Detection Of Disease Markers With Peptide Nano-soft Materials

Polypeptide is a type of bio-macro-molecule uniquely formed by a variety of amino acid moieties inter-connected all by amide bonds.These amino acids all have similar structures but different “R” side groups.The difference between these R groups offers diversity of peptide structure,bio-chemical and bio-physical property.Therefore,amino acids with different R groups can compose a variety of functionally different polypeptides through the simple re-arrangement and combination of amino acid motifs.These functional peptides have promising applications in the field of electrochemical biosensing.The advantages of peptides are evident: they are simple to synthesize,ready to be chemically modified,possessing good chemical stability in long term storage,resistant to degradation,and they can be integrated with other methods or technologies with not much foreseeable difficulty.Therefore,in recent years,peptide and peptide-based nano materials have shown application prospects in the field of biomedicine.An electrochemical biosensor is a biosensing device that employs an electrode as for signal conversion,on this “working electrode”,is immobilized a biologically sensitive substance,as the “sensing element”,to visualize the result of the sensing process,a voltage scan is applied to the device to induce varied current through the device,as a “signal readout”.Over the last two decades,researchers have significantly extended the field of electrochemical biosensing,while new electrochemical biosensing methods are still being conceived today.The advantage of adopting electrochemical sensing system as the platform for our works lies in our understanding of this system as a sensing system of simple and compact design,it does not require expensive equipment,demanding no over-complicated experimental procedure that may necessarily introduce many a factor of uncertainty.Besides,based on the works of fore runner researchers of electrochemical biosensing,it is clear that this sensing platform is easy to construct,possessing high sensitivity,and is environmentally friendly.It is nearly the ideal platform for beginners of biosensor development.Research purpose: our works use peptide as the targeting probes to capture disease markers,during this process,via electrochemical manipulation of the chemo-physical parameters of the sensing surface,a peptide-based 2D soft nano material is formed,leading tothe formation of a more robust and reliable sensing surface.The specific binding between polypeptides and their corresponding disease markers to induce covalent bonding between them,therefore excluding the interference of foreign impurities and interfering species,while at the same an effective signal amplification strategy is also afforded by this covalent sensing complex formed by the probe and the target,leading to highly sensitive and quantitative detection of disease biomarkers.The two main experimental works are as follows:(1)Platelet-Driven Formation of Interface Peptide Nano-network Biosensor Enabling a Non-invasive Means for Early Detection of Alzheimer's DiseaseThe social and economic burden of neurodegenerative diseases such as Alzheimer's disease(AD)are more and more keenly felt by many a country experiencing population ageing.Although these diseases are currently without effective treatment,the early diagnosis of these conditions may still help to alleviate the accompanied social burden.Soft material fabricated from DNA origami or peptide cross-linking may be promising theranostic platforms in the future;however,their naturally occurring counterparts,such as the peptide aggregates in the neurodegenerative diseases,constitute an increasingly burdensome issue of public health.Thus,a design of artificial peptide nano-network biosensor is conceived,in an attempt to combat the natural pathological peptides,by mimicking their pathogenesis process.Specifically,periphery platelet can secrete A-beta and induce its cross-linking & aggregation to form surface peptide nano-network,resulting in large numbers of poly-tyrosine strands being covalently trapped in the network to serve as an efficient signal amplifier,through the electrochemical oxidation of tyrosine.This method is sensitive and quantitative in the range of normal and pathological periphery platelet distribution and can effectively discriminate Alzheimer's disease(AD)patients based on the detected potential neurodegenerative activity of platelet.These results may point to some future perspective of this method in the early screening of AD.Conclusion: By designing a peptide probe using platelet-catalyzed A? architecture,a bionic sensing system used to simulate the neurodegenerative process,a method to judge the potential of neurodegenerativeness by evaluating peripheral platelets can be established.The degree reflects the actual degree and process of neurodegeneration in the central nervoussystem.(2)Electrochemical Cross-Linking and Cleavage Enables Molecular Gaping and Bridging on a Biosensing SurfaceProtein detection in complicated biological samples requires robust design and violent rinsing.Many recently developed artificial targeting probes,however,often do not possess antibody-like binding strength to endure hush biosensing conditions;while the classic 2-to-1sandwich binding pattern are unavailable for many targets,often necessitating complicated indirect signal converting mechanism.Here attempt is made to provide novel “covalent”solution to such problems by employing peptide reactivity to form covalent and robust biosensing structure upon target binding.Both the cross-coupling and cleavage of peptide chains are employed to achieve the classic 2-to-1 binding when only one targeting probe is available.Specifically,a targeting probe against the protein and a signaling probe are co-immobilized onto the sensing interface.The ratio between the two probes and their surface density is modulated so that direct cross-linking between the two immobilized probes is suppressed by the average distance between two such probes.Upon protein binding,the protein molecule may bridge that gap by itself.The signaling probe can carry any motif of signal amplification.And here a Cu ion complexed motif,which can exhibit peroxidase-like activity upon electrochemical agitation,is employed multi-purposely,as the catalyst for cross-linking,cleavage and signal amplification.Three non-homologous target proteins can be sensitively quantified in serum-spiked samples while clinical sample detection of one of them is also successful,these results may suggest the potential of the proposed method in clinical application in the future.Using Cu ions as a catalyst,the N-terminal free amino group is removed from the terminal oxidation.Use the size and size of peptide probes and target proteins to design sensing schemes.The protein-targeted probe and the signal probe are fixed together on the sensing interface.The targeting probe contains a tyrosine moiety to facilitate recognition and induce covalent coupling to the target.The signal probe contains an N-terminal cleavable amino acid,and the Cu ion binding motif and tyrosine moiety can cross-link the protein with the target.Since the average distance between two fixed probes can suppress direct cross-linking between the two fixed probes,the ratio between the two probes and their surfacedensity can be adjusted.After copper ion-catalyzed electrochemical cross-cutting and cleavage,the signal probe near the target protein can be transferred to the target,and other probes of the signal probe can be cleaved from the sensing interface by copper ion-induced N-terminal amino acid cleavage Cracked.Conclusion: The formed covalent probe-protein-probe complex can well resist detergent rinsing,thus achieving excellent biosensing in complex samples.