Thermoresponsive Polymer-Antibiotic Conjugates Based on Gradient Copolymers of 2-Oxazoline and 2-Oxazine

Modification of Welan gum with poly(2-oxazoline) to obtain thermoviscosifying polymer for enhanced oil recovery

Thermoviscosifying polymers refer to a category of smart materials that exhibit a responsive behavior to environmental stimuli, specifically demonstrating a natural rise in viscosity of solutions as the temperature increases. The temperature-dependent behavior exhibited by thermally viscous polymers renders them potentially advantageous in the context of Enhanced Oil Recovery (EOR). There exists a dearth of research pertaining to the application of thermoviscosifying polymer for better recovery in reservoirs characterized by high temperatures and high salt content. In order to tackle the mentioned concerns, this study examined the utilization of welan gum modified with poly(2-oxazoline) as thermally responsive chain segments to enhance viscosity. The objective was to evaluate the ability to enhance viscosity under thermal conditions and to assess their effectiveness in displacement of reservoir oil in high temperature and high salt environments. This study aimed to establish a theoretical framework for understanding the correlation between the molecular structure and performance of novel thermally viscous polymers. Additionally, it sought to offer practical insights into designing the molecular structure of thermally viscous polymers suitable for polymer flooding in high temperature and high salt environments. Furthermore, the study proposed the application of these new thermoviscosifying polymers for EOR.

Schiff-Base Cross-Linked Poly(2-oxazoline) Micelle Drug Conjugates Possess Antiferroptosis Activity in Numerous In Vitro Cell Models

A great deal of nanocarriers have been applied to induce ferroptosis in cancer research, yet there are limited examples of nanocarrier formulations to rescue ferroptosis, which can be applied to neurodegeneration, inflammation, liver damage, kidney disease, and more. Here, we present the synthesis, characterization, and in vitro evaluation of pH-responsive, core-cross-linked micelle (CCM) ferrostatin-1 (Fer-1) conjugates with amine, valproic acid, and biotin surface chemistries. Fer-1 release from stable and defined CCM Fer-1 conjugates was quantified, highlighting the sustained release for 24 h. CCM Fer-1 conjugates demonstrated excellent ferroptosis rescue by their antilipid peroxidation activity in a diverse set of cell lines in vitro. Additionally, CCMs showed tunable cell association in SH-SY5Y and translocation across an in vitro blood-brain barrier (BBB) model, highlighting potential brain disease applications. Overall, here, we present a polymeric Fer-1 delivery system to enhance Fer-1 action, which could help in improving Fer-1 action in the treatment of ferroptosis-related diseases.

Evaluation of Doxorubicin-loaded Echogenic Macroemulsion for Targeted Drug Delivery

BACKGROUND

The latest technology trend in targeted drug delivery highlights stimuliresponsive particles that can release an anticancer drug in a solid tumor by responding to external stimuli.

OBJECTIVE

This study aims to design, fabricate, and evaluate an ultrasound-responsive drug delivery vehicle for an ultrasound-mediated drug delivery system.

METHODS

The drug-containing echogenic macroemulsion (eME) was fabricated by an emulsification method using the three phases (aqueous lipid solution as a shell, doxorubicin (DOX) contained oil, and perfluorohexane (PFH) as an ultrasound-responsive agent). The morphological structure of eMEs was investigated using fluorescence microscopy, and the size distribution was analyzed by using DLS. The echogenicity of eME was measured using a contrast-enhanced ultrasound device. The cytotoxicity was evaluated using a breast cancer cell (MDA-MB-231) via an in vitro cell experiment.

RESULTS

The obtained eME showed an ideal morphological structure that contained both DOX and PFH in a single particle and indicated a suitable size for enhancing ultrasound response and avoiding complications in the blood vessel. The echogenicity of eME was demonstrated via an in vitro experiment, with results showcasing the potential for targeted drug delivery. Compared to free DOX, enhanced cytotoxicity and improved drug delivery efficiency in a cancer cell were proven by using DOX-loaded eMEs and ultrasound.

CONCLUSION

This study established a platform technology to fabricate the ultrasound-responsive vehicle. The designed drug-loaded eME could be a promising platform with ultrasound technology for targeted drug delivery.

