| The low delivery efficiency of nanomedicine has remained an unresolved issue for 30 years.Researchers striving to enhance drug delivery efficacy and efficiency using nanomaterials have adopted the straightforward approach of coupling plasma albumin with nanomaterials.This scheme endows biocompatibility and long blood circulation,offering promising prospects for targeted drug delivery systems.Protein corona exists on the surface of blood cells to evade recognition and phagocytosis of the mononuclear phagocytic system(MPS).A specific protein corona composition is essential to inhibit recognition,phagocytosis,and clearance of MPS,and different proteins on the surface of nanoparticles are necessary to prevent non-specific cell uptake.Single molecular weight polyethylene glycol(PEG)demonstrates better performance in resisting non-specific protein adsorption.Therefore,it is significant to design,develop,synthesize,and study nano-assemblies based on precise polymers and in situ covalently coupled albumin.To tackle the challenges of liver and spleen enrichment and low tumor targeting efficiency of drug delivery nanocarriers,researchers are focused on exploring protein corona regulation and precise compound construction instead of evading MPS capture through hydrophilic modification.This paper specifically studies the application of single molecular weight PEG modified carrier with a single molecular weight and nanocarriers that bind endogenous albumin through maleimide in drug delivery,controlled release,and tumor targeting.The research primarily comprises three sections:1.A series of obstacles,such as blood circulation,tissue accumulation,tissue penetration,cell internalization,and drug release,must be overcome after intravenous injection to deliver nanodrugs to the cytoplasm of solid tumor and distal tumor cells.Among the many types of nanocarriers being explored for drug delivery,serum albumin,which is the most abundant plasma protein in the blood and has an extremely long half-life of 19 days,shows great promise in designing long-cycle and targeted drug delivery systems.The molecular structure of albumin contains a free sulfhydryl group,and the maleimide(MI)group can efficiently carry out Michael addition reactions with the sulfhydryl group.Based on this,we designed different structures of linking units for the connection of cisplatin small molecule drugs and MI groups and assembled nanoparticles.During blood circulation,MI groups on the surface of nanoparticles will covalently couple with albumin to form an albumin-rich protein corona.It is important to note that within minutes of entering the bloodstream,the nanoparticles’ fate is determined by the rapid formation of protein corona on their surface.Experimental results on a series of nanoparticles with similar chemical structures show that in situ capture of albumin nanoparticles has a longer half-life,while avoiding drug enrichment in the liver and spleen and targeting tumor tissue.In addition,nanoparticles with albumin-rich corona on the surface are difficult to be quickly cleared by Kupffer cells of the liver,and can further penetrate into the tumor through vascular endothelium and into the tumor stroma through Gp60 receptor-mediated endocytosis.The remaining MI on the nanoparticles can react with the SPARC protein in the extracellular matrix,causing the particles to concentrate around the tumor cells.In addition,the nanoparticles can also be captured by free thiol groups on the cell membrane surface through the MI.After being ingested by tumor cells,the reducing microenvironment rich in glutathione(GSH)causes partial dissociation of the nanoparticles and transformation into smaller nanoparticles to achieve deep penetration of the tumor.Eventually,the nanoparticles could be used for chemotherapy by releasing small molecule cisplatin drugs through complete dissociation.2.PEGylation refers to a general method of covalently bonding or non-covalently linking PEG to small molecule drugs,contrast agents,proteins,nucleic acids,osomes,and other substances.PEGylation can improve the dispersion,stability,pharmacokinetics,and pharmacodynamics of drugs in aqueous solutions to a certain extent.However,traditional polydisperse PEGs are mixtures with varying molecular weights,which complicates the synthesis and purification of PEGylated drugs and may induce unnecessary immunogenic reactions,ultimately affecting the efficacy of drug therapy.Single molecular weight PEG has the same chemical structure as polydisperse PEG but has a precise molecular weight.Recent advances in single molecular weight PEG synthesis have allowed us to further regulate the protein corona on the surface of drug delivery carriers by modifying the end groups of PEG based on constructing precise PEGylated derivatives.A series of single molecular weight and polydisperse PEGylated dyes were synthesized,including PEGylated aggregate dye R-PEGn-IR820 and PEGylated water-soluble dye HO-PEGn-Cy7.5.Compared to polydisperse HO-PEG2000-IR820,analytical ultracentrifugation demonstrated that single molecular weight HO-PEG45-IR820 has a narrower distribution of sedimentation coefficients.HO-PEG45-IR820 exhibited a longer half-life and reduced accelerated blood clearance in vivo.MI-PEG45-IR820,containing an MI group at the end,had a more limited enrichment effect in the liver and spleen and was more conducive to cell uptake.It was further discovered that single molecular weight HO-PEG45-Cy 7.5 had a lower degree of retention in the renal site,and the fluorescence intensity of normal kidney tissues and tumor tissues was significantly different in the in situ renal carcinoma model mice.To elucidate the reasons for these phenomena,the protein corona of different samples and their production of anti-PEG antibodies in mice were studied.It has been proven that single molecular weight PEG has lower immunogenicity and weaker protein adsorption properties3.Gas-filled microbubbles(MBs)have been clinically used as ultrasound(US)contrast agents for disease diagnosis and treatment.However,it remains a great challenge to resolve the dilemma of stability and contrast enhancement of MBs.the use of perfluorocarbons(PFCs)with decreased solubility in biological fluids can effectively improve the stability of MBs.However,despite great achievements,the imaging time of these US contrast agents remains short.Moreover,the insufficient stability of MBs-based contrast agents leads to a rapid decay of US signals,rendering it unfavorable for disease diagnosis.The acoustic performance of MBs is greatly affected by the physicochemical properties of the shell materials.According to the Laplace equation,reducing the interfacial tension can effectively diminish the internal and external pressure difference of curved surfaces,thereby elevating the stability of MBs.The most widely used shell materials of MBs were phospholipids with interfacial tensions higher than 30 mN/m.In contrast,polymers with semifluoroalkyl side chains have low interfacial tension values ranging from 7 to 12 mN/m,which can efficiently improve the stability of MBs and thus represent promising alternatives to phospholipids.Therefore,in order to solve the dilemma of long-term stability and contrast enhancement of microbubble ultrasonic contrast agent.Herein,a series of amphiphilic copolypeptides is synthesized and used as shell materials to stabilize PFC-filled MBs,in which hydrophilic PEG blocks and fluorinated PFOK blocks constitute the outer and inner layers of the MB shells,respectively.The fluorinated blocks possessing both low interfacial tensions and low Laplace pressure can improve the stability of MBs when in contact with the inner octafluoropropane(C3F8)phase.In addition,copolypeptides containing cross-linkable diacetylene moieties in the side chains are also synthesized and UV-induced crosslinking of the diacetylene moieties further improves the stability of MBs,which,however,leads to decreased US signals due to suppressed nonlinear oscillation.In order to solve this issue,copolypeptides with terminal MI functional groups were created,and after the covalent conjugation of plasma proteins like albumin via in situ Michael addition reactions,the nonlinear oscillation of the resulting MI-decorated MBs can be noticeably enhanced.This work provides a new strategy to fabricate copolypeptide-stabilized MBs as highly efficient US contrast agents with long-term stability. |
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