Conjugation of a zwitterionic polymer with dimethyl chains to lipase significantly increases the enzyme activity and stability

Enzyme-polymer conjugates are complex molecules with great practical significance.This work was designed to develop a novel enzyme-polymer conjugate by covalently coupling a zwitterionic polymer with side dimethyl chains(pID)to Candida rugosa lipase(CRL)via the reaction between the anhydrides of polymer chains with the amino groups of the enzyme.The resulting two CRL-pID conjugates with different pID grafting densities were investigated in term of the catalytic activity,stability and structural changes.In comparison with native CRL,both the CRL conjugates displayed 2.2 times higher activity than the native enzyme,and showed an increase in the maximum reaction rate(V_(max))and a decrease in the Michaelis constant(K_(m)),thus resulting in about three-fold increases in the catalytic efficiency(k_(cat)/K_(m)).These are mainly attributed to the activation of lipase by the hydrophobic alky side chains.Moreover,the thermostability and pH tolerance of the lipase conjugates were significantly enhanced due to the stabilizing effect of the zwitterion moieties.For instance,a five-fold increase of the enzyme half-life at 50℃ for the high-pID conjugated CRL was observed.Spectroscopic studies reveal that the pID conjugation protected the enzyme in the changes in its microenvironment and conformation,well correlating with enhanced activity and stability of lipase conjugates.The findings indicate that enzyme conjugation to the zwitterionic polymer is promising for improving enzyme performance and deserves further development.

A zwitterionic polymer-inspired material mediated efficient CRISPR-Cas9 gene editing

The typeⅡ prokaryotic CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 (CRISPR/Cas9) adaptive immune system is a cutting-edge genome-editing toolbox.However,its applications are still limited by its inefficient transduction.Herein,we present a novel gene vector,the zwitterionic polymer-inspired material with branched structure (ZEBRA) for efficient CRISPR/Cas9 delivery.Polo-like kinase 1 (PLK1) acts as a master regulator of mitosis and overexpresses in multiple tumor cells.The Cas9 and single guide sgRNA (sgRNA)-encoded plasmid was transduced to knockout Plk1 gene,which was expected to inhibit the expression of PLK1.Our studies demonstrated that ZEBRA enabled to transduce the CRISPR/Cas9 system with large size into the cells efficiently.The transduction with ZEBRA was cell line dependent,which showed~10-fold higher in CD44-positive cancer cell lines compared with CD44-negative ones.Furthermore,ZEBRA induced highlevel expression of Cas9 proteins by the delivery of CRISPR/Cas9 and efficient gene editing of Plk1 gene,and inhibited the tumor cell growth significantly.This zwitterionic polymerinspired material is an effective and targeted gene delivery vector and further studies are required to explore its potential in gene delivery applications.

Zwitterionic polymers:Addressing the barriers for drug delivery

Nanocarriers play an important role in drug delivery for disease treatment.However,nanocarriers face a series of physiological barriers after administration such as blood clearance,nonspecific tissue/cell localization,poor cellular uptake,and endosome trapping.These physiological barriers seriously reduce the accumulation of drugs in target action site,which results in poor therapeutic efficiency.Although polyethylene glycol(PEG)can increase the blood circulation time of nanocarriers,its application is limited due to the“PEG dilemma”.Zwitterionic polymers have been emerging as an appealing alternative to PEG owing to their excellent performance in resisting nonspecific protein adsorption.Importantly,the diverse structures bring functional versatility to zwitterionic polymers beyond nonfouling.This review focuses on the structures and characters of zwitterionic polymers,and will discuss and summarize the application of zwitterionic polymers for drug delivery.We will highlight the strategies of zwitterionic polymers to address the physiological barriers during drug delivery.Finally,we will give some suggestions that can be utilized for the development of zwitterionic polymers for drug delivery.This review will also provide an outlook for this field.Our aim is to provide a comprehensive and systemic review on the application of zwitterionic polymers for drug delivery and promote the development of zwitterionic polymers.

