Efficacy and Safety of Intralesional Triamcinolone Versus Combination of Triamcinolone with 5-Fluorouracil in the Treatment of Keloids and Hypertrophic Scars: A Systematic Review and Meta-analysis

Targeting Diverse Wounds and Scars: Recent Innovative Bio-design of Microneedle Patch for Comprehensive Management

Wounds and the subsequent formation of scars constitute a unified and complex phased process. Effective treatment is crucial; however, the diverse therapeutic approaches for different wounds and scars, as well as varying treatment needs at different stages, present significant challenges in selecting appropriate interventions. Microneedle patch (MNP), as a novel minimally invasive transdermal drug delivery system, has the potential for integrated and programmed treatment of various diseases and has shown promising applications in different types of wounds and scars. In this comprehensive review, the latest applications and biotechnological innovations of MNPs in these fields are thoroughly explored, summarizing their powerful abilities to accelerate healing, inhibit scar formation, and manage related symptoms. Moreover, potential applications in various scenarios are discussed. Additionally, the side effects, manufacturing processes, and material selection to explore the clinical translational potential are investigated. This groundwork can provide a theoretical basis and serve as a catalyst for future innovations in the pursuit of favorable therapeutic options for skin tissue regeneration.

Scarring Skin: Mechanisms and Therapies

Skin injury always results in fibrotic, non-functional scars in adults. Although multiple factors are well-known contributors to scar formation, the precise underlying mechanisms remain elusive. This review aims to elucidate the intricacies of the wound healing process, summarize the known factors driving skin cells in wounds toward a scarring fate, and particularly to discuss the impact of fibroblast heterogeneity on scar formation. To the end, we explore potential therapeutic interventions used in the treatment of scarring wounds.

Recurrence rates in the treatment of keloids and hypertrophic scars with intralesional triamcinolone combined with other intralesional agents

Hypertrophic scars (HTS) and keloids are pathologic scars that are products of a wound healing pathway error attributed to genetic and inflammatory causes (Leventhal et al., Arch Facial Plast Surg 8(6):362-368. https://doi.org/10.1001/archfaci.8.6.362 , 2006). Methods of pathologic scar treatment include intralesional agents, cryotherapy, surgical excision, pressure dressings, topical agents, laser resurfacing, radiotherapy, and other investigational therapies (Leventhal et al. 2006). The recurrence of pathologic scar is high across all treatment modalities, including the use of intralesional agents (Trisliana Perdanasari et al., Arch Plast Surg 41(6):620-629. https://doi.org/10.5999/aps.2014.41.6.620 , 2014). In the treatment of pathologic scar, combination approaches using intralesional agents, such as triamcinolone (TAC), 5-fluorouracil (5FU), verapamil (VER), bleomycin (BLM), and botulinum toxin (BTX), are superior therapies when compared to monotherapy (Yosipovitch et al., J Dermatol Treat 12(2):87-90. https://doi.org/10.1080/095466301317085363 , 2001; Yang et al., Front Med 8:691628. https://doi.org/10.3389/fmed.2021.691628 , 2021; Sun et al., Aesthetic Plast Surg 45(2):791-805. https://doi.org/10.1007/s00266-019-01570-8 , 2021). This review assesses recurrence and the reporting of recurrence in pathologic scar after treatment with intralesional triamcinolone (TAC) in combination with another intralesional agent. A literature review was conducted using research journals from PubMed using the following search terms: [(keloid) AND (triamcinolone) AND (combination) AND (intralesional)], as well as [(keloid) AND (triamcinolone) AND (combination)]. Articles were reviewed and included if the article analyzed  or compared intralesional agents for pathologic scar treatment within the last 10 years. The average follow-up period of included articles (n = 14) that utilized combination intralesional therapy (TAC-X) was approximately 11 months (range 1-24 months). Consistent recurrence rate reporting across studies was lacking. The combination agent with the highest recurrence rate was TAC-5FU (23.3%). The range of reported recurrence rates was 7.5-23.3%. Six studies using various intralesional combination regimens reported 0% recurrence over the follow-up period (TAC-5FU, TAC-BTX, TAC-BLM, TAC-CRY). Three studies did not report recurrence rates. While the efficacy of combination therapy is typically assessed via scar scales, the assessment of recurrence across studies of combination therapy is inconsistent and inadequate, with truncated follow-up periods. While scar recurrence can take place during 1-year post-treatment, long-term follow-up (18-24 months) is needed to characterize recurrence in the treatment of pathologic scar using various intralesional agents. Long-term follow-up periods allow patients to receive accurate prognostic information regarding recurrence after combination intralesional therapy. There are limitations to this review in that comparisons were made across studies with varying outcome variables, including scar size, injection concentration and interval, and follow-up period. Standardized follow-up periods and recurrence rate reporting are integral to furthering the understanding of these therapies and enhancing patient care.

