Polyphenol Self-Assembly Film And Its Applications In Anti-Platelet Adhesion And The Capture Of Circulating Tumor Cells

Blood-contacting materials are widely used in the field of biomedical materials.Blood-material interactions trigger a complex series of events including platelet and leukocyte adhesion,not only causing undesirable clinical outcomes(e.g.,thrombosis and inflammatory response)but also impairing the functionalities of biomaterials.Until now,the surfaces of platelet-and leukocyte-repellent materials are generally fabricated by two approaches:1)constructing bioinert surfaces by employing hydrophilic antifouling polymers;2)designing bioactive coatings with immobilization of biomolecules to inhibiting cell adhesion.However,the construction of bioinert surfaces commonly require complicated chemical synthesis and multistep surface treatments.In addition,bioactive proteins are expensive and also easy to deactivate or degrade.Inspired by the anti-platelet and anti-inflammatory effects of natural polyphenols,as well as the simple and rapid coating process of polyphenol self-assembly film,this paper proposed a strategy to construct platelet-and leukocyte-repellent materials using the polyphenol film.This paper first constructed the stable polyphenol film and then investigated the anti-platelet adhesion performance of the film.Finally,the paper examined the anti-leukocyte adhesion performance of the film and explored its application in the capture of circulating tumor cells.Firstly,this paper focused on the coating process and stability of the polyphenol film.Using tannic acid(TA)as a model polyphenol molecule,the film was prepared on the basis of the coordination between polyphenol and metal Fe3+ ions.Then,we investigated the key effects of experimental parameters(order of reagents addition,pH value of reaction solution and surface wettability of the substrates)on the thickness and stability of the film.The polyphenol film(Fe3+ ions first and then polyphenol TA)showed steady growth and obtained a stable coating with a thickness of 85 nm after five coating cycles.The pH value of reaction solution was adjusted from 3 to 8 to promote the formation of Fe-O coordination bond,resulting in a denser metal-polyphenol network and improving the stability of the film.Moreover,compared with hydrophilic surface,hydrophobic surface facilitated the formation of stable film.Then,this paper investigated the effects of the thickness of the film,the storage time under ambient condition,and the types of polyphenol molecules and substrates on the anti-platelet adhesion performance of the polyphenol film.The results showed that after five coating cycles,platelets were difficult to observe on the film with a thickness of 85 nm.After 21 days exposure to air,the film still maintained the excellent platelet-repellent capability,which was significantly better than that of the control poly(ethylene glycol)(PEG)-functionalzied materials.In addition,the platelet-repellent behavior could extend to other polyphenols-functionalized surfaces such as epigallocatechin gallate(EGCG)and epicatechin gallate(ECG)films.Moreover,the platelet-repellent property of the polyphenol film was applicable to a variety of biomedical materials(i.e.,polyether sulfone membrane,polycarbonate panel and silicone tube).This paper further investigated the mechanism of anti-platelet adhesion of the polyphenol film.Considering that the chemical groups of the film interacted with proteins were galloyl groups,we speculated that the galloyl groups may played a crucial role in the platelet repellence.Because fibrinogen(Fgn)has been identified as the key protein in the process of biomaterial-induced platelet adhesion,we first designed a series of polyphenol films with different amounts of galloyl groups and then investigated the effects of the galloyl groups on the adsorption of Fgn(amount and conformation)and the potential for platelet adherence.The experimental results indicated that these films adsorbed a similar amount of Fgn,but the conformation of the adsorbed Fgn were quite different among the films.In particular,a strong correlation was found between the degree of the exposure of the Fgn-y chain and platelet adhesion.The degree of the exposure of the Fgn-y chain and the level of platelet adhesion on the films gradually decreased with increasing the number of galloyl groups on the surfaces.The polyphenol film with the most galloyl groups could induce strongly hydrogen-bond interaction with Fgn molecule,thus inhibiting the adsorbed Fgn from undergoing conformational change.As a result,the platelet adhesion receptor of the Fgn-y chain hidden on the surface,eventually leading to the outstanding antiplatelet adhesion effect.Finally,this paper explored the potential application of the film in the capture of circulating tumor cells(CTCs).Because the undesirable leukocyte adhesion on materials surfaces would hinder the capture of CTCs,we first investigated the anti-leukocyte adhesion performance of the polyphenol film.The results showed that peripheral blood mononuclear cells(PBMCs)adhesion on substrates dramatically reduced from～74 to～11 cells/mm2 after the modification of the film.Besides,the levels of proinflammatory cytokines(TNF-a and IL-6)released by PBMCs considerably decreased in the presence of the film.Various cancer cell lines(MCF-7,A431,HeLa and A549)were then employed to exam the CTCs capture performance of the film.The results indicated that the film could effectively capture various cancer cells(yield>76%).regardless of the protein expression status on the cell surfaces.Moreover,the film also displayed excellent cytocompatibility,thus enabling the cell enrichment without compromising cell viability(>90%)and the following cell culture.In summary,the polyphenol self-assembly film provided a simple and effective strategy for constructing platelet-and leukocyte-repellent materials,which has great potential in the field of blood-contacting biomaterials.Besides,the film developed a label-free method for CTCs capture,without the introduction of traditional nanostructured surfaces,complicated microfluidic devices and any recognition biomolecules.This method would provide new clues in designing CTC-capture devices for the early diagnosis of cancer diseases.