Construction And Application Of Biomimetic Smart Matrices For Preventing Fibrotic Scarring Of Skin Wound

Skin is the body's largest organ that is the first barrier against the damage of the external environment and plays critical roles in maintaining homeostasis and health.Trauma?burn?injury is the most widespread and the fourth most common type of injury in the world.However,it is still challenging public health problems worldwide in effective wound healing and skin regeneration.In more recent years,the mortality and recovery for severe trauma?burn?injuries have improved significantly due to the knowledge of the molecular and cellular biology of wound healing and the application of advanced materials and techniques.Unfortunately,irreversible fibrotic skin scarring after wound repair causes severe physical and mental trauma for the patients,in addition to be one of the formidable clinic challenges in biomedical and tissue engineering regeneration fields.In this thesis,based on molecular biological mechanisms during wound healing and the critical factors associated with fibrotic skin scarring,we exert to solve issues of cutaneous fibrotic scarring via biomimetic strategies.Since inherent oxidative stress is the main factor of fibrotic skin scarring for burn injury,we developed a multi-dimensional injectable antioxidant defense hydrogel?MICH?matrix with removing various?Reactive oxygen species?ROS from intracellular and extracellular ROS as well as those in the cytomembrane inspired by the cellular antioxidant defense system.This MICH was applied to deep second-degree burns for preventing fibrotic scarring of skin wound.Given molecular biological mechanisms during wound healing and inspired by fetal scarless wound healing,we developed a wearable biomimetic film?WBMF?mimicking the characteristics of fetal skin.This WBMF is applied to the large area of full-thickness excisional skin model for evaluating the effect of WBMF on anti-fibrotic skin scarring.The main results are as follows:?1?Construction and performance of anti-fibrotic active molecular carrier with controlled-release through mimicking enzymes:Vitamin E?VE?is the natural anti-fibrotic bioactive molecules in the body.Based on the cavity effect of?-cyclodextrin??-CD?similar to enzyme mechanism,four types of?-CD amino derivatives were synthesized by the single substitution modification of the 6-position hydroxyl group of?-CD using ethylenediamine,long-chain polyether amine and aromatic amine?dopamine,DA?,respectively.The four types of?-CD amino derivatives were severed as host molecules to recognize guest VE and yield host-guest inclusions?-CD/VE,?-CD-6-EDA/VE,?-CD-6-D400/VE,?-CD-6-D2000/VE and?-CD-6-DA/VE.The order of encapsulation efficiency of host molecules on VE was?-CD-6-D2000>?-CD-6-DA>?-CD-6-D400/VE>>?-CD-6-EDA>?-CD as the amount of substance of host molecules were same.Also,the host-guest inclusive proportions of?-CD-6-D2000/VE and?-CD-6-DA/VE were found to be 1:1,which were higher than that of?-CD/VE inclusion?2:1?.Besides,?-CD-6-D2000/VE and?-CD-6-DA/VE inclusive complexes exhibited 35?-responsive release performance,long-term stability in the natural environment,and excellent scavenging activities on intracellular and extracellular ROS.?2?Construction and performance of injectable biomimetic antioxidant defense hydrogel?MICH?matrix:Burn-mediated oxidative stress is the critical factor for skin fibrosis.Inspired by cellular antioxidant defense system,we developed an in situ forming,injectable,antioxidant defense hydrogel matrix through chemical grafting,catechol-Fe³⁺coordination,and host-guest interaction,in which hyaluronan?HA?was served as the cell signal transduction medium,VE as small molecule antioxidants,and catechol-Fe³⁺coordination as“Fe-SOD”mimic.The MICH matrix showed in situ instant gelling performance,pH-responsive property?p H?6.0 or 7.4?sensitive to oxidative stress lesions,and stress-responsive capacity.In the antioxidant model through chemical reactions,the MICH matrix exhibited almost 100%of ROS scavenging activities,including O₂^×-,×OH,DPPH×,and ABTS^×+.In the H₂O₂-induced NIH-3T3 fibroblast?NIH-3T3?oxidative stress model,the MICH matrix exhibited a positive concentration correlation of oxidative stress defense performance.Also,the MICH matrix showed 100%of scavenging activity on intracellular ROS and ROS in cytomembrance at a 600?g m L^-1 of concentration.In the meantime,the MICH matrix up-regulated protein activities of the endogenous antioxidant enzymes?SOD,CAT,and GSH-Px?,prevented cell apoptosis,and recovered damaged cells to normal cell viability and morphologies.?3?Treatment effects of MICH matrix on the deep second-degree burns in mice skin:Deep second-degree burned oxidative stress model in mice skin was successfully built by controlling temperature.Injectable MICH was applied to wound beds,showing that the MICH matrix was capable of integrating with wound tissue quickly to provide a microenvironment of tissue hydration and extracellular matrix required for burn wounds.Furthermore,the MICH matrix significantly inhibited the activity of xanthine oxidase?XO?and malondialdehyde?MDA?in wound tissue,alleviated burn-induced oxidative stress damage and inflammatory response,and promoted reepithelialization and angiogenesis in wound tissue.Pathological sections of remodeling tissue showed more collagen fiber III and less collagen fiber I in the dermis of the remodeling tissue as well as normal dermal collagen architecture,which was similar to that of healthy mice.These results reveal that the MICH matrix prevents fibrotic scarring of burned skin and gains excellent skin regeneration.?4?Construction,performance,and anti-fibrotic therapeutic effects of the wearable biomimetic film?WBMF?mimicking the characteristics of fetal skin:Inspired by early-gestation scarless fetal wound healing,we developed a wearable biomimetic film composed of cytokines regulator HA and anti-fibrotic active molecule VE through chemical grafting,host-guest interaction,and physical self-assembling?hydrogen bonding and?–?stacking?.The WBMF exhibited seamless adhesion to skin with the adhesive strength of 20.87±8.30 kPa,which provided fetal skin context of sterility and physiological low oxygen tension.The WBMF matched anisotropic skin tension with a fracture strain of 473±25%,tensile stress modulus of0.72±0.03 MPa,hysteretic strain energy density loss of 1.79 kJ m^-3,which might protect wound tissue from secondary insults.Also,the WBMF showed persistent moisture under the conditions of 50%relative humidity and 37°C to provide high hydration microenvironment required for wound tissue.As thus,the physical characteristics and chemical composes of WBMF could create a fetal skin context and fetal extracellular matrix?ECM?once it was applied to wound beds.In the large area of full-thickness excisional skin injury model,the WBMF reduced the number of inflammatory cells,inhibited TNF-?and TGF-?1 activity levels,and alleviated inflammatory response of wound tissues.In the meantime,the WBMF induced high expression of VEGF regulated by low oxygen tension,promoted vascularization of wound granulation tissue.During tissue formation,WBMF promoted migration of keratinocytes and fibroblasts to accelerate epidermal closure.More importantly,the WBMF inhibited expression of pro-fibrotic cytokines TGF-?1 and modulated differentiation and apoptosis of myofibroblast in the middle and late phases of wound healing.Notably,the remodeling skin mediated by WBMF showed low collagen fiber deposition,uniform collagen arrangement,and normal dermal collagen architecture,thereby attaining scarless skin appearance.This work proposes that smart matrices with special treatment through biomimetic strategies enable to enhance wound healing and prevent fibrotic scarring of skin wound.The materials may find potential utility as well as provide some guidance and referential value for the fields of material science and regenerative medicine.