Laser Combined with Radiotherapy for Keloid Treatment: A Novel and Efficient Comprehensive Therapy with a Lower Recurrence Rate

BACKGROUND

Keloids are a fibroproliferative skin disorder with a high recurrence rate. Combined therapies are often used in clinical treatment, but, in addition to the relatively high risk of relapse and complexity of the treatment process, side effects remain unknown for combination therapies.

METHODS

A total of 99 patients with keloids in 131 positions were included in this retrospective study. Fractional CO 2 laser therapy was first applied with energy ranging from 360 to 1008 mJ; then, 6-Mev, 900-cGy electron beam irradiation was applied twice. The first pass was initiated within 24 hours after the laser therapy, and the second pass was performed on the seventh day after laser therapy. The Patient and Observer Scar Scale evaluated the lesions before the treatment and at 6, 12, and 18 months after treatment. At each follow-up visit, the patients filled out a questionnaire on recurrence, side effects, and satisfaction.

RESULTS

The authors found a significant decrease in total Patient and Observer Scar Scale score [29 (23, 39) versus 61.2 ± 13.4; P < 0.001] at the 18-month follow-up compared with the baseline value (before the therapy). A total of 12.1% of the patients had recurrences during the 18-month follow-up period (11.1% partial recurrence and 1.0% complete recurrence). The total satisfaction rate was 97.0%. No severe adverse effects were observed during the follow-up period.

CONCLUSIONS

Laser combined with radiotherapy is a new comprehensive therapy comprising ablative lasers and radiotherapy for keloids. It had excellent clinical efficacy, low recurrence rate, and no serious adverse effects.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

3D-printed morphology-customized microneedles: understanding the correlation between their morphologies and the received qualities

Despite remarkable progress in the last decade in transdermal microneedle drug delivery systems, great difficulties in precisely manufacturing microneedles with sophisticated microstructures still strongly retard their practical applications. Herein we propose morphology-customized microneedles (spiral, conical, cylindroid, ring-like, arrow-like and tree-like) fabricated by stereolithography (SLA) based 3D-printing technique, and in-depth investigate the correlation between the customized morphologies and the received qualities of the corresponding microneedles such as the mechanical properties and skin penetration behavior, drug loading capacity and the drug release profiles. Results indicated that 3D-printed morphology-customized microneedles not only enhanced the mechanical strength but also improved both drug loading capacity and drug release behavior, which resulted from their highly controllable and 3D-printable morphologies (surface area and volume). And the in vivo study demonstrated that the 3D-printed morphology-customized microneedles successfully promoted the transdermal delivery of the loaded drug (verapamil hydrochloride) with an enhanced therapeutic efficacy for the treatment of hypertrophic scar.

Comparison of Ultrasound-Assisted Low-Dose Versus Medium-Dose 5-Fluorouracil and Triamcinolone Acetonide in the Treatment of Hypertrophic Scar

Intralesional 5-fluorouracil (5-FU) and triamcinolone acetonide (TAC) injection is effective for the treatment of hypertrophic scar. The side effects of current that recommended 45 mg/ml (high-dose) 5-FU have been reported. However, no previous study has investigated the efficacy and safety of low-dose (2.5 mg/ml) 5-FU with 4 mg/ml TAC or medium-dose (10 mg/ml) 5-FU with 4 mg/ml TAC for treatment of hypertrophic scar. Herein, a retrospective comparative study was conducted. The records of 70 patients, treated with low-dose (2.5 mg/ml) 5-FU and 4 mg/ml TAC every 4 weeks (Group 1) or medium-dose (10 mg/ml) 5-FU and 4 mg/ml TAC every 4 weeks (Group 2), were analyzed. The Vancouver Scar Scale (VSS), vascularity, and thickness of hypertrophic scar at baseline and at 7th-treatment (each group received 6 treatment sessions) were compared. The ultrasound showed the large vascular distribution in scar margins. Both groups gained clinical improvement in VSS, vascularity, and thickness. Group 2 (medium-dose) exhibited significantly better improvement than Group 1 (low-dose). However, the overall side effects rate was 11.4% in Group 1, significantly lower than 31.4% in Group 2. Scar margins were suggested to be target sites for injection. Medium-dose (10 mg/ml) 5-FU + 4 mg/ml TAC could effectively reduce the thickness of hypertrophic scar; however, the side effects rate was also higher in medium-dose group than in low-dose group.

