L-asparaginase immobilization in supramolecular nanogels of PEG-grafted poly HPMA and bis(α-cyclodextrin) to enhance pharmacokinetics and lower enzyme antigenicity

L-asparaginase (ASNase) enzyme has limited therapeutic use due to its poor pharmacokinetics and immunogenicity. To overcome these obstacles, we immobilized ASNase in biocompatible poly hydroxypropyl methacrylamide (P(HPMA))-based nanogels simply formed through the host-guest inclusion complex of ASNase-conjugated random copolymer of HPMA and polyethylene glycol (PEG) acrylate (P(HPMA-MPEGA)) and α-cyclodextrin dimer (bisCD) using cystamine as a linker. The effects of bisCD and polymer concentrations on particle size, gelation time, and recovery of enzyme activity were investigated. The ASNase-conjugated bisCD nanogels were discrete, homogeneous, and spherical with a mean projected diameter of 148 ± 41 nm. ASNase immobilized in the bisCD nanogels caused cytotoxicity on HL-60 cell line with IC₅₀ of 3 IU/ml. In-vivo rat study revealed that the immobilized ASNase reduced the enzyme antigenicity and resulted in 8.1 folds longer circulation half-life than the native enzyme. Conclusively, immobilization of ASNase in P(HPMA-MPEGA) and bisCD supramolecular nanogels could enhance the therapeutic value of ASNase in cancer chemotherapy.

Safety and Biodistribution Profile of Poly(styrenyl acetal trehalose) and Its Granulocyte Colony Stimulating Factor Conjugate

Poly(styrenyl acetal trehalose) (pSAT), composed of trehalose side chains linked to a polystyrene backbone via acetals, stabilizes a variety of proteins and enzymes against fluctuations in temperature. A promising application of pSAT is conjugation of the polymer to therapeutic proteins to reduce renal clearance. To explore this possibility, the safety of the polymer was first studied. Investigation of acute toxicity of pSAT in mice showed that there were no adverse effects of the polymer at a high (10 mg/kg) concentration. The immune response (antipolymer antibody and cytokine production) in mice was also studied. No significant antipolymer IgG was detected for pSAT, and only a transient and low level of IgM was elicited. pSAT was also safe in terms of cytokine response. The polymer was then conjugated to a granulocyte colony stimulating factor (GCSF), a therapeutic protein that is approved by the Federal Drug Administration, in order to study the biodistribution of a pSAT conjugate. A site-selective, two-step synthesis approach was developed for efficient conjugate preparation for the biodistribution study resulting in 90% conjugation efficiency. The organ distribution of GCSF-pSAT was measured by positron emission tomography and compared to controls GCSF and GCSF-poly(ethylene glycol), which confirmed that the trehalose polymer conjugate improved the in vivo half-life of the protein by reducing renal clearance. These findings suggest that trehalose styrenyl polymers are promising for use in therapeutic protein-polymer conjugates for reduced renal clearance of the biomolecule.

Polymer-drug conjugates: Design principles, emerging synthetic strategies and clinical overview

Adagen, an enzyme replacement treatment for adenosine deaminase deficiency, was the first protein-polymer conjugate to be approved in early 1990s. Post this regulatory approval, numerous polymeric drugs and polymeric nanoparticles have entered the market as advanced or next-generation polymer-based therapeutics, while many others have currently been tested clinically. The polymer conjugation to therapeutic moiety offers several advantages, like enhanced solubilization of drug, controlled release, reduced immunogenicity, and prolonged circulation. The present review intends to highlight considerations in the design of therapeutically effective polymer-drug conjugates (PDCs), including the choice of linker chemistry. The potential synthetic strategies to formulate PDCs have been discussed along with recent advancements in the different types of PDCs, i.e., polymer-small molecular weight drug conjugates, polymer-protein conjugates, and stimuli-responsive PDCs, which are under clinical/preclinical investigation. Current impediments and regulatory hurdles hindering the clinical translation of PDC into effective therapeutic regimens for the amelioration of disease conditions have been addressed.

Novel self-assembled nanogels of PEG-grafted poly HPMA with bis(α-cyclodextrin) containing disulfide linkage: synthesis, bio-disintegration, and in vivo biocompatibility

Synthesis of self-assembled nanogels of PEG-grafted poly HPMA with bis(α-cyclodextrin) containing disulfide linkage.

Weaving Enzymes with Polymeric Shells for Biomedical Applications

Enzyme therapeutics have received increasing attention due to their high biological specificity, outstanding catalytic efficiency, and impressive therapeutic outcomes. Protecting and delivering enzymes into target cells while retaining enzyme catalytic efficiency is a big challenge. Wrapping of enzymes with rational designed polymer shells, rather than trapping them into large nanoparticles such as liposomes, have been widely explored because they can protect the folded state of the enzyme and make post-functionalization easier. In this review, the methods for wrapping up enzymes with protective polymer shells are mainly focused on. It is aimed to provide a toolbox for the rational design of polymeric enzymes by introducing methods for the preparation of polymeric enzymes including physical adsorption and chemical conjugation with specific examples of these conjugates/hybrid applications. Finally, a conclusion is drawn and key points are emphasized.

Covalent Immobilization of L-Asparaginase and Optimization of Its Enzyme Reactor for Reducing Acrylamide Formation in a Heated Food Model System

Acrylamide is a potent carcinogen and neurotoxin that is mainly formed by the Maillard reaction of asparagine with starch at high temperatures. In this work, a food safety immobilization system for L-asparaginase (L-ASNase) consisting of food-grade agarose (Aga) spheres and N-hydroxysuccinimide esters was developed to decrease the formation of acrylamide in a fluid food model system. L-asparaginase was successfully immobilized with a maximum immobilization efficiency of 68.43%. The immobilized enzymes exhibited superior storage stability and reusability with 93.21 and 72.25% of the initial activity retained after six consecutive cycles and storage for 28 days, indicating its high industrial application potential. Meanwhile, a simplified mathematical model of the enzyme reactor was developed and verified with experiments, which demonstrated its auxiliary role in the design and optimization of reactors. In addition, simulated fluidized food components were continuously catalyzed in the designed packed bed reactor, achieving a reduction rate of nearly 89%.