Mechanism of Action of Oxazoline-Based Antimicrobial Polymers Against Staphylococcus aureus: In Vivo Antimicrobial Activity Evaluation

Antimicrobial-resistant pathogens have reached alarming levels, becoming one of the most pressing global health issues. Hence, new treatments are necessary for the fight against antimicrobial resistance. Synthetic nanoengineered antimicrobial polymers (SNAPs) have emerged as a promising alternative to antimicrobial peptides, overcoming some of their limitations while keeping their key features. Herein, a library of amphiphilic oxazoline-based SNAPs using cationic ring-opening polymerization (CROP) is designed. Amphipathic compounds with 70% cationic content exhibit the highest activity against clinically relevant Staphylococcus aureus isolates, maintaining good biocompatibility in vitro and in vivo. The mechanism of action of the lead compounds against S. aureus is assessed using various microscopy techniques, indicating cell membrane disruption, while the cell wall remains unaffected. Furthermore, a potential interaction of the compounds with bacterial DNA is shown, with possible implications on bacterial division. Finally, one of the compounds exhibits high efficacy in vivo in an insect infection model.

Non-activated Esters as Reactive Handles in Direct Post-Polymerization Modification

Non-activated esters are prominently featured functional groups in polymer science, as ester functional monomers display great structural diversity and excellent compatibility with a wide range of polymerization mechanisms. Yet, their direct use as a reactive handle in post-polymerization modification has been typically avoided due to their low reactivity, which impairs the quantitative conversion typically desired in post-polymerization modification reactions. While activated ester approaches are a well-established alternative, the modification of non-activated esters remains a synthetic and economically valuable opportunity. In this review, we discuss past and recent efforts in the utilization of non-activated ester groups as a reactive handle to facilitate transesterification and aminolysis/amidation reactions, and the potential of the developed methodologies in the context of macromolecular engineering.

Convenient and Controllable Synthesis of Poly(2-oxazoline)-Conjugated Doxorubicin for Regulating Anti-Tumor Selectivity

Polyethylene glycol (PEG)-doxorubicin (DOX) conjugation is an important strategy to improve toxicity and enhance clinically therapeutic efficacy. However, with the frequent use of PEG-modified drugs, the accumulation of anti-PEG antibodies has become a tough issue, which limits the application of PEG-drug conjugation. As an alternative solution, poly(2-oxazoline) (POX)-DOX conjugation has shown great potential in the anti-tumor field, but the reported conjugation process of POX with DOX has drawbacks such as complex synthetic steps and purification. Herein, we propose a convenient and controllable strategy for the synthesis of POX-DOX conjugation with different chain lengths and narrow dispersity by N-boc-2-bromoacetohydrazide-initiated 2-ethyl-oxazoline polymerization and the subsequent deprotection of the N-Boc group and direct reaction with DOX. The DOX-PEtOx conjugates were firstly purified, and the successful conjugations were confirmed through various characterization methods. The synthetic DOX-PEtOx_n conjugates reduce the toxicity of DOX and increase the selectivity to tumor cells, reflecting the promising application of this POX-DOX conjugation strategy in drug modification and development.

Polytrimethylenimines: Highly Potent Antibacterial Agents with Activity and Toxicity Modulated by the Polymer Molecular Weight

Cationic polymers have been extensively investigated as a potential replacement for traditional antibiotics. Here, we examined the effect of molecular weight (MW) on the antimicrobial, cytotoxic, and hemolytic activity of linear polytrimethylenimine (L-PTMI). The results indicate that the biological activity of the polymer sharply increases as MW increases. Thanks to a different position of the antibacterial activity and toxicity thresholds, tuning the MW of PTMI allows one to achieve a therapeutic window between antimicrobial activity and toxicity concentrations. L-PTMI presents significantly higher antimicrobial activity against model microorganisms than linear polyethylenimine (L-PEI) when polymers with a similar number of repeating units are compared. For the derivatives of L-PTMI and L-PEI, obtained through N-monomethylation and partial N,N-dimethylation of linear polyamines, the antimicrobial activity and toxicity were both reduced; however, resulting selectivity indices were higher. Selected materials were tested against clinical isolates of pathogens from the ESKAPE group and Mycobacteria, revealing good antibacterial properties of L-PTMI against antibiotic-resistant strains of Gram-positive and Gram-negative bacteria but limited antibacterial properties against Mycobacteria.

Antimicrobial Activity Enhancers: Towards Smart Delivery of Antimicrobial Agents

The development of effective treatments against infectious diseases is an extensive and ongoing process due to the rapid adaptation of bacteria to antibiotic-based therapies. However, appropriately designed activity enhancers, including antibiotic delivery systems, can increase the effectiveness of current antibiotics, overcoming antimicrobial resistance and decreasing the chance of contributing to further bacterial resistance. The activity/delivery enhancers improve drug absorption, allow targeted antibiotic delivery, improve their tissue and biofilm penetration and reduce side effects. This review provides insights into various antibiotic activity enhancers, including polymer, lipid, and silver-based systems, designed to reduce the adverse effects of antibiotics and improve formulation stability and efficacy against multidrug-resistant bacteria.