Comparing the Efficacy of Multiple Drugs Injection for the Treatment of Hypertrophic Scars and Keloid: A Network Meta-Analysis

BACKGROUND

There is no consensus regarding the choice of injected drugs for pathological scars. Although the clinical efficacy of different drug treatments was shown in many randomized controlled trials, the efficacies of many drugs are inconsistent. Therefore, this study aimed to determine how different effective drugs are for treating pathological scars. It is anticipated that the study findings may serve as guidelines for plastic surgeons.

METHODS

Relevant literature was extracted from the following databases Cochrane Library, Embase, PubMed, Web of Science, CNKI, Weipu, and Wanfang until June 2022, such as randomized clinical trials (RCTs) evaluating different injected drugs for the treatment of pathological scars, including BTA, TAC, 5-Fu, VER, and BLE.

RESULTS

This network meta-analysis of 1539 patients from 23 articles revealed that the most effective treatment for a pathological scar was TAC + BTA. The effective rate of TAC + BTA combination therapy was significantly different from that of the BTA, TAC, 5-Fu, VER, and BLM monotherapies. TAC+5-FU was more effective than TAC, 5-FU, VER, or BLM alone, and BTA was more effective than both TAC and 5-Fu. The effectiveness of VER and BLM was the same, but both were better than TAC and 5-Fu. No big differences were found between any of the other local injection therapies.

CONCLUSIONS

According to this network meta-analysis, a combination of keloid and hypertrophic scar injection treatment is recommended, especially BTA+TAC. However, this network meta-analysis has some limitations and must be further verified by larger samples and higher quality RCTs.

LEVEL OF EVIDENCE III

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

Complications Following Facial Injection of Growth Factor Solution

OBJECTIVE

Topical injection of growth factor (GF) for facial rejuvenation is unauthorized, but it is commonly performed in China, leading to emerging and challenging complications. The purpose of this study is to investigate the clinical, imaging, and histopathologic characteristics of complications caused by facial GF injection, as well as their treatments and outcomes.

METHODS

We performed a retrospective single-centered case series study on consecutive patients who were treated for complications following facial injection of GF. The primary outcome was the recurrence over follow-up period. The secondary outcomes were the subjective evaluations of the facial aesthetic, symptomatic, and psychological improvements using the Global Aesthetic Improvement Scale (GAIS) and a patient-reported outcome measurement (PROM). Kaplan-Meier analysis and log-rank test were performed to investigate the recurrence.

RESULTS

A total of 32 females with an average age of 42.6 ± 9.4 years were included. Most patients received GF injections in non-medical institutes such as beauty spas and presented with uncontrollable soft tissue hyperplasia, diffuse subcutaneous swelling, and skin redness. Ultrasonography showed heterogeneous hypoechoic or echogenic areas in a thickened and disorganized subcutaneous tissue hierarchy. MRI showed flaky isointensive or hypointensive signals on T1WI and hyperintensive signals on T2WI. 37.5% patient underwent triamcinolone acetonide injection, whereas 62.5% patients underwent surgical interventions. Lipoma-like hyperplastic tissue was found during surgery. HE staining confirmed intramuscular lipoma and fibrolipomatous tissue hyperplasia. Recurrence was found in 37.5% patients over a median follow-up of 6 months. KM curves and log-rank test demonstrated no significant difference in the recurrence between patients who underwent nonsurgical or surgical interventions (p = 0.77). GAIS and PROM scores indicated substantial aesthetic, symptomatic, and psychological improvements in 70%, 91.7%, and 75% patients, respectively.