Impact of the polymer backbone chemistry on interactions of amino-acid-derived zwitterionic polymers with cells

Zwitterionic polymers are known to interact with cells and have been shown to reveal cancer cell specificity.In this work,the importance of the chemistry of the polymer backbone for the cellular specificity of amino-acid-derived polyzwitterions is demonstrated.A series of glutamic acid(Glu)-based vinyl monomers(i.e.,an acrylate,a methacrylate,an acrylamide,and a methacrylamide)were prepared and used for reversible addition-fragmentation chain-transfer(RAFT)polymerisation,yielding defined polymers with narrow size distribution(Ð<1.3).All Glu-functionalised,zwitterionic polymers revealed high cytocompatibility;however,differences in cellular association and specificity were observed.In particular,the methacrylamide-derived polymers showed high association with both,breast cancer cells and non-cancerous dendritic cells and,consequently,lack specificity.In contrast,high specificity to only breast cancer cells was observed for polyacrylates,-methacrylates,and-acrylamides.Detailed analysis of the polymers revealed differences in hydrophobicity,zeta potential,and potential side chain hydrolysis,which are impacted by the polymer backbone and might be responsible for the altered the cell association of these polymers.It is shown that a slightly negative net charge is preferred over a neutral charge to retain cell specificity.This was also confirmed by association experiments in the presence of competitive amino acid transporter substrates.The affinity of slightly negatively charged Glu-derived polymers to the xCT Glu/cystine cell membrane antiporter was found to be higher than that of neutrally charged polymers.Our results emphasise the importance of the polymer backbone for the design of cell-specific polymers.This study further highlights the potential to tailor amino-acid-derived zwitterionic materials beyond their side chain functionality.

Programming Shape-Morphing Behavior of Zwitterionic Polymer/Liquid Crystal Composite with Humidity-responsive Self-healing Performance

In this study,a zwitterionic polymer/liquid crystals composite film with programming shape-morphing behavior and humidityresponsive self-healing performance was prepared by blending a zwitterionic polymer and liquid crystalline azobenzene compound in solution,followed by film-forming in a mold without tedious or multistep synthetic route.The as-obtained zwitterionic polymer/liquid crystal composite film exhibited programming shape-morphing behavior under different stimuli.In this process,the temporary shape of the composite film was memorized after the removal of the stimuli.Such characteristics would fit the requirements of intelligence and energy-saving for stimuliresponsive shape-changing materials.Moreover,the composite film showed humidity-responsive self-healing performances under wet conditions at room temperature.In summary,the simple design and preparation route of the zwitterionic polymer/liquid crystal composite film with programming shape-morphing behavior and mild condition-responsive self-healing performance look promising for the fabrication and practical application of novel photo-driven devices and soft robotics.

Recent advances in zwitterionic nanoscale drug delivery systems to overcome biological barriers

Nanoscale drug delivery systems(nDDS)have been employed widely in enhancing the therapeutic efficacy of drugs against diseases with reduced side effects.Although several nDDS have been successfully approved for clinical use up to now,biological barriers between the administration site and the target site hinder the wider clinical adoption of nDDS in disease treatment.Polyethylene glycol(PEG)-modification(or PEGylation)has been regarded as the gold standard for stabilising nDDS in complex biological environment.However,the accelerated blood clearance(ABC)of PEGylated nDDS after repeated injections becomes great challenges for their clinical applications.Zwitterionic polymer,a novel family of antifouling materials,have evolved as an alternative to PEG due to their super-hydrophilicity and biocompatibility.Zwitterionic nDDS could avoid the generation of ABC phenomenon and exhibit longer blood circulation time than the PEGylated analogues.More impressively,zwitterionic nDDS have recently been shown to overcome multiple biological barriers such as nonspecific organ distribution,pressure gradients,impermeable cell membranes and lysosomal degradation without the need of any complex chemical modifications.The realization of overcoming multiple biological barriers by zwitterionic nDDS may simplify the current overly complex design of nDDS,which could facilitate their better clinical translation.Herein,we summarise the recent progress of zwitterionic nDDS at overcoming various biological barriers and analyse their underlyingmechanisms.Finally,prospects and challenges are introduced to guide the rational design of zwitterionic nDDS for disease treatment.

