conditions. Recent studies have demonstrated that silicate bioceramics and bioglasses are one type of promising materials for the development of wound dressings, as they can actively accelerate wound healing by regulating endothelial cells, dermal fibroblasts, macrophages, and epidermal cells. In particular, silicate-based biomaterials can be further functionalized by specific structural design or doping with functional components, which endow materials with enhanced bioactivities or expanded physicochemical properties such as photothermal, photodynamic, chemodynamic, or imaging properties. The functionalized materials can be used to address wound healing with different demands including but not limited to antibacterial, anticancer, skin appendages regeneration, and wound monitoring. In this review, we summarized the current research on the development of silicate-based multi-functional wound dressings and prospected the development of advanced wound dressings in the future.

Introduction

Dysregulated wound healing causes a series of clinical issues including chronic wounds such as diabetic foot ulcers, venous leg ulcers, or pressure ulcers [1]. Chronic wounds can be triggered by various factors including infection, systemic diseases like diabetes and malignant tumors, local tissue hypoxia, ischemia-reperfusion injury, aging, etc [2,3]. To date, there are various biological, chemical, and physical therapies available for wound management in clinic [4]. Among all current therapies, material-based wound dressing is one of the most commonly used approaches [5]. Indeed, wound dressing is an indispensable element of standard wound care procedures in clinic.

Traditional wound dressings, such as gauze and cotton wool which contain no bioactive components, are usually used to prevent contamination in wound management [6]. However, their protective capacity reduces when the dressing becomes moistened by wound exudate or external fluids [7]. In particular, traditional dressings may not be able to meet some clinic needs as wounds are often associated with complicated conditions such as chronic wounds, infected wounds, and disease-related wounds. For example, bacterial infection will badly affect wound healing and the spread of antibiotic-resistant bacteria significantly increases the difficulty of preventing infection [8]. In addition, surgical removal of the tumor tissue is the standard procedure for treating skin cancer such as melanoma, however, this also causes cutaneous tissue defect as well as a high risk of tumor recurrence [9]. Furthermore, traditional wound dressings are lack of activity to stimulate the regeneration of skin appendages, such as hair follicles, sweat glands, and sebaceous glands. Indeed, skin appendages play essential roles in maintaining the physical, chemical, and biological functions of the skin [10]. Therefore, these demands raise new requirements for wound dressings, putting forward new challenges for biomaterial research.

To address the above issues, more attention has been given to those biomaterials which are bioactive and able to actively stimulate wound healing by regulating functions of healing-related cells. Among all current materials, silicate-based biomaterials have been demonstrated to be one of the most promising materials for the design of wound dressings as they not only possess excellent biocompatibility but also hold various bioactivities such as regulation of the different types of cells involved in the wound healing process. In addition, the multi-functional design of wound dressing materials is important, which not only uses the synergy of multi-functional physicochemical properties and biological activities of materials to further promote wound healing, but also endows materials with other functions such as antibacterial or anti-tumor abilities. Furthermore, the development of wound dressings with monitoring function during healing also holds great significance as wound healing is a dynamic process, and real-time monitoring wound environment enables dynamic intervention during the healing process thereby generating better therapeutic outcomes [11]. For instance, increased pH is often observed before clinically discernible infection in burns, and therefore can be used as an indicator of infection to guide the antibacterial treatment [12]. Given the trends of the bioactive and multi-functional design in the development of wound dressings, this review summarized the current research on the development of wound dressings with the focus on both silicate-based bioactive and multi-function designs including antibacterial, anti-tumor, skin appendage regeneration and wound monitoring (Fig. 1), and prospected the development of advanced wound dressings in the future.