The global prevalence of diabetes and its complications have a growing impact individuals worldwide, bringing a non-negligible burden to the lives of patients and social medical systems [1]. In recent years, it has been reported that 9.5 % of the world's population is affected by diabetes, with an ongoing increase [2]. Long-standing diabetes mainly influences cellular and molecular changes, and ultimately damages small and large blood vessels, resulting in a range of complications such as diabetic neuropathy, diabetic retinopathy, and diabetic wounds. Diabetic wounds usually destroy the normal skin regeneration function, leading to the inability of wound healing through the normal physiological pathway [3] (Fig. 1). The main reasons for the difficulty in diabetic wound healing are as follows: (1) The cause of diabetes is mainly due to the obstruction of insulin secretion and function, which leads to the reduction in the body's glucose metabolism and inability to generate and transform many functional proteins. The healing of the wound normally requires the formation of granulation tissue to collagen fibers, so the wound cannot heal for a long time [4]. (2) After many diabetic wounds are infected, the high blood glucose concentration in the body will promote bacterial colonization and biofilm formation, leading to uncontrollable inflammation [5]. In addition, biofilms exist in most ulcers, worsening the overall wound environment [6]. (3) Persistent inflammation caused by excessive reactive oxygen species (ROS) production is also an important reason. ROS are produced by cells, such as damaged inflammatory cells, epithelial cells, and endothelial cells (ECs) [7]. Persistent hyperglycemia in diabetic wounds produces advanced glycation end products (AGEs) in the blood, which directly induce overproduction of ROS. In addition to causing chronic inflammation, excessive ROS can also damage angiogenesis, promote cell senescence, and hinder re-epithelialization [[8], [9], [10]]. (4) Vascular injury makes it difficult to transport oxygen and nutrients to the wound site. These wounds usually occur in the limbs, especially the feet, so diabetic foot is also the most difficult wound healing problem faced by clinicians [11]. The 5-year survival rate after the emergence of new diabetic foot ulcers (DFUs) is only 50–60 %, so it is worse than many common cancers [12]. The latest data from the UK estimates that the total annual management cost of the DFUs is more than 1 billion pounds ($ 1.32 billion), almost 1 % of the total budget of the National Health Service [13]. Peripheral neuropathy is a major complication of diabetes, which can lead to the loss of distal protection of the lower extremities and foot deformation. Wound formation is induced under the influence of other mechanical injuries such as shoes incompatibility [14]. Combined with the many reasons why diabetic wounds are difficult to heal, lower body amputation has become an unavoidable result. In the current clinical treatment guidelines, conventional drug therapy and metabolic surgery combined with biomaterial dressings are the best treatment [15,16].

Traditional dressings, such as cotton composite dressings woven with gauze or merely gauze, provide wound protection from bacterial contamination and allow normal exchange of gas. However, on account of frequent replacement needs, secondary damage and inconvenience caused by dressing removal have led to the gradual elimination of traditional dressings for chronic wound healing. In the past ten years, new cell therapy has been more effective in the treatment of wounds. Individualized treatment of different types of chronic wounds can be achieved by encapsulating antibacterial molecules, immunomodulatory cytokines, growth factors, miRNA or exosomes in new dressings [17]. Therefore, drug delivery materials and drug delivery methods are now carefully considered by researchers [18,19]. Transdermal administration has many advantages, including improving patient compliance, sustained release, avoiding gastric irritation, and eliminating first-pass effects. Compared with transdermal administration, subcutaneous injection is likely to induce hypersensitivity and bleeding at the site of administration in clinical practice, which has certain limitations [20]. The low compliance and side effects of patients with fear acupuncture affect the overall therapeutic effect of drugs [[21], [22], [23]]. Fortunately, due to the development of micro-modification method in the past few decades, microneedles (MNs) technology has greatly improved the above treatment drawbacks [24]. MNs are hundreds of micron-sized thorn-like substances made of better biocompatible materials. In recent years, many studies have been based on MNs to achieve drug delivery. Researchers are also trying to go beyond the theory and apply MN technology to clinical practice [20,25]. According to Junying Zhang et al., the number of different types of MNs currently undergoing clinical trials was counted. Microneedle patches (MNPs) ranked second with 41 (32 %), relatively high and promising (Fig. 2). Compared with other types of MNs, we believe that the patch form can cover irregular diabetic wounds better than microinjection [25]. The former has a substrate that can also absorb the wound exudate. In addition, the MNP can ensure the delivery of drugs and avoid incomplete spraying of drugs in the later stage of needle rolling. The design of the MNP focuses on the arrangement of the array and the parameters of the acupuncture (height, base diameter, needle distance, angle), which effectively affect the drug load and the adhesion ability in the wound. Based on the current research on MNPs for diabetic wounds, dissolved MNPs and hydrogel MNPs dominate. They have attracted great attention from researchers in the field of tissue engineering due to their superior biocompatibility, minimal invasiveness, and prolonged drug retention time [26,27]. From the selection of the substrate to the linkage of the needle carrying the drug, the two parts in the initial study do not affect each other to the recent diverse cascade reactions, and the MNP has a promising future in the treatment of diabetic wounds.

By searching the web of science database with the keywords ‘microneedle ‘and ‘diabetic wound ‘, we found that the first original experimental article was published in August 2020. Yajuan Su et al. hypothesized that dissolving MN arrays containing engineering peptides can overcome the physical barrier of biofilms, so that peptides can better penetrate and destroy them, and proved that MNPs can deliver peptides more effectively than free drugs, which is an effective intervention with great potential [28]. By 2023, a total of 44 original experimental articles have been published with the same keywords, and the number of articles has increased over years. In addition, after searching the major databases, we found that there is no relevant article to discuss the field of MNP in the treatment of diabetic wounds. Therefore, this article will evaluate the therapeutic effect of MNPs on diabetic wounds by combining the drug delivery advantages, needle tip design, and biomolecule drug loading capacity of MNPs. By reading this article, researchers can gain insights into the current encapsulated drugs and their functionalities, which can inspire more innovative design approaches. Additionally, a profound understanding of the pathological challenges associated with MNP treatments for diabetic wounds will help in setting clearer directions for future research.