Targeting And Mimicking Collagen Via Triple Helical Peptides

As the most abundant protein in human body,collagen plays an essential role in regulating fundamental physiological functions such as cell differentiation,adhesion and migration,tissue regeneration and new cell formation,and its malfunction results in various diseases such as Osteogenesis Imperfecta,arthritis,thrombosis,and cancer.Therefore,the development of efficient assays for collagen is critical for the diagnosis and treatment of these diseases.As a natural biological resource,collagen possesses the unparalleled biofunctionality,biocompatibility,biodegradability and low immunogenicity when compared with synthetic materials,leading to broad application in tissue engineering and drug delivery.Due to the severe defects such as high purification cost,difficult size control,and risk of virus contamination,it is in urgent need to create novel peptides to mimic natural collagen.The work of this dissertation focuses on the the development of novel strategies for targeting and mimicking collagen.1)Bisensors based on the two-dimensional layered nanomaterials transition metal dichalcogenides such as WS₂ and MoS₂ have shown promising sensing applications using single stranded DNA as the probe biomolecule.The coupling of transition metal dichalcogenides nanosheets with other biomolecules to construct novel biosensors has great potential in a wide range of biomedical field. Herein we have designed novel WS₂-and MoS₂-based biosensing platforms using peptides as probe biomolecules,and demonstrated its application for the detection of collagen biomarkers.It opens great opportunities for the construction of novel multifunctional WS₂-and MoS₂-based biosensing platforms by integrating WS₂ and MoS₂ nanosheets with many other biomolecules.2)Collagen contains plenty charged amino acids,the detection of highly charged collagen fragments is therefore critical for the characterization of collagen diseases.We herein for the first time construct a sensing platform conjugating TPE-modified triple helical peptide probe with graphene oxide,which has shown highly sensitive and selective detection of charged collagen sequence.It may provide a prototype for the construction of novel AIE-based biosensors integrated with AIE-probe peptides and GO,extending their applications in biological analysis.3)Collagen with single amino acid substitution is the main cause of a plethora of heritable disorders such as Osteogenesis Imperfecta;howerver,the effective assay to distuigh collagen mutant from its wild type remains absent.A novel fluorescent self-quenching assay using two probe peptides has been constructed to detect target collagen peptides with single amino acid mutation at nM level.To our knowledge,our work may be the first report of a robust analytical assay that can identify collagen fragments with single amino acid mutation,which greatly contribute to deciphering the molecular mechanism of Osteogenesis Imperfecta as well as developing novel diagnostic strategies.4)The heterogeneous chain composition and fibrous nanostructure is critical for the physiological function of Type I collagen,however,success has only been achieved for the construction of self-assembling homotrimer peptides to mimic collagen till date.We herein for the time create heterotrimer collagen mimetic peptides,which can assemble to form well-ordered nanofibers under the trigger of lanthanide ions.These self-assembling heterotrimer peptides can better mimic the chain composition of collagen,and provide novel opportunities for deciphering the underlying mechanism of collagen interactions and diseases.5)Significant progress has been achieved to construct self-assembling peptides to mimic the fibrous nanostructure of native collagen,while it is still very demanding to fabricate peptide assemblies that can recapitulate both structural and biofunctional features of collagen.Herein collagen mimetic peptides have been designed to contain special amino acid sequences and the integrin-binding motif GFOGER,which can assemble to form nanofibers with excellent cell adhesion features characteristic of natural collagen under the trigger of lanthanide ions.This peptide-lanthanide ion system provides a facile approach to create nanofibers that mimic both structural and functional properties of native collagen,and opens fascinating opportunities in the development of improved functional biomaterials in tissue engineering and drug delivery.6)Osteogenesis Imperfecta is a hereditary connective tissue disorder mainly due to missense mutations in collagen,which involves complicated consequences on stability and conformationof monomer collagen as well as morphology and bioactivity of aggregated collagen.We have created a self-assembling collagen mimetic peptide system that for the first time facilitates simultaneous characterization of the effects of osteogenesis imperfecta mutations on stability, conformation,assembly and activity.The introduction of a Gly-Ala mutation leads to disrupted triple helix structure,abnormal assembly and loss of activity.The self-assembling collagen peptide system provides a robust platform to evaluate OI mutations at multiple levels varying from solution structure to assembly and function.