Amphiphilic Pentablock Copolymers Prepared from Pluronic and ε-Caprolactone by Enzymatic Ring Opening Polymerization

Amphiphilic copolymers are appealing materials because of their interesting architecture and tunable properties. In view of their application in the biomedical field, the preparation of these materials should avoid the use of toxic compounds as catalysts. Therefore, enzymatic catalysis is a suitable alternative to common synthetic routes. Pentablock copolymers (CUC) were synthesized with high yields by ring-opening polymerization of ε-caprolactone (ε-CL) initiated by Pluronic (EPE) and catalyzed by Candida antarctica lipase B enzyme. The variables to study the structure–property relationship were EPEs’ molecular weight and molar ratios between ε-CL monomer and EPE macro-initiator (M/In). The obtained copolymers were chemically characterized, the molecular weight determined, and morphologies evaluated. The results suggest an interaction between the reaction time and M/In variables. There was a correlation between the differential scanning calorimetry data with those of X-ray diffraction (WAXD). The length of the central block of CUC copolymers may have an important role in the crystal formation. WAXD analyses indicated that a micro-phase separation takes place in all the prepared copolymers. Preliminary cytotoxicity experiments on the extracts of the polymer confirmed that these materials are nontoxic.

Tuning CO2-induced reversible redispersion or irreversible destabilisation for latex separation

HYPOTHESIS

The CO₂-sensitive dispersion/precipitation transition of polymer latexes fabricated based on a responsive emulsifier is a promising way to conveniently acquire bulk polymer materials. Nevertheless, the tedious synthesis procedures for switchable surfactants and the harsh operating requirements for the sensitive latexes constrain the applicability of the approach for latex preparation. Therefore, a new strategy for generating latexes with tunable CO₂ responsiveness in a maneuverable way is urgently needed.

EXPERIMENTS

In this work, a CO₂-switchable electrostatic interaction is introduced to construct responsive latexes. A series of lightly crosslinked poly(diethylaminoethyl methacrylate-styrene) [P(DEA-St)] latexes with different PDEA contents were fabricated via one-pot emulsion copolymerization, with divinylbenzene and sodium dodecylsulfate (SDS) used as the crosslinker and anionic emulsifier, respectively. The influence of the DEA feeding ratio on the resulting P(DEA-St) colloids was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Then, a cyclic CO₂/N₂ input was introduced to verify the response transitions of polymer latexes.

FINDINGS

Accompanied by the stepwise decrease of DEA feeding ratio, the morphology of the resulting copolymerized nanoparticles changed from an ambiguous bulge to the typical spherical pattern. In addition, the P(DEA-St) latexes treated by cyclic CO₂/N₂ exhibit four different types of response modes, namely (i) CO₂-switchable swelling/deswelling transition, (ii) CO₂-reversible dispersion/coagulation transition, (iii) CO₂-induced irreversible destabilisation and (iv) CO₂-insensitive latexes. The CO₂-responsive destabilisation is highly applicable in the separation and transportation fields of commercial latex products, such as poly(methyl methacrylate), poly(n-butyl acrylate) and poly(butyl methacrylate) colloids.

Polymer-based nanoparticles for protein delivery: design, strategies and applications

Therapeutic proteins have attracted significant attention as they perform vital roles in various biological processes. Polymeric nanoparticles can offer not only physical protection from environmental stimuli but also targeted delivery of such proteins to specific sites, enhancing their therapeutic efficacy.

Superoxide dismutase enzymosomes: carrier capacity optimization, in vivo behaviour and therapeutic activity

PURPOSE

A strategy not usually used to improve carrier-mediated delivery of therapeutic enzymes is the attachment of the enzymes to the outer surface of liposomes. The aim of our work was to design a new type of enzymosomes with a sufficient surface-exposed enzyme load while preserving the structural integrity of the liposomal particles and activity of the enzyme.

METHODS

The therapeutic antioxidant enzyme superoxide dismutase (SOD) was covalently attached to the distal terminus of polyethylene glycol (PEG) polymer chains, located at the surface of lipid vesicles, to obtain SOD-enzymosomes.

RESULTS

The in vivo fate of the optimized SOD-enzymosomes showed that SOD attachment at the end of the activated PEG slightly reduced the residence time of the liposome particles in the bloodstream after IV administration. The biodistribution studies showed that SOD-enzymosomes had a similar organ distribution profile to liposomes with SOD encapsulated in their aqueous interior (SOD-liposomes). SOD-enzymosomes showed earlier therapeutic activity than both SOD-liposomes and free SOD in rat adjuvant arthritis. SOD-enzymosomes, unlike SOD-liposomes, have a therapeutic effect, decreasing liver damage in a rat liver ischemia/reperfusion model.