Grafting Branch Length and Density Dependent Performance of Zwitterionic Polymer Decorated Polypropylene Membrane

Branch length and density have critical effects on membrane performances; however, it is regarded to be traditionally difficult to investigate the relationship due to the uncontrolled membrane modification methods. In this study, zwitterionic polymer with controlled grafting branch chain length（degree of polymerization） and grafting density（grafting chains per membrane area） was tethered to the microporous polypropylene membrane surface based on the combination of reversible addition-fragmentation chain transfer（RAFT） polymerization technique with click reaction. The modified membranes were tested by filtrating protein dispersion to highlight the correlations of branch chain length and grafting density with the membrane permeation performances. The pure water flux, the flux recovery ratio are positively and significantly, and the irreversible fouling negatively and significantly correlated with grafting density. These results demonstrate that the larger the coverage of the membrane with poly{[2-（methacryloyloxy）ethyl]-dimethyl-（3-sulfopropyl） ammonium hydroxide}（PMEDSAH）, the higher the pure water flux and the higher the flux recover ratio, and the lower the irreversible fouling, which shows that high grafting density is favorable to fouling reducing.

Structures,properties,and applications of zwitterionic polymers

Zwitterionic polymers have attracted research attention in recent years owing to their unique molecular struc-tures.In the same repeat unit,positive and negative charges are simultaneously located on a pair of cationic and anionic groups;therefore,zwitterionic polymers have a large dipole moment and numerous charged groups.Al-though the molecular chain of the zwitterionic polymer can be maintained in an electrically neutral state overall,the coexistence of the oppositely charged groups confers extremely high polarity and excellent hydrophilicity to the polymer.At the same time,the electricality of the polymer can be further regulated by the environmental pH and salt ions,which greatly broadens the scope of applications in different fields.This review introduces various structures of zwitterionic polymers and analyzes the reasons why zwitterionic polymers exhibit pH responsive-ness,anti-polyelectrolyte effects,and superior electrical conductivity.The application fields are also summarized by generalizing the research status of zwitterionic polymers,including applications in antifouling coatings,drug delivery,wastewater treatment,and sensors,etc.

Preparation and characterization of enzyme-responsive zwitterionic nanoparticles for monoclonal antibody delivery

Monoclonal antibodies have been used in many diseases,but how to improve their delivery efficiency is still a key issue.As the modification of zwitterionic polymers can maintain the stability and biological activity of monoclonal antibodies,in this study,zwitterionic monomers,sulfobetaine methacrylate(SBMA),and 3-[[2-(methacryloyloxy)ethyl]dimethylammonio]propionate(CBMA)were used to prepare monoclonal antibody-loaded zwitterionic nanoparticles with the aid of the crosslinker of MMP-2 enzyme-responsive peptide which was a rapid synthesis process under mild conditions.The results from dynamic light scattering(DLS),Fourier transform infrared spectroscopy(FTIR)and transmission electron microscopy(TEM)indicated that a series of zwitterionic nanoparticles had been successfully prepared by the in situ free radical polymerization using the MMP-2 enzyme-responsive peptide as the cross-linking agent.These nanoparticles were spherical with the sizes of(18.7±1.9)nm(SBMA nanoparticle)and(18.2±2.1)nm(CBMA nanoparticle),and the surface contained zwitterionic polymers.It was revealed that they had no cytotoxicity,could be released in tumor microenvironment by enzyme to inhibit the growth of tumor cells,and was able to effectively penetrate endothelial cells(>2%)by transwell.Therefore,the development of this strategy has a great prospect for the delivery of monoclonal antibodies.

Zwitterionic comb-like lipid polymers encapsulating linalool for increasing the fragrance retention time

Fragrances are widely used in cosmetics,apparel and detergents.However,the rapid evaporation of the aro ma shortens the useful life of the aromatic product.Therefore,improving the fragrance retention time of aromatic products and prolonging the service life of aromatic products are the key scientific problems that need to be solved in current aromatic products.In this study,zwitterionic comb-like lipid polymers were synthesized to encapsulate the fragrance molecule linalool.The results showed that the zwitterionic comb lipid molecules were capable of encapsulating more linalool than linear lipid molecules.At the same time,the zwitterionic comb-like lipid molecules also limited the slow release rate of the aroma,thereby increasing the fragrance retention time of the nano-fragrance.

