In vitro comparison of human plasma-based and self-assembled tissue-engineered skin substitutes:two different manufacturing processes for the treatment of deep and difficult to heal injuries

Background:The aim of this in vitro study was to compare side-by-side two models of human bilayered tissue-engineered skin substitutes(hbTESSs)designed for the treatment of severely burned patients.These are the scaffold-free self-assembled skin substitute(SASS)and the human plasma-based skin substitute(HPSS).Methods:Fibroblasts and keratinocytes from three humans were extracted from skin biopsies(N=3)and cells from the same donor were used to produce both hbTESS models.For SASS manu-facture,keratinocytes were seeded over three self-assembled dermal sheets comprising fibroblasts and the extracellular matrix they produced(n=12),while for HPSS production,keratinocytes were cultured over hydrogels composed of fibroblasts embedded in either plasma as unique biomaterial(Fibrin),plasma combined with hyaluronic acid(Fibrin-HA)or plasma combined with collagen(Fibrin-Col)(n/biomaterial=9).The production time was 46-55 days for SASSs and 32-39 days for HPSSs.Substitutes were characterized by histology,mechanical testing,PrestoBlue™-assay,immunofluorescence(Ki67,Keratin(K)10,K15,K19,Loricrin,type IV collagen)and Western blot(type I and IV collagens).Results:The SASSs were more resistant to tensile forces(p-value<0.01)but less elastic(p-value<0.001)compared to HPSSs.A higher number of proliferative Ki67+cells were found in SASSs although their metabolic activity was lower.After epidermal differentiation,no significant difference was observed in the expression of K10,K15,K19 and Loricrin.Overall,the production of type I and type IV collagens and the adhesive strength of the dermal-epidermal junction was higher in SASSs.Conclusions:This study demonstrates,for the first time,that both hbTESS models present similar in vitro biological characteristics.However,mechanical properties differ and future in vivo experiments will aim to compare their wound healing potential.

Innate and adaptive immune responses toward nanomedicines

Since the commercialization of the frst liposomes used for drug delivery,Doxil/Caelyx® and Myocet®,tremendous progress has been made in understanding interactions between nanomedicines and biological systems.Fundamental work at the interface of engineering and medicine has allowed nanomedicines to deliver therapeutic small molecules and nucleic acids more effciently.While nanomedicines are used in oncology for immunotherapy or to deliver combinations of cytotoxics,the clinical successes of gene silencing approaches like patisiran lipid complexes(Onpattro®)have paved the way for a variety of therapies beyond cancer.In parallel,the global severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)pandemic has highlighted the potential of mR NA vaccines to develop immunization strategies at unprecedented speed.To rationally design therapeutic and vaccines,chemists,materials scientists,and drug delivery experts need to better understand how nanotechnologies interact with the immune system.This review presents a comprehensive overview of the innate and adaptative immune systems and emphasizes the intricate mechanisms through which nanomedicines interact with these biological functions.