CONCLUSIONS

Both surgical and nonsurgical interventions are feasible and effective treatment options for GF-induced complications. Although recurrence rate was relatively high, aesthetic, symptomatic, and psychological improvements were achieved in most patients. We developed a workflow that might help diagnose and treat complications following unknown dermal filler injections.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Low-dose intralesional injection of 5-fluorouracil and triamcinolone reduces tissue resident memory T cells in chronic eczema

BACKGROUND

Tissue resident memory T (T_RM) cells have been reported to play a significant role in the pathogenesis and relapse of chronic eczema.

AIM

To compare the efficacy and safety of the intralesional injection of 5-fluorouracil (5-FU) and triamcinolone (TA) with those associated with TA alone for the treatment of chronic eczema.

METHODS

A total of 168 patients were randomized to 5-FU+TA or TA groups and received a one-time intralesional injection of 5-FU+TA or TA only. Biopsies were collected before and 2 wk after treatment for evaluation of histopathological changes. All patients were followed up monthly for up to 1 year.

RESULTS

No serious adverse event was observed in either group. Although the mean atopic dermatitis severity index scores and effective rates were comparable between the two groups after 2 wk of treatment, the relapse rate was significantly lower in the 5-FU+TA group than in the TA group. Histological examination showed significantly fewer CD8⁺ and CD103⁺ T cells but not CD4⁺ T cells in the 5-FU+TA group.

CONCLUSION

One-time intralesional injection of 5-FU+TA is effective and safe for chronic eczema treatment and can further reduce the retention of T_RM cells in the lesional skin and the relapse rate of chronic eczema.

Non-Invasive and Surgical Modalities for Scar Management: A Clinical Algorithm

Scars can lead to aesthetic and functional impairments. The treatment of scars requires meticulous planning and an individually adapted therapeutic strategy. A conceptual algorithm for scar treatment makes everyday clinical work easier for the practitioner and offers more safety for the patient. Based on a retrospective analysis of 1427 patients who presented for treatment of a variety of scars, we developed an algorithm for scar management and treatment. The treatments are presented using case descriptions. Additionally, an electronic search of MEDLINE, EMBASE, and ClinicalTrials.gov databases was performed utilizing combinations of relevant medical subject headings for "scar treatment", "hypertrophic scar treatment" and "keloid treatment". Reference lists of relevant articles and reviews were hand-searched for additional reports. Observed outcomes included: conservative scar therapy, minimally invasive scar therapy, and surgical scar therapy using local, regional and free flaps. With this work, we provide an algorithm for safe scar treatment. For better understanding, we have described a clinical case for each algorithm modality.

Network Meta-Analysis of Different Clinical Commonly Used Drugs for the Treatment of Hypertrophic Scar and Keloid

Background: There is no uniform treatment for pathological scars, including keloids and hypertrophic scars, in clinic currently. Previously, multiple randomized controlled trials have examined the clinical efficacy of different treatments. Nonetheless, the results are inconsistent, and many treatments have not been directly compared. This makes it difficult to conclude which approach is more favorable, in terms of efficacy and safety, for the treatment of pathological scarring. This study aimed at evaluating the efficacy of different injection and topical treatment strategies for hypertrophic scar and keloid.

Methods: Relevant literature from PubMed, Medline, Embase, Scopus, the Cochrane Central Register of Controlled Trials (CCRCT), and WHO International Clinical Trials Registry Platform (WHO-ICTRP) were searched, from database inception through November 2020. Randomized clinical trials evaluating different treatment strategies of pathological scars, including triamcinolone acetonide (TAC), verapamil (VER), 5-fluorouracil (5-FU), botulinum toxin A (BTA), bleomycin (BLM), and silicone gels were included in the study.

Results: The network meta-analysis included a total of 2,009 patients from 29 studies. A network meta-analysis of injection and topical treatment strategies showed that the efficacy of TAC combined with BTA was best in the treatment of pathological scars. Combination therapies of TAC with 5-FU and TAC with BTA significantly improved the clinical efficiency. However, there was no statistically significant difference between other treatment strategies. The order of efficacy predicted by the surface under the cumulative ranking (SUCRA) curve was as follows: TAC+BTA (82.2%) > TAC+5-FU (69.8%) > BTA (67.3%) > 5-FU+silicone (59.4%) > TAC+silicone (58.3%) > 5-FU (49.8%) > BLM (42.0%) > TAC (26.7%) > VER (26.2%) > silicone (18.3%). There was no publication bias revealed based on the funnel diagram.