Polydopamine/poly(sulfobetaine methacrylate)Co-deposition coatings triggered by CuSO_(4)/H_(2)O_(2)on implants for improved surface hemocompatibility and antibacterial activity

Implanted biomaterials such as medical catheters are prone to be adhered by proteins,platelets and bacteria due to their surface hydrophobicity characteristics,and then induce related infections and thrombosis.Hence,the development of a versatile strategy to endow surfaces with antibacterial and antifouling functions is particularly significant for blood-contacting materials.In this work,CuSO_(4)/H_(2)O_(2)was used to trigger polydopamine(PDA)and poly-(sulfobetaine methacrylate)(PSBMA)co-deposition process to endow polyurethane(PU)antibacterial and antifouling surface(PU/PDA(Cu)/PSBMA).The zwitterions contained in the PU/PDA(Cu)/PSBMA coating can significantly improve surface wettability to reduce protein adsorption,thereby improving its blood compatibility.In addition,the copper ions released from the metal-phenolic networks(MPNs)imparted them more than 90%antibacterial activity against E.coli and S.aureus.Notably,PU/PDA(Cu)/PSBMA also exhibits excellent performance in vivo mouse catheter-related infections models.Thus,the PU/PDA(Cu)/PSBMA has great application potential for developing multifunctional surface coatings for blood-contacting materials so as to improve antibacterial and anticoagulant properties.

Gelatin-based composite hydrogels with biomimetic lubrication and sustained drug release

The occurrence of osteoarthritis is closely related to progressive and irreversible destruction of the articular cartilage,which increases the friction significantly and causes further inflammation of the joint.Thus,a scaffold for articular cartilage defects should be developed via lubrication restoration and drug intervention.In this study,we successfully synthesized gelatin-based composite hydrogels,namely GelMA–PAM–PMPC,with the properties of biomimetic lubrication and sustained drug release by photopolymerization of methacrylic anhydride modified gelatin(GelMA),acrylamide(AM),and 2-methacryloyloxyethyl phosphorylcholine(MPC).Tribological test showed that the composite hydrogels remarkably enhanced lubrication due to the hydration lubrication mechanism,where a tenacious hydration shell was formed around the zwitterionic phosphocholine headgroups.In addition,drug release test indicated that the composite hydrogels efficiently encapsulated an anti-inflammatory drug(diclofenac sodium)and achieved sustained release.Furthermore,the in vitro test revealed that the composite hydrogels were biocompatible,and the mRNA expression of both anabolic and catabolic genes of the articular cartilage was suitably regulated.This indicated that the composite hydrogels could effectively protect chondrocytes from inflammatory cytokine-induced degeneration.In summary,the composite hydrogels that provide biomimetic hydration lubrication and sustained local drug release represent a promising scaffold for cartilage defects in the treatment of osteoarthritis.

Novel polyzwitterion shell with adaptable surface chemistry engineered to enhance anti-fouling and intracellular imaging of detonation nanodiamonds under tumor pHe

In this work,zwitterionic polymer(polyzwitterion)coated nanodiamonds(ND)with tumorous pH responsiveness were prepared for efficient application of commercial NDS in tumor cells imaging.Poly(carboxybetaine methacrylate)was firstly grafted on the pristine NDS(PCBMA-@-NDs)by surface-initiated reversible addition-fragmentation chain transfer(RAFT)polymerization.To achieve pH responsiveness and activated interaction with tumor cells,PCBMA-@-NDs were subsequently modified with benzene sulfonamide(PCBSA-@-NDs)via one step carbodiimide chemistry.The surface polymer functionalization was characterized by FTIR,1H NMR and TGA,and PCBMA-@-NDs and PCBSA-@-NDs showed great dispersibility,enhanced fluorescence intensity and excellent antifouling property in contrast to pristine NDs.Moreover,PCBSA-@-NDs was able to switch zwitterionic surface(at pH 7.4)reversibly into positive charge(at pH 6.5)via protonated or deprotonated acylsulfonamide.As expected,PCBSA-@-NDS demonstrated higher cell affinity and better imaging performance than those of zwitterionic NDS at tumor slight acid environment,proven by fluorescence microscopy and flow cytometry.Overall,we provide a feasible and valuable strategy to construct smart NDS,thus encouraging the application of cost-effective fluorescence nanomater-ials in biomedical fields.