Self-Assembled Amyloid Short Peptide-Based Functional Materials And Their Applications In Cancer Diagnosis And Treatment

Peptides are a class of compounds between amino acids and proteins,where 2-10amino acids are dehydrated and condensed to form short peptides.Short peptide sequences can be spontaneously assembled into diverse and highly ordered nanostructures driven by intermolecular interactions under specific solvents.Compared with small molecules,nanostructures have different surface chemistry,higher effective loading and longer half-life in vivo;compared with metal,non-metal and polymer nanomaterials,peptide-based nanomaterials have good bioactivity,biocompatibility and degradability;compared with protein-based materials,they are cost effective,environmentally tolerant,flexible in design and adjustable in structure.Structure-function modulation of peptide-based nanomaterials can be achieved by designing different short peptide sequences and changing their assembly behavior.They are good candidates for preparing biomaterials with important development prospects in biomedical fields such as drug delivery,tissue engineering,antibacterial,and biosensing.This dissertation focuses on the key problems related to cancer diagnosis and treatment:high signal-to-noise ratio sensing of target molecules in deep tissues,real-time delivery monitoring of drug molecules and improvement of photodynamic anti-cancer effects.Using short peptides with significant biological effects,a series of multiform,multiscale and multifunctional short peptide self-assembled nanoplatforms with therapeutic properties were designed and constructed from the perspective of sequence-structure-function regulation to achieve high signal-to-noise ratio bioimaging of methylglyoxal in deep tumor tissues,real-time release of therapeutic gas molecules by fluorescence visualization and efficient anticancer by multivalent targeting of cellular organelles.This dissertation is divided into five parts as follows.Chapter 1.OverviewIn this chapter,the origin of amyloid short peptide self-assembly,driving forces and external influence factors that drive self-assembly and the construction of nanomaterials at multidimensional scales were first introduced.Subsequently,we highlighted the current applications and development of peptide-based nanomaterials in biosensing,cancer treatment,light harvest and gas transport.Finally,the main content,significance and innovation of this dissertation were elaborated.Chapter 2.NIR-I fluorescence imaging tumorous methylglyoxal by an activatable nanoprobe based on peptide nanotubes by FRET processMethylglyoxal（MGO）is a major precursor for the formation of advanced glycation end products,which is closely related to the development of various diseases such as cancer and mainly relies on glyoxalase（GLO）system for detoxification in vivo.Fluorescence imaging is a favorable tool for non-destructive and in situ monitoring MGO changes.However,fluorescence emission of MGO probes were mostly located in visible region,limiting the application of bioimaging in deep tissues and a few MGO probes with near-infrared（NIR）emission were complex to synthesize.Therefore,in this chapter,we constructed a peptide-based activated nanoprobe for visual monitoring of GLO1 inhibitor-induced fluctuations in MGO levels at tumor sites in 4T1 tumor-bearing mice.IR783 and MGO probe（DBTPP）were loaded on the outer surface and inner wall of the peptide nanotubes via noncovalent interactions.The effective spectral overlap of the two probes and suitable wall thickness of peptide nanotubes（4 nm）prompted fluorescence resonance energy transfer（FRET）between IR783 and DBTPP.Taking advantage of the extended fluorescence signal,D/I-PNTs could achieve high sensitivity,selectivity and high signal-to-noise imaging of MGO in deep tissues.Such a strategy provided a universal solution for ratio detection of various target analytes in NIR region.Chapter 3.Construction of a multifunctional peptide nanoplatform for nitric oxide release and monitoring and its application in tumor-bearing miceIn recent years,gas therapies represented by nitric oxide（NO）have been gaining popularity due to their multiple effects on tumors.NO exerts either promotive or inhibitory effects on organisms depending on its concentration.Therefore,real-time monitoring of NO release is of great significance.Additionally,due to the random nature of its trajectory,gas generation in situ facilitates to maximize its effectiveness.In this chapter,we fabricated a supramolecular D-KLP₂₂ONSs based on the self-assembly of Ac-KLVFFAL-NH₂（KL-7）peptide derivatives for NIR-I imaging-guided NO delivery confirmation and gas therapy.The incorporation of a NO donor into a nanofibrillar platform generated KLP₂₂ONSs capable of inducing local and sustained NO-release.A new probe DPBTD with benzothiadiazole as the electron acceptor and o-phenylenediamine as the recognition group,as an activated NIR reporter for NO,was encapsulated into peptide scaffolds byπ-πand hydrophobic interactions and reflected the NO-release events in a noninvasive and real-time way.The nanoplatform exhibited good plasticity under sonication,allowing for triple morphological changes from linear,spindle to lamellar shapes and showing differences in cellular endocytosis.In this chapter,D-KLP₂₂ONSs offer the possibility of therapeutic gas localization,expanding the potential biological applications of peptide derivatives as gas transmitters.Chapter 4.Mitochondrial multivalent targeted peptide assemblies for photodynamic antitumor studyDepending on the reaction mechanism,photodynamic process can be divided into type I pathway,which relies on electron transfer to produce superoxide anion(O₂^?-)and type II pathway,which relies on energy transfer to produce singlet oxygen（¹O₂）.Although type II photosensitizers are more common,the problems of oxygen dependence in photodynamic processes,short half-life and limited diffusion radius of¹O₂ limit its application.In order to enhance the effect of type II photosensitizers and improve their retention time at tumor sites,in this chapter,we coupled the photosensitizer pyropheophorbide a（PPa）and the mitochondrial targeting unit triphenylphosphine（TPP）on lysine residue of KL-7,and co-assembled both of them to construct mitochondrial multivalent targeting nanorods KLTPPa for image-guided photodynamic anticancer studies.KLTPPa could directly attack organelles sensitive to reactive oxygen species（ROS）under laser irradiation and induce mitochondrial damage by generating ¹O₂,thus achieving antitumor effects,which to some extent ameliorated the limitations inherent to type II photosensitizers due to oxygen dependence and limited diffusion distance of ¹O₂.In addition,KLTPPa has demonstrated the ability of lung-specific targeting,offering the possibility of image-guided precise and efficient photodynamic therapy against lung metastases.Chapter 5.Summary and outlookIn this chapter,we have made a summary of pervious work and further expounded the significance and innovation points of this dissertation.Combined with the current research status of self-assembled peptide-based nanomaterials,the key scientific problems still need to be solved in the future have been analyzed and an outlook on opportunities for future development has been made.