Heterogeneous Brønsted Catalysis in the Solvent-Free and Multigram-Scale Synthesis of Polyalcohol Acrylates: The Case Study of Trimethylolpropane Triacrylate

This article presents a thorough investigation into the synthesis of trimethylolpropane triacrylate (TMPTA) via the esterification reaction of trimethylolpropane (TMP) with acrylic acid using Amberlite™ 120 IR (H+), Amberlyst® 15, and Dowex™ 50WX8 resins as heterogeneous catalysts. Preliminary comparative tests explored the impact of air flow on water removal during the reaction and different acid-to-alcohol molar ratios (3:1, 6:1, or 9:1 mol:mol). The findings revealed that introducing air significantly enhances TMPTA yield and -OH group conversion, particularly at a 6:1 acid-to-alcohol molar ratio. Based on cost considerations, Amberlite™ 120 IR (H+) was selected as the preferred catalyst for further optimization. This included evaluating the effect of catalyst loading (10%, 5.0%, and 2.5% w/wtot) and assessing the impact of a pre-drying process on resin efficiency. The study concluded that optimal conditions did not necessitate drying, requiring 120 °C, a catalyst loading of 10% w/wtot, a 4 h reaction time, an acid:alcohol ratio of 6:1 mol:mol, the presence of MEHQ (0.1% mol/molAA), and air bubbling at 6 ± 1 Nl/h. Catalyst recycling was effectively implemented with a slight reduction in catalytic activity over consecutive runs. Furthermore, the study explored a scaled-up system with a mechanical stirrer, demonstrating the potential for multi-hundred grams scale-up. Considerations for optimizing the air flow stripping system are also highlighted. In summary, this study provides valuable insights into designing and optimizing the esterification process for TMPTA synthesis, laying the foundation for potential industrial applications.

Complex Formation Between Lysozyme and Stabilized Micelles with a Mixed Poly(ethylene oxide)/Poly(acrylic acid) Shell

The electrostatic complexation between lysozyme and stabilized polymeric micelles (SPMs) with a poly(acrylic acid) (PAA) or a mixed poly(ethylene oxide)/poly(acrylic acid) (PEO/PAA) shell (SPMs with a mixed shell, SPMMS) and a temperature-responsive poly(propylene oxide) (PPO) core was investigated by means of dynamic, static, and electrophoretic light scattering. The SPMs and different types of SPMMS used resulted from the self-assembly of PAA-PPO-PAA triblock copolymer chains, or PAA-PPO-PAA and PEO-PPO-PEO triblock copolymer chain mixtures (with varying chain lengths and molar ratios) in aqueous solutions at pH 10 and the subsequent cross-linking of their PPO cores via loading and photo-cross-linking of pentaerythritol tetraacrylate (PETA). The solution behavior, structure and properties of the formed complexes at pH 7 and 0.01 M ionic strength, were studied as a function of the protein concentration in the solution (the concentration of the stabilized micelles was kept constant) or equivalently the ratio of the two components. The complexation process and properties of the complexes proved to be dependent on the protein concentration, while of particular interest was the effect of the structure of the shell of the SPMs on the stability/solubility of the complexes. Finally, the fluorescence and mid infrared spectroscopic investigation of the structure of the complexed protein showed that, although a small stretching of the protein molecules occurred in some cases, no protein denaturation takes place upon complexation.

Controlling the morphology of glyco-nanoparticles in water using block copolymer mixtures: the effect on cellular uptake

Poly[(2-(α-d-mannosyloxy)ethyl acrylate)-block-(n-butyl acrylate)], P(ManA-b-BA), and poly[poly(ethylene glycol) methyl ether acrylate]-block-(n-butyl acrylate)], P(OEGMEA-b-BA) diblock copolymers were mixed at various ratios to generate self-assembled structures of different morphologies.

Controlled co-delivery nanocarriers based on mixed micelles formed from cyclodextrin-conjugated and cross-linked copolymers

The combination of multiple drugs within a single nanocarrier can provide significant advantages for disease therapy and it is desirable to introduce a second drug based on host-guest interaction in these co-delivery systems. In this study, a core-stabilized mixed micellar system consisting of β-cyclodextrin-conjugated poly(lactic acid)-b-poly(ethylene glycol) (β-CD-PLA-mPEG) and DL-Thioctic acid (TA) terminated PLA-mPEG (TA-PLA-mPEG) was developed for the co-delivery of DOX and fluorescein isothiocyanate labeled adamantane (FA). DOX can be loaded within the hydrophobic segment of PLA and FA may form stable complexation with β-CD in the core. The mixed micelles (MM) are based on well-accepted medical materials and can be easily cross-linked by adding 1,4-dithio-D,L-threitol (DTT), which can enhance the stability of the system. Drug-loaded MM system was characterized in terms of particle size, morphology, drug loading and in vitro release profile. Cytotoxicity test showed that blank MM alone showed negligible cytotoxicity whereas the drug-loaded MM remained relatively high cytotoxicity for HeLa cancer cells. Confocal laser scanning microscopy (CLSM) demonstrated that the MM could efficiently deliver and release DOX and FA in the same tumor cells to effectively improve drugs' bioavailability. These results suggested that the core-stabilized MM are highly promising for intracellular co-delivery of multiple drugs.