Conclusion: This study recommends intralesional injection of TAC-BTA and TAC-5-FU combined therapies. But for patients who cannot tolerate the side effects, the use of silicone gels in combination with TAC is recommended. However, these conclusions need to be further confirmed by more randomized controlled trials.

Analysis of the predictors of hypertrophic scarring pain and neuropathic pain after burn

INTRODUCTION

Burn hypertrophic scarring pain is a common and perennial complaint which not only affects patients' quality of life, but also their recovery and reintegration. Physical therapy and medicine regimens are all available for the treatment of hypertrophic scarring pain. Unfortunately, the efficacy of clinical practice is not very satisfactory and the management of hypertrophic scarring pain remains challenging. Therefore, it is of utmost importance to explore the risk factors for hypertrophic scarring pain and further identify whether it is neuropathic pain, aiming to guide the clinical therapy and help patients live a pain-free life.

METHODS

This retrospective study enrolled patients with postburn hypertrophic scarring pain between 2017 and 2020 in a burn center in Shanghai. Research objects were included strictly according to the inclusion criteria and every enrolled patient was included in the study only once. Demographic information, burn and scar characteristics, and pain scores were collected through the Changhai Hospital Medical Information System, patient questionnaire and physician assessment. Using SPSS 26.0 software, the data were first processed by descriptive statistics, and linear and logistic regression analyses were further employed to explore the significant factors.

RESULTS

The sample involving 123 patients was consisted of 56.9% males, 79.7% caused by fire with a median age 40.5 years, total body surface burn-area (TBSA) 44.4%, wound healing time of target scar 57.9 days, hyperplasia time 9.3 months and the scar location mainly in the limbs (55.3%). Of all the included objects, the modified Vancouver Scar Scale (mVSS) total, visual analogue scale (VAS) score, brief pain inventory (BPI) total and the percentage of neuropathic pain were 9.6, 3.3, 36.0 and 74.8%, respectively. Integrating covariates with a P value of <0.10 through preliminary univariate analysis, multivariable linear regression showed sex (P = 0.049), age (P = 0.020), target scar location (P = 0.017, P = 0.254), and pliability (P = 0.016) were linked with severe VAS score; and burn depth of target scar (P = 0.023), hyperplasia time (P = 0.027, P = 0.001), vascularity (P = 0.028), and pliability (P = 0.001) were associated with higher BPI score. Adjusting for potential confounders, hyperplasia time (P = 0.005, P = 0.039) was found to be the only independent risk factor for hypertrophic scarring neuropathic pain in the multivariate logistic regression analysis, with mVSS total of P = 0.062.

CONCLUSIONS

The model in our study has clarified that sex, age, target scar location, burn depth of target scar, hyperplasia time, and vascularity, especially pliability, may provide excellent prediction of hypertrophic scarring pain outcome; for neuropathic pain, only hyperplasia time has further prospects, with mVSS total as a potential forecast. In an era increasingly aware of life quality, this work may contribute to the elaboration of strategies to hypertrophic scarring pain management, provide an individualized therapy, and help patients live a pain-free life.

Botulinum toxin type a intralesional monotherapy for treating human hypertrophic scar in a dose-dependent manner: In an animal model

BACKGROUND

The effect of Botulinum toxin type A (BTX-A) in treating or preventing a hypertrophic scar (HS) had been reported in clinical studies. However, the dose-effect relationship remains unclear.

OBJECTIVE

To study the dose-effect relationship of BTX-A intralesional monotherapy treating human HS.

METHODS

Six HS tissues were collected from six patients. Each tissue was segmented into 24 specimens and split into four groups: negative control (group A), 0.5U BTX-A (group B), 1U BTX-A (group C), and 2U BTX-A (group D). Six nude mice, each was prepared by implanting four specimens (one from each group) into the back for a total of 24 specimens. The process mentioned above were repeated six times. A re-entry operation was performed to obtain the specimens after 8 weeks. The weight of HS, the expression of decorin and TGF-β₁, the proliferation, and migration ability of hypertrophic scar fibroblasts (HSFBs) were compared among groups.

