Application Of Collagen-based Restorative Materials In The Reconstruction Of Corneal Conjunctival Ocular Surface

The eye is the main organ for human to perceive the external environment,among which the corneal conjunctival ocular surface composed of corneal epithelium and conjunctival plays an important role in protecting the eyeball and refraction.However,the corneal conjunctival ocular surface is vulnerable to inflammatory damage caused by traumatic injuries(such as chemical injuries)and degenerative diseases(such as pterygium).Currently,a variety of materials(such as autologous/allogeneic conjunctiva,amniotic membrane,acellular conjunctiva,natural biological polymers and synthetic polymers,etc.)have been used for the corneal conjunctival ocular surface reconstruction of horn conjunctiva in clinic,but the clinical therapeutic effect has been limited.The reason is not only that these materials have shortcomings such as difficulty in preparation,poor mechanical strength and risk of disease transmission,but more importantly,that these materials have not been designed according to different injury etiology and tissue repair characteristics of the corneal conjunctival ocular surface,nor have supporting reconstruction surgery methods been adopted.The ideal materials for the reconstruction of corneal conjunctival ocular surface should be adapted to the anatomical and pathological differences between corneal epithelium and conjunctiva,and be designed according to different injury causes and tissue repair characteristics.At the same time,it is an effective way to further improve the effect of reconstruction and effectively solve clinical pain points to develop supporting innovative surgical methods,stimulate the function of materials and avoid the complications caused by traditional invasive suture.In recent years,collagen repair materials have attracted extensive attention in the field of tissue repair.The natural macromolecular materials derived from biology have satisfactory biocompatibility,biodegradability,and reparation-promoting properties,which make them have broad application prospects in the field of the corneal conjunctival ocular surface repair.Based on the clinical needs and the practical application of materials,the corneal conjunctival ocular surface reconstruction collagen membranes and the supporting surgical techniques for reconstruction were designed and prepared,according to the physiological structure,injury etiology,and repair characteristics of the corneal epithelium and conjunctiva.The purpose is to achieve the effective regeneration and repair of the structure and function of the corneal and conjunctival ocular surface.In order to solve the problems in clinical practice,this paper puts forward practical and effective ideas and methods.In this paper,doxycycline(Dox),a specific inhibitor of matrix metalloproteinases(MMPs),was encapsulated in hydroxypropyl chitosan microspheres(HCM)by an improved emulsion crosslinking method.The objective is to ensure that slowly released Dox can continuously inhibit abnormal MMPs activity and promote epithelial cell regeneration and stabilization.Then,the innovative combination of HCM and collagen was used to prepare a drug-loaded collagen corneal reconstruction membrane with the ability to inhibit MMPs.The reconstructed membrane can be sutured to cover the damaged cornea,creating a microenvironment conducive to re-epithelialization while ensuring the drug release in situ.It was found that the drug release time was further extended to 10 days after loading,and the basic physicochemical properties of collagen film were not changed.Cell experiments confirmed the good biocompatibility and cell growth promotion ability of the reconstructed materials.Subsequently,the corresponding in vivo and in vitro inflammation models were constructed to verify that the materials could effectively down-regulate the m RNA expression levels of MMP-9 and MMP-13 in an inflammatory environment.In the New Zealand white rabbit corneal alkali burn model,the reconstruction material can be well sutured to cover the ocular surface.This reconstruction strategy not only prolongs drug release in situ but also constructs a microenvironment to promote epithelial repair.The results showed that the drug-loaded collagen corneal reconstruction membrane accelerated the early complete re-epithelialization of the cornea and promoted the early reconstruction of the epithelium.Due to the inherent biodegradability of HCM and collagen,the material was completely degraded and shed on the 7th day,which was consistent with the regeneration and repair process of the corneal epithelium.The results show that the drug-loaded collagen corneal reconstruction membrane has good clinical application value.Subsequently,since the conjunctiva is prone to scar repair and suture-related complications in the process of pterygium reconstruction,a collagen conjunctival reconstruction membrane with a natural layered structure and appropriate mechanical strength was screened by optimizing the preparation process.After in vitro experiment,a New Zealand white rabbit model of a large conjunctival defect was established,and conventional conjunctival reconstruction surgery was performed using the collagen conjunctival reconstruction membrane.The results showed that the material could significantly promote the migration of conjunctival cells,accelerate the early closure of the incision and promote the early functional repair of the tissue in vivo.However,postoperative observation found that the surgical procedure itself and the surgical suture will lead to inevitable complications of obvious scarring in the conjunctival tissue.Therefore,taking advantage of the natural reaction sites of tissue and collagen,this paper innovatively adopts the idea of sutureless surgery to construct a photocurable biological glue based on semi-interpenetrating polymer network(s IPN).Combined with collagen conjunctival reconstruction membrane to achieve a sutureless conjunctival reconstruction strategy.The lightcurable biological glue(GMO)based on s IPN was obtained by adjusting the ratio of Methylpropenyl acylated gelatin(Gel Ma)and oxidized hyaluronic acid(OHA).The effective adhesion performance of GMO bioadhesive was confirmed by a self-built personalized adhesion test platform.In vivo,GMO bioadhesive not only accelerated the migration of conjunctival epithelial cells but also promoted the early closure of tissue defects.More importantly,this sutureless reconstruction strategy of collagen conjunctival reconstruction membrane combined with bioadhesive avoids suture-related complications and achieves functional tissue repair without scaring,demonstrating its great potential in clinical application.It is an innovative attempt to provide clinically feasible research ideas and applied materials for corneal conjunctival ocular surface reconstruction according to the characteristics of the tissue.