The effect of kinetic stability on biodistribution and anti-tumor efficacy of drug-loaded biodegradable polymeric micelles

This study was aimed to investigate the effect of kinetic stability on biodistribution and antitumor efficacy of drug-loaded biodegradable polymeric micelles. Four diblock copolymers of acid- and urea-functionalized polycarbonate (i.e. PAC and PUC) and poly(ethylene glycol) (PEG) with the same polycarbonate length and two different PEG molecular weights (Mn: 5 kDa and 10 kDa), i.e. 5K PEG-PAC, 10K PEG-PAC, 5K PEG-PUC and 10K PEG-PUC, were synthesized via organocatalytic living ring-opening polymerization using methoxy PEG as a macroinitiator. These polymers were employed to prepare 5K PEG-PAC/5K PEG-PUC and 10K PEG-PAC/10K PEG-PAC mixed micelles via urea-acid hydrogen bonding. An amine group-containing anticancer drug, doxorubicin (DOX) was loaded into the mixed micelles via a self-assembly process. DOX-loaded 5K and 10K PEG mixed micelles had particle sizes of 66 and 87 nm respectively with narrow size distribution (polydispersity index: 0.12), and DOX loading levels were 28.9 and 22.8% in weight. DOX-loaded 5K PEG mixed micelles had greater kinetic stability than DOX-loaded 10K PEG mixed micelles due to stronger hydrophobicity of 5K PEG block copolymers. The results of in vitro release studies showed that DOX release was sustained without obvious initial burst release. The DOX-loaded mixed micelles effectively suppressed the proliferation of HepG2 and 4T1 cells. The in vivo studies conducted in a 4T1 mouse breast cancer model demonstrated that the mixed micelles were preferably transported to the tumor with the 5K PEG mixed micelles accumulating in the tumor more rapidly to a larger extent than 10K PEG mixed micelles, and DOX-loaded 5K PEG mixed micelles with greater kinetic stability inhibited tumor growth more effectively than free DOX and DOX-loaded 10K PEG mixed micelles without causing significant body weight loss or cardiotoxicity. The 5K PEG mixed micelles with sizes below 100 nm and narrow size distribution as well as excellent kinetic stability holds great potential as a delivery carrier for amine group-containing anticancer drugs.

Stabilized micelles as delivery vehicles for paclitaxel

Paclitaxel is an antineoplastic drug used against a variety of tumors, but its low aqueous solubility and active removal caused by P-glycoprotein in the intestinal cells hinder its oral administration. In our study, new type of stabilized Pluronic micelles were developed and evaluated as carriers for paclitaxel delivery via oral or intravenous route. The pre-stabilized micelles were loaded with paclitaxel by simple solvent/evaporation technique achieving high encapsulation efficiency of approximately 70%. Gastrointestinal transit of the developed micelles was evaluated by oral administration of rhodamine-labeled micelles in rats. Our results showed prolonged gastrointestinal residence of the marker encapsulated into micelles, compared to a solution containing free marker. Further, the oral administration of micelles in mice showed high area under curve of micellar paclitaxel (similar to the area of i.v. Taxol(®)), longer mean residence time (9-times longer than i.v. Taxol(®)) and high distribution volume (2-fold higher than i.v. Taxol(®)) indicating an efficient oral absorption of paclitaxel delivered by micelles. Intravenous administration of micelles also showed a significant improvement of pharmacokinetic parameters of micellar paclitaxel vs. Taxol(®), in particular higher area under curve (1.2-fold), 5-times longer mean residence time and lower clearance, indicating longer systemic circulation of the micelles.

Thermosensitive polymeric micelles for targeted drug delivery

Thermosensitive polymers are characterized by temperature-dependent aqueous solution properties. Below their lower critical solution temperature they are in an expanded state and fully dissolved, while above it they are dehydrated and insoluble. This has been exploited for the development of polymeric micelles that can be formed or destabilized depending on the solution temperature. Many micelle forming thermosensitive polymers have been described in literature, among which poly(N-isopropylacrylamide) (pNIPAAm), Pluronics (triblock copolymers of polypropylene oxide middle block flanked by two polyethylene oxide blocks) and poly(hydroxypropyl methacrylamide-lactate) (p(HPMAm-Lacn)) are the most frequently studied and some drug-loaded formulations based on thermosensitive polymers have reached clinical trials. The first generation of micelles composed of thermosensitive polymers was based on mere hydrophobic interactions between polymer blocks, while more recently shell or core crosslinking was introduced, in order to improve their stability in the circulation after intravenous administration and therefore, the accumulation of their depot in diseased areas. Various formulations of drug-loaded micelles based on thermosensitive polymers have shown promising results in vitro, as well as in vivo. This review gives an overview of the most important recent developments regarding the design and synthesis of various types of thermosensitve polymers for drug delivery.