RESULTS

The weight of HS, the expression of decorin and TGF-β₁, the proliferation, and migration ability of HSFBs showed significant differences in groups C and D as compared to group A; there has been no statistical significance in group B.

CONCLUSION

BTX-A showed significant therapeutic efficacy when compared with the negative control group in a dose-dependent manner. BTX-A can reduce the weight of HS, upregulate the expression of decorin, downregulate the expression of TGF-β₁, and inhibit HSFBs proliferation and migration ability. This study indicates that BTX-A intralesional monotherapy treating HS should reach a threshold dose to achieve an effective treatment, and a high dose of BTX-A is more effective than a low dose.

Differential responses to folic acid in an established keloid fibroblast cell line are mediated by JAK1/2 and STAT3

Keloids are a type of disordered scar formation which not only show heterogeneity between individuals and within the scar itself, but also share common features of hyperproliferation, abnormal extra-cellular matrix deposition and degradation, as well as altered expression of the molecular markers of wound healing. Numerous reports have established that cells from keloid scars display Warburg metabolism—a form of JAK2/STAT3-induced metabolic adaptation typical of rapidly dividing cells in which glycolysis becomes the predominant source of ATP over oxidative phosphorylation (OxPhos). Using the JAK1/2 inhibitor ruxolitinib, along with cells from patients with STAT3 loss of function (STA3 LOF; autosomal dominant hyper IgE syndrome) we examined the role of JAK/STAT signaling in the hyperproliferation and metabolic dysregulation seen in keloid fibroblasts. Although ruxolitinib inhibited hyperactivity in the scratch assay in keloid fibroblasts, it paradoxically exacerbated the hyper-glycolytic state, possibly by further limiting OxPhos via alterations in mitochondrial phosphorylated STAT3 (pSTAT3^Ser727). In healthy volunteer fibroblasts, folic acid exposure recapitulated the exaggerated closure and hyper-glycolytic state of keloid fibroblasts through JAK1/2- and STAT3-dependent pathways. Although additional studies are needed before extrapolating from a representative cell line to keloids writ large, our results provide novel insights into the metabolic consequences of STAT3 dysfunction, suggest a possible role for folate metabolism in the pathogenesis of keloid scars, and offer in vitro pre-clinical data supporting considerations of clinical trials for ruxolitinib in keloid disorder.

Bilayer dissolving microneedle array containing 5-fluorouracil and triamcinolone with biphasic release profile for hypertrophic scar therapy

Hypertrophic scar (HS) is an undesirable skin abnormality following deep burns or operations. Although intralesional multi-injection with the suspension of triamcinolone acetonide (TA) and 5-fluorouracil (5-Fu) has exhibited great promise to HS treatment in clinical, the difference of metabolic behavior between TA and 5-Fu remarkably compromised the treatment efficacy. Besides, the traditional injection with great pain is highly dependent on the skill of the experts, which results in poor compliance. Herein, a bilayer dissolving microneedle (BMN) containing TA and 5-Fu (TA-5-Fu-BMN) with biphasic release profile was designed for HS therapy. Equipped with several micro-scale needle tips, the BMN could be self-pressed into the HS with uniform drug distribution and less pain. Both in vitro permeation and in vivo HS retention tests revealed that TA and 5-Fu could coexist in the scar tissue for a sufficient time period due to the well-designed biphasic release property. Subsequently, the rabbit ear HS model was established to assess therapeutic efficacy. The histological analysis showed that TA-5-Fu-BMN could significantly reduce abnormal fibroblast proliferation and collagen fiber deposition. It was also found that the value of scar elevation index was ameliorated to a basal level, together with the downregulation of mRNA and protein expression of Collagen I (Col I) and transforming growth factor-β1 (TGF-β1) after application of TA-5-Fu-BMN. In conclusion, the BMN with biphasic release profiles could serve as a potential strategy for HS treatment providing both convenient administrations as well as controlled drug release behavior.

•

A bilayer microneedle co-delivery system was designed for hypertrophic scar therapy.

•

The system contained rapid release triamcinolone and sustained-release 5- Fluorouracil.

•

The system was constructed to control the intralesional retention of different drugs.

•

The co-delivery system showed a superior therapeutic effect in hypertrophic scar.