Influence of Block versus Random Monomer Distribution on the Cellular Uptake of Hydrophilic Copolymers

How does the polymer architecture and position of cationic charges affect cell viability?

Polymer chemistry, composition and molar mass are factors that are known to affect cytotoxicity, however the influence of polymer architecture has not been investigated systematically. In this study the influence of the position of the cationic charges along the polymer chain on cytotoxicity was investigated while keeping constant the other polymer characteristics. Specifically, copolymers of various architectures, based on a cationic pH responsive monomer, 2-(dimethylamino)ethyl methacrylate (DMAEMA) and a non-ionic hydrophilic monomer, oligo(ethylene glycol)methyl ether methacrylate (OEGMA) were engineered and their toxicity towards a panel of cell lines investigated. Of the seven different polymer architectures examined, the block-like structures were less cytotoxic than statistical or gradient/tapered architectures. These findings will assist in developing future vectors for nucleic acid delivery.

Influence of Monomer Structures for Polymeric Multivalent Ligands: Consideration of the Molecular Mobility of Glycopolymers

Molecular mobility is important for interactions of biofunctional polymers with target molecules. Monomer structures for synthetic biofunctional polymers are usually selected based on their compatibility with polymerization systems, whereas the influence of monomer structures on the interaction with target molecules is hardly considered. In this report, we evaluate the correlation between the monomer structures of glycopolymers and their interactions with concanavalin A (ConA) with respect to the molecular mobility. Two types of glycopolymers bearing mannose are synthesized with acrylamide or acrylate monomers. Despite the similar structures, except for amide or ester bonds in the side chains, the acrylate-type glycopolymers exhibit stronger interaction with ConA both in the isothermal titration calorimetry measurement and in a hemagglutination inhibition assay. Characterization of the acrylate-type glycopolymers suggests that the higher binding constant arises from the higher molecular mobility of mannose units, which results from the rotational freedom of ester bonds in their side chains.

Evaluating Endosomal Escape of Caspase-3-Containing Nanomaterials Using Split GFP

The ability for biologics to access intracellular targets hinges on the translocation of active, unmodified proteins. This is often achieved using nanoscale formulations, which enter cells through endocytosis. This uptake mechanism often limits the therapeutic potential of the biologics, as the propensity of the nanocarrier to escape the endosome becomes the key determinant. To appropriately evaluate and compare competing delivery systems of disparate compositions, it is therefore critical to assess endosomal escape efficiencies. Unfortunately, quantitative tools to assess endosomal escape are lacking, and standard approaches often lead to an erroneous interpretation of cytosolic localization. In this study we use a split-complementation endosomal escape (SEE) assay to evaluate levels of cytosolic caspase-3 following delivery by polymer nanogels and mesoporous silica nanoparticles. In particular, we use SEE as a means to enable the systematic investigation of the effect of polymer composition, polymer architecture (random vs block), hydrophobicity, and surface functionality. Although polymer structure had little influence on endosomal escape, nanogel functionalization with cationic and pH-sensitive peptides significantly enhanced endosomal escape levels and, further, significantly increased the amount of nanogel per endosome. This work serves as a guide for developing an optimal caspase-3 delivery system, as this caspase-3 variant can be easily substituted for a therapeutic caspase-3 cargo in any system that results in cytosolic accumulation and cargo release. In addition, these data provide a framework that can be readily applied to a wide variety of protein cargos to assess the independent contributions of both uptake and endosomal escape of a wide range of protein delivery vehicles.

Aqueous solubilization of hydrophobic tetrapyrrole macrocycles by attachment to an amphiphilic single-chain nanoparticle (SCNP)

Snapping a heterotelechelic amphiphilic polymer onto a tetrapyrrole imparts aqueous solubility to the otherwise hydrophobic macrocycle as demonstrated for a chlorin, bacteriochlorin and phthalocyanine.

Role of hydrophobicity in tuning the intracellular uptake of dendron-based fluorophores for in vitro metal ion sensing

Fluorophores are used for sensing biologically relevant ions, toxic metals or pathogenic markers. However, the mode of entry of such fluorophores into the cell greatly depends on their size, shape, surface charge, functional groups, and hydrophobicity. In particular, the influence of hydrophobicity on the intracellular uptake of fluorophores is poorly investigated. Self-assembly is a recent strategy to tune the intracellular uptake of fluorophores, facilitating increased intracellular sensing and fluorescence. Herein, self-assembly of three novel poly(aryl ether) dendron derivatives that contain rhodamine units was used to investigate the effect of hydrophobicity on the intracellular uptake of self-assembled fluorophores. The results suggest that monomer hydrophobicity plays an important role in the uptake. The dendron-based fluorophores, which upon self-assembly, formed stable spherical aggregates ranging from 300 to 500 nm. The rhodamine-based dendrons could selectively sense Hg²⁺ ions in the presence of other competing metal cations. Intracellular imaging of the dendron-based fluorophores displayed bright red fluorescence in human embryonic kidney cells. The rate of intracellular uptake of the three dendron-based fluorophores was analyzed by flow cytometry. The results establish the importance of the hydrophilic-lipophilic balance of the self-assembled amphiphiles for tuning the intracellular uptake.

Trehalose-functional glycopeptide enhances glycerol-free cryopreservation of red blood cells

Arginine- and trehalose-modified ε-polylysine (ε-PL) demonstrated a high synergistic function with trehalose for RBC cryopreservation.

Polymer-Temozolomide Conjugates as Therapeutics for Treating Glioblastoma

A series of polymer-drug conjugates based on 2-methacryloyloxyethyl phosphorylcholine (MPC) was prepared with the glioblastoma drug temozolomide (TMZ) as pendent groups. Random and block copolymers were synthesized by reversible addition-fragmentation chain-transfer (RAFT) polymerization using a TMZ-containing methacrylate monomer. The solution properties of the polyMPC-TMZ copolymers were investigated by dynamic light scattering and transmission electron microscopy, revealing well-defined nanostructures from the block copolymers. Conjugation of TMZ to polyMPC enhanced drug stability, with decomposition half-life values ranging from 2- to 19-times longer than that of free TMZ. The cytotoxicity of polyMPC-TMZ was evaluated in both chemosensitive (U87MG) and chemoresistant (T98G) glioblastoma cell lines. Furthermore, the polyMPC-TMZ platform was expanded considerably by the preparation of redox-sensitive polyMPC-TMZ copolymers utilizing disulfides as the polymer-to-drug linker.

Reverse-phase high performance liquid chromatography (RP-HPLC) as a powerful tool to characterise complex water-soluble copolymer architectures

A novel analytical method, based on RP-HPLC, for the characterisation of monomer distribution in charged water-soluble copolymers.

Anionic multiblock core cross-linked star copolymers via RAFT polymerization

The synthesis of (multi)block copolymers sand star (multiblock) copolymers of poly(2-acrylamido-2-methylpropane sulfonic acid) by RAFT polymerisation is reported.

Polymer synthesis by mimicking nature's strategy: the combination of ultra-fast RAFT and the Biginelli reaction

A two-stage method has been developed by mimicking nature's protein synthesis strategy to prepare plenty of polymers using limited monomers.