Characterisation of different nanoparticles with a potential use for drug delivery in neuropsychiatric disorders

OBJECTIVES

Nanoparticles are promising tools for targeted delivery of drugs in the treatment of different diseases, including neuropsychiatric disorders. However, they need to be carefully characterised for any adverse effects which may occur in their presence. In this study, we evaluated the applicability of nanoparticles that belong to three different groups: (i) aggregates from amphiphilic diblock copolymers composed of poly(2-ethyl-2-oxazoline) (PEtOx) and poly(2-phenyl-2-oxazoline) (PPhOx) in different ratios, (ii) stabilised polymeric micelles (SPM) based on poly(ethylene oxide)-b-poly(propylene oxide)-bpoly(ethylene oxide) (PEO-PPO-PEO) and (iii) star-like polymer with poly(acrylic acid) arms and branched polystyrene interior (PSPAA).

METHODS

Using cultured human neural progenitor cells, we characterised six nanoparticles (POx-9, POx-23 and POx-46 - the polyoxazoline group, SPM-F38 and SPMMS - the SPM group, and PSPAA - the star-like polymer) for neurotoxicity and effect on neurodevelopmental genes. Nanoparticles ability to activate complement system in blood was assessed by ELISA.

RESULTS

None of the nanoparticles exhibited neurotoxicity. However, POx-9, POx-23, POx-46 and SPM-F38 activated complement system. POx-9 and SPM-F38 resulted in inhibition of expression of 19 and 26 out of 30 tested neurodevelopmental genes, respectively.

CONCLUSIONS

Considering the properties of the studied nanoparticles, only PSPAA and SPMMS can be used at high concentrations for drug delivery without compromising neurogenesis and neurodevelopment, and activation of complement system.

Characterization of Biomaterials by Soft X-Ray Spectromicroscopy

Synchrotron-based soft X-ray spectromicroscopy techniques are emerging as useful tools to characterize potentially biocompatible materials and to probe protein interactions with model biomaterial surfaces. Simultaneous quantitative chemical analysis of the near surface region of the candidate biomaterial, and adsorbed proteins, peptides or other biological species can be obtained at high spatial resolution via scanning transmission X-ray microscopy (STXM) and X-ray photoemission electron microscopy (X-PEEM). Both techniques use near-edge X-ray absorption fine structure (NEXAFS) spectral contrast for chemical identification and quantitation. The capabilities of STXM and X-PEEM for the analysis of biomaterials are reviewed and illustrated by three recent studies: (1) characterization of hydrophobic surfaces, including adsorption of fibrinogen (Fg) or human serum albumin (HSA) to hydrophobic polymeric thin films, (2) studies of HSA adsorption to biodegradable or potentially biocompatible polymers, and (3) studies of biomaterials under fully hydrated conditions. Other recent applications of STXM and X-PEEM to biomaterials are also reviewed.

Interaction of alpha-gliadin with polyanions: design considerations for sequestrants used in supportive treatment of celiac disease

Copolymers of sodium 4-styrene sulfonate (SS) and hydroxyethyl methacrylate (HEMA) were investigated as sequestrants of alpha-gliadin, a gluten protein, for the treatment of gluten intolerance. The interactions of alpha-gliadin with poly(SS) and poly(HEMA-co-SS) with 9 and 26 mol% SS content were studied at gastric (1.2) and intestinal (6.8) pH using circular dichroism and measurements of turbidity, dynamic light scattering and zeta potential. The interactions and their influence on alpha-gliadin secondary and aggregated structures depended mainly on the ratio of polymer negative and protein positive charges at pH 1.2, and on polymer SS content at polymer concentrations providing in excess of negative charges at either pH. Poly(SS) could not form complex particles with alpha-gliadin in a sufficient excess of negative charges. Copolymerization with HEMA enhanced the formation of complex particles. Poly(HEMA-co-SS) with intermediate SS content was found to be the most effective sequestrant for alpha-gliadin. This study provides insight into design considerations for polymer sequestrants used in the supportive treatment of celiac disease.

Supramolecular assemblies from amphiphilic homopolymers: Testing the scope

It has been shown by us in a recent communication that homopolymers, in which each repeat unit contains a hydrophilic and a hydrophobic head group, are capable of forming environment-dependent micellar or inverse micellar assemblies. A systematic structure-property relationship study is carried out here to test the scope of the design. We show here that the molecular design is indeed broadly applicable and that there is a significant gain in the critical aggregation concentrations of these polymers, as compared to the small molecule counterparts. We also show that the design can be tuned to achieve vesicle-type assemblies, which further expands the repertoire of amphiphilic homopolymers in a variety of areas. Characterizations of these assemblies have been carried out using transmission electron microscopy, dynamic light scattering, static light scattering, and dye incorporation experiments.