Synthesis and characterization of water-soluble C60-peptide conjugates

With the aim of developing biocompatible and water-soluble C60 derivatives, three types of C60-peptide conjugates consisting of hydrophilic oligopeptide anchors (oligo-Lys, oligo-Glu, and oligo-Arg) were synthesized. A previously reported Prato reaction adduct of a biscarboxylic acid-substituted C60 derivative was subjected to a solid phase synthesis for amide formation with N-terminal amines of peptides on resin to successfully provide C60-peptide conjugates with one C60 and two peptide anchors as water-soluble moieties. Among three C60-peptide conjugates prepared, C60-oligo-Lys was soluble in water at neutral pH, and C60-oligo-Glu was soluble in buffer with a higher pH value, but C60-oligo-Arg was insoluble in water and most other solvents. C60-oligo-Lys and C60-oligo-Glu were characterized by 1H and 13C NMR. Photoinduced 1O2 generation was observed in the most soluble C60-oligo-Lys conjugate under visible light irradiation (527 nm) to show the potential of this highly water-soluble molecule in biological systems, for example, as a photosensitizer in photodynamic therapy.

Assemblies of poly(N-vinyl-2-pyrrolidone)-based double hydrophilic block copolymers triggered by lanthanide ions: characterization and evaluation of their properties as MRI contrast agents

Because of the formation of specific antibodies to poly(ethylene glycol) (PEG) leading to life-threatening side effects, there is an increasing need to develop alternatives to treatments and diagnostic methods based on PEGylated copolymers. Block copolymers comprising a poly(N-vinyl-2-pyrrolidone) (PVP) segment can be used for the design of such vectors without any PEG block. As an example, a poly(acrylic acid)-block-poly(N-vinyl-2-pyrrolidone) (PAA-b-PVP) copolymer with controlled composition and molar mass is synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. Mixing this copolymer with lanthanide cations (Gd³⁺, Eu³⁺, Y³⁺) leads to the formation of hybrid polyion complexes with increased stability, preventing the lanthanide cytotoxicity and in vitro cell penetration. These new nanocarriers exhibit enhanced T₁ MRI contrast, when intravenously administered into mice. No leaching of gadolinium ions is detected from such hybrid complexes.

Versatile thiolactone-based conjugation strategies to polymer stabilizers for multifunctional upconverting nanoparticles aqueous dispersions

We describe here a new methodology for the synthesis of well-defined phosphonic acid-terminated poly(ethylene glycol) (PEG) and RAFT-derived poly(N-vinylpyrrolidone) (PVP) and poly(N-vinylcaprolactam) (PVCL) by amine-thiol-ene and amine-thiol-thiosulfonate conjugation strategies using a phosphonated thiolactone and their use to prepare stable, water-dispersible multifunctional upconverting luminescent nanohybrids.

Bioconjugation of papain with poly(N-vinylpyrrolidone): NMR characterization and study of its enzymatic activity

A poly(vinylpyrrolidone) end-functionalized with a carboxylic acid group (PVP–CO2H) was synthesized by reversible addition-fragmentation chain transfer (RAFT)/macromolecular design via the interchange of xanthates (MADIX) polymerization mediated by 4-(O-ethylxanthyl)methyl benzoic acid. The molecular weight of the as-synthesized PVP–CO2H was estimated through UV–vis spectroscopy (Mn(UV–vis) = 7322 g/mol), gel permeation chromatography (GPC) (Mn(GPC) = 8670 g/mol), and 1H NMR, (Mn(NMR) = 8207 g/mol). The values obtained were close with the theoretical molecular weight (Mn(th) = 7925 g/mol). Subsequently, the preformed PVP–CO2H was activated to produce N-succinimidyl poly(vinylpyrrolidone) (PVP–NHS). This precursor was covalently coupled to papain to produce bioconjugate PVP–papain. The functional group modifications in the PVP chain-end were observed by the variations in the chemical shift values by 1H and 13C NMR and FTIR analysis at each step of the synthesis. The molecular weight of the PVP–papain was obtained by SEC–HPLC and suggests that, on average, four or five chains of PVP–CO2H were attached to one papain molecule. Compared with papain, the PVP–papain exhibited significantly improved catalytic activity, pH, and thermal stability. Additionally, the storage studies showed that the catalytic activity of PVP–papain was about 79% versus the native enzyme (29%), and this activity was maintained even when it was stored for 25 days.

Precise synthesis of double-armed polymers with fullerene C60 at the junction for controlled architecture

We report the first successful synthesis of the polymer-attached 1,2-hydrofullerene and the double-armed 1,4-bisadducts in a regioselective manner via controlled radical reactions.

Translatable High Drug Loading Drug Delivery Systems Based on Biocompatible Polymer Nanocarriers

Most nanocarriers possess low drug loading, resulting in frequently repeated administration and thereby high cost and increased side effects. Furthermore, the characteristics of nanocarrier materials, especially the drug loading capacity, plays a vital role in the drug delivery efficacy. In this review, we focus on the readily translatable polymeric drug delivery systems with high drug loading, which are comprised of biocompatible polymers such as poly(ethylene glycol), poly( N-vinylpyrrolidone), polyoxazoline, natural proteins like albumin and casein, non-natural proteins such as recombinant elastin-like polypeptides, as well as nucleic acids. At the end of this review, applications of these polymeric nanocarriers on the delivery of proteins and gene drugs are also briefly discussed.

Micelle vs. vesicle formation controlled by distal functionalization of C60-PEG conjugates

An amphiphilic C₆₀-PEG conjugate was modified by the addition of cationic moieties in the hydrophobic C₆₀ part to provide the related bis- and tris-adducts and their self-assembling structures were compared. All of these materials were water-soluble and their supramolecular structures were investigated in the aqueous phase using tensiometry, DLS, and STEM techniques. While mono- and bis-adducts formed micelle-type supramolecular structures, the tris-one with two additional cationic pyrrolidine groups showed the formation of larger particles as indicated by DLS data. Further, the STEM image of the tris-adduct showed a vesicle-type supramolecular structure with, presumably, an internal water-phase inside.

RAFT polymerization to form stimuli-responsive polymers

Stimuli-responsive polymers respond to a variety of external stimuli, which include optical, electrical, thermal, mechanical, redox, pH, chemical, environmental and biological signals. This paper is concerned with the process of forming such polymers by RAFT polymerization.

Recent advances in organic–inorganic well-defined hybrid polymers using controlled living radical polymerization techniques

Controlled living radical polymerizations, such as ATRP and RAFT polymerization, could be utilized for the preparation of well-defined organic–inorganic hybrid polymers based on POSS, PDMS, silica nanoparticles, graphene, CNTs and fullerene.