CONCLUSIONS

SOD-enzymosomes were shown to be a new and successful therapeutic approach to oxidative stress-associated inflammatory situations/diseases.

Preparation and characterization of biodegradable amphiphilic polymers and nanoparticles with high protein-loading capacity

Multiblock copolymers containing carboxyl groups in the side-chains and at the chain ends were prepared from ABA triblock copolymers of ε-caprolactone, or lactide (as A block), and ethylene glycol (as B block). ABAn multiblock copolymers were prepared after chain-end functionalization and chain extension with pyromellitic dianhydride. A series of polymers were synthesized by varying the poly(ethylene glycol) and polyester molecular weight and the chirality of the lactide. Nuclear magnetic resonance analysis was used to confirm free carboxyl groups in the polymer backbone and at the chain ends. Thermal analysis indicated that the presence of pyromellitic dianhydride residues interfered not only with the formation of crystalline phases but also with the thermal degradation of chain-extended polymers. The biocompatibility of these amphiphilic polymers as evaluated with mouse embryo fibroblasts was acceptable. Both the parent ABA triblock copolymers and the carboxylated polymers were processed into nanoparticles. Depending on the polymer structure and reaction conditions, a narrow size nanoparticle distribution from ~10 to 250 nm was obtained. The nanoparticles were loaded with 60%–90% albumin and released 80%–90% of the albumin absorbed. Overall, this system was found to be well suited for the preparation of high-capacity injectable protein drug delivery.

Chondroitin sulfate-g-poly(ϵ-caprolactone) co-polymer aggregates as potential targeting drug carriers

The aim of this study is to delineate the effect of various amounts of hydrophobic polycaprolactone (PCL) grafted onto three different degrees of methacrylated chondroitin sulfate (CSMA) on chemical-physical properties. The co-polymers were prepared by reacting the modified PCL and the hydrophilic CSMA via a radical reaction (CSMA-PCL). The effect of degree of methacrylation of CSMA and feed ratio between CSMA and PCL on compositions and critical micelle concentrations was systematically studied. The PCL composition of the CSMA-PCL was characterized by (1)H-NMR and FT-IR. The hydrodynamic diameters and morphologies of CSMA-PCL micelles were studied by DLS and TEM. Critical micelle concentrations were determined using pyrene as a probe. Taking one of the CSMA-PCL micelles as an example, a cancer-mediated ligand, folic acid, was linked to the surface. The cellular uptake of the folic acid-linked CSMA-PCL in folate-receptor-overexpressing KB cells was studied by confocal laser scanning microscopy and flow cytometry.

Nanocarrier possibilities for functional targeting of bioactive peptides and proteins: state-of-the-art

This review attempts to provide an updated compilation of studies reported in the literature pertaining to production of nanocarriers encasing peptides and/or proteins, in a way that helps the reader direct a bibliographic search and develop an integrated perspective of the subject. Highlights are given to bioactive proteins and peptides, with a special focus on those from dairy sources (including physicochemical characteristics and properties, and biopharmaceutical application possibilities of e.g. lactoferrin and glycomacropeptide), as well as to nanocarrier functional targeting. Features associated with micro- and (multiple) nanoemulsions, micellar systems, liposomes and solid lipid nanoparticles, together with biopharmaceutical considerations, are presented in the text in a systematic fashion.

Tailoring nanocarriers for intracellular protein delivery

Proteins play a crucial role in life, taking part in all vital processes in the body. In the past decade, there was increasing interest in delivering active forms of proteins to specific cells and organs. Intracellular protein delivery holds enormous promise for biological and medical applications, including cancer therapy, vaccination, regenerative medicine, treatment for loss-of-function genetic diseases and imaging. This tutorial review surveys recent developments in intracellular protein delivery using various nanocarriers. Methods such as lipid-mediated colloidal systems, polymeric nanocarriers, inorganic systems and protein-mediated carriers are reviewed. Advantages and limitations of current strategies, as well as future opportunities and challenges are also discussed.

Targeted Delivery of Protein Drugs by Nanocarriers

Recent advances in biotechnology demonstrate that peptides and proteins are the basis of a new generation of drugs. However, the transportation of protein drugs in the body is limited by their high molecular weight, which prevents the crossing of tissue barriers, and by their short lifetime due to immuno response and enzymatic degradation. Moreover, the ability to selectively deliver drugs to target organs, tissues or cells is a major challenge in the treatment of several human diseases, including cancer. Indeed, targeted delivery can be much more efficient than systemic application, while improving bioavailability and limiting undesirable side effects. This review describes how the use of targeted nanocarriers such as nanoparticles and liposomes can improve the pharmacokinetic properties of protein drugs, thus increasing their safety and maximizing the therapeutic effect.