Investigation of nonfouling polypeptides of poly(glutamic acid) with lysine side chains synthesized by EDC·HCl/HOBt chemistry

Poly(Glutamic Acid-Lysine) Hydrogels with Alternating Sequence Resist the Foreign Body Response in Rodents and Non-Human Primates

The foreign body response (FBR) to implanted biomaterials and biomedical devices can severely impede their functionality and even lead to failure. The discovery of effective anti-FBR materials remains a formidable challenge. Inspire by the enrichment of glutamic acid (E) and lysine (K) residues on human protein surfaces, a class of zwitterionic polypeptide (ZIP) hydrogels with alternating E and K sequences to mitigate the FBR is prepared. When subcutaneously implanted, the ZIP hydrogels caused minimal inflammation after 2 weeks and no obvious collagen capsulation after 6 months in mice. Importantly, these hydrogels effectively resisted the FBR in non-human primate models for at least 2 months. In addition, the enzymatic degradability of the gel can be controlled by adjusting the crosslinking degree or the optical isomerism of amino acid monomers. The long-term FBR resistance and controlled degradability of ZIP hydrogels open up new possibilities for a broad range of biomedical applications.

Development of Nonfouling Zwitterionic Copolymerized Peptides Based on Glutamic Acid and Lysine Dimers for Adjustable Enzymatic Degradation

Nonspecific protein adsorption-resistant materials, the so-called nonfouling materials, are crucial biomaterials in biomedical applications. Up-to-date, little attention was paid to the biodegradability of these materials. In this work, nonfouling zwitterionic copolymerized peptides composed of the N-l-glumatyl-l-lysine dimer (EK) and δ-l-lysinyl-l-glutamic acid dimer (E-K, glutamic acid with the lysine side chain) at various ratios were synthesized to investigate the enzymatic degradation rate. Two types of proteases (trypsin and alkaline protease), which represent a site-specific and less site-specific cleavage protease, respectively, were used to demonstrate the adjustable degradability by tracking the molecular weight (M_w) at different digestion times. Results showed that higher compositions of the E-K dimer lead to slower degradation rates by both proteases and larger fragments after 120 min digestion. With the composition of the E-K dimer over 50%, the degradation of copolymerized peptides by both proteases becomes very slow. This indicated that the bulky lysinyl side chain on E-K can alter the enzymolysis process for adjusting the enzymatic degradability of the newly synthesized zwitterionic copolymerized peptides, which could be promising candidates for biomedical applications in vivo.

A novel dual sensitive polymer-gambogic acid conjugate: synthesis, characterization, and in vitro evaluation

Currently, bio-simulate drug delivery systems are highly considered for efficient targeting of tumors. Nevertheless, there are some potential problems such as intelligent release efficiency, subsequently, influence cell toxicity and blood circulation stability. A novel type of stimuli-responsive nanoparticle was developed in accordance with the specific tumor microenvironment to deliver gambogic acid (GA). Herein, we successfully connected GA with mPEG via two different sensitive linkages, valine-citrulline (VC) and cystamine. The structure was characterized by ESI-MS, ¹H NMR, FT-IR or MALDI-TOF-MS. The mPEG-VC-SS-GA-NPs (PVSG-NPs) were rapidly prepared. The properties of nanoparticles, including solubility, particle size, morphology, and sensitive drug release performance, were investigated. Compared to single sensitive conjugate (mPEG-SS-GA-NPs, PSG-NPs), PVSG-NPs demonstrated greater solubility and higher sensitive release profile. Cytotoxicity test indicated that PVSG-NPs had apparent cytotoxicity on HepG2 cells and reduced cytotoxicity on normal cells. Additionally, PVSG-NPs mainly kill HepG2 cells by inducing early and late apoptosis and restraining the G0/G1 phase proliferation. Albumin adsorption test revealed that the PVSG-NPs had little albumin combination, consequently, enhancing their circulation constancy. In summary, our findings suggested the novel PVSG-NPs capable of being used for tumor targeting and further practical applications.

In Situ Fluorescence Tracking Toxic Metabolite Mono-2-ethylhexyl phthalate (MEHP) of Di-(2-ethylhexyl) phthalate (DEHP) in HeLa Cells

In this study, we synthesized a small molecule fluorescent probe for detecting mono-2-ethylhexyl phthalate (MEHP) named MEHP-AF, which formed by MEHP cross-linked with 5-aminofluorescein (5-AF) through amide bond. MEHP-AF had been purified based on the different physicochemical properties of 5-AF with MEHP. MEHP-AF showed fluorescence characteristics coming from 5-AF and liposoluble property coming from MEHP. After physicochemical characterization, a series of biological studies of its action in cells were carried out. The results indicated that MEHP-AF was a fluorescent probe with strong specificity and high sensitivity. It can visibly track the location of MEHP in HeLa cell or subcellular levels under confocal laser scanning microscopy in situ. This novel fluorescent probe is expected to use for studying its intracellular behavior at the cell level, especially for investigating the interaction between MEHP and cellular molecules.

Development of polypeptide-based zwitterionic amphiphilic micelles for nanodrug delivery

Protein molecules, which typically have a hydrophobic core and a zwitterionic shell with a polypeptide backbone, could be ideal materials for nanodrug vehicles (NDVs) with low side effects. Here, we synthesized poly(l-aspartic acid(lysine))-b-poly(l-lysine(Z)) (PAsp(Lys)-b-PLys(Z)) (PALLZ), a novel amphiphilic block polypeptide with key structures of protein to investigate the possibility for use as a NDV. This polypeptide can spontaneously self-assemble into micelles in aqueous solution with a zwitterionic brush (the PAsp(Lys) part) to provide the nonfouling shell and a hydrophobic core (the PLys(Z) part) for loading hydrophobic drugs. The doxorubicin (DOX) loaded PALLZ micelles showed excellent resistance to nonspecific protein adsorption in FBS, which leads to very low internalization. Moreover, PALLZ micelles showed no cytotoxicity to MCF7, HeLa and HepG-2 cells up to 500 μg mL^-1. All these results indicated that zwitterionic amphiphilic block polypeptides could be promising materials for NDVs.