Zwitterionic Polymer: A New Paradigm for Protein Conjugation beyond PEG

Mitigating Membrane Biofouling in Protein Production with Zwitterionic Peptides

Biofouling on polymeric membranes poses a significant challenge in protein production and separation processes. We report here on the use of zwitterionic peptides composed of alternating lysine (K) and glutamic acid (E) residues to reduce biomolecular fouling on gold substrates and polymeric membranes within a protein production-mimicking environment. Our findings demonstrate that both gold chips and polymeric membranes functionalized with longer sequence zwitterionic peptides, along with a hydrophilic linker, exhibit superior antifouling performance across various protein-rich environments. Furthermore, increasing the grafting density of these peptides on substrates enhances their antifouling properties. We believe that this work sheds light on the antifouling capabilities of zwitterionic peptides in cell culture environments, advancing our understanding and paving the way for the development of zwitterionic peptide-based antifouling materials for polymeric membranes.

Responsive Degradable Bottlebrush Polymers Enable Drugs With Superior Efficacy and Minimal Systemic Toxicity

Bottlebrush polymers (BBPs) have garnered significant attention as advanced drug delivery systems, capable of transporting a diverse range of therapeutic agents, including both chemical drugs and biologics. Despite their effectiveness, the empty BBP vectors post-drug release may pose long-term safety risks due to their difficult systemic clearance. Here, a responsive degradable BBP platform for cancer therapy is developed, featuring a poly(disulfide) backbone grafted with fluorine-terminated zwitterionic side chains. Anti-cancer drugs are tethered to the backbone via a clinically approved valine-citrulline (VC) linker. This design leverages the tumor's reductive environment and Cathepsin B overexpression for BBP rapid degradation and precise drug release restricted within tumor cells, thereby addressing systemic safety concerns over synthetic BBP and expanding the therapeutic window of anti-cancer drugs simultaneously. Surface fluorination of BBP further enhances tumor accumulation and deep penetration. In vivo studies with monomethyl auristatin E (MMAE)-loaded BBP in tumor-bearing mice demonstrate substantial tumor suppression with minimal side effects. Together, these findings highlight the potential of responsive degradable BBP as a versatile unimolecular platform for cancer drug delivery, addressing existing challenges associated with synthetic BBP nanomedicines.

Ultrastable and Redispersible Zwitterionic Bottlebrush Micelles for Drug Delivery

Bottlebrush copolymers are increasingly used for drug delivery and biological imaging applications in part due to the enhanced thermodynamic stability of their self-assemblies. Herein, we discuss the effect of hydrophilic block chemistry on the stability of bottlebrush micelles. Amphiphilic bottlebrushes with zwitterionic poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) and nonionic polyethylene glycol (PEG) hydrophilic blocks were synthesized by "grafting from" polymerization and self-assembled into well-defined spherical micelles. Colloidal stability and stability against disassembly were challenged under high concentrations of NaCl, MgSO4, sodium dodecyl sulfate, fetal bovine serum, and elevated temperature. While both types of micelles appeared to be stable in many of these conditions, those with a PMPC shell consistently surpassed their PEG analogs. Moreover, when repeatedly subjected to lyophilization/resuspension cycles, PMPC micelles redispersed with no apparent variation in size or dispersity even in the absence of a cryoprotectant; PEG micelles readily aggregated. The observed excellent stability of PMPC micelles is attributed to the low critical micelle concentration of the bottlebrushes as well as to the strong hydration shell caused by ionic solvation of the phosphorylcholine moieties. Zwitterionic micelles were loaded with doxorubicin, and higher loading capacity/efficiency, as well as delayed release, was observed with increasing side-chain length. Finally, hemocompatibility studies of PMPC micelles demonstrated no disruption to the red blood cell membranes. The growing concern regarding the immunogenicity of PEG-based systems propels the search for alternative hydrophilic polymers; in this respect and for their outstanding stability, zwitterionic bottlebrush micelles represent excellent candidates for drug delivery and bioimaging applications.

Innovative Formulation Platform: Paving the Way for Superior Protein Therapeutics with Enhanced Efficacy and Broadened Applications

Protein therapeutics offer high therapeutic potency and specificity; the broader adoptions and development of protein therapeutics, however, have been constricted by their intrinsic limitations such as inadequate stability, immunogenicity, suboptimal pharmacokinetics and biodistribution, and off-target effects. This review describes a platform technology that formulates individual protein molecules with a thin formulation layer of crosslinked polymers, which confers the protein therapeutics with high activity, enhanced stability, controlled release capability, reduced immunogenicity, improved pharmacokinetics and biodistribution, and ability to cross the blood brain barriers. Based on currently approved protein therapeutics, this formulating platform affords the development of a vast family of superior protein therapeutics with improved efficacy and broadened indications at significantly reduced cost.

Study of uricase-polynorbornene conjugates derived from grafting-from ring-opening metathesis polymerization

PEGylation has been the 'gold standard' in bioconjugation due to its ability to improve the pharmacokinetics and pharmacodynamics of native proteins. However, growing clinical evidence of hypersensitivity reactions to PEG due to pre-existing anti-PEG antibodies in healthy humans have raised concerns. Advancements in controlled polymerization techniques and conjugation chemistries have paved the way for the development of protein-polymer conjugates that can circumvent these adverse reactions while retaining the benefits of such modifications. Herein, we show the development of polynorbornene based bioconjugates of therapeutically relevant urate oxidase (UO) enzymes used in the treatment of gout synthesized by grafting-from ring-opening metathesis polymerization (ROMP). Notably, these conjugates exhibit comparable levels of bioactivity to PEGylated UO and demonstrate increased stability across varying temperatures and pH conditions. Immune recognition of conjugates by anti-UO antibodies reveal low protein immunogenicity following the conjugation process. Additionally, UO conjugates employing zwitterionic polynorbornene successfully avoid recognition by anti-PEG antibodies, further highlighting a potential replacement for PEG.