Catechol End-Functionalized Polylactide by Organocatalyzed Ring-Opening Polymerization

pH Effect on Particle Aggregation of Vanillin End-Capped Polylactides Bearing a Hydrophilic Group Connected by a Cyclic Acetal Moiety

To enhance the pH-responsiveness of poly(lactic acid) (PLA) particles, desired vanillin acetal-based initiators were synthesized and functional PLA was initiated at the chain end. PLLA-V6-OEG₃ particles were prepared using polymers with various M_n values of 2400-4800 g/mol. PLLA-V6-OEG₃ was appropriated to achieve a pH-responsive behavior under physiological conditions within 3 min via the six-membered ring diol-ketone acetal. Moreover, it was found that the polymer chain length (M_n) influenced the aggregation rate. TiO₂ was selected as the blending agent to improve the aggregation rate. The PLLA-V6-OEG₃ blended with TiO₂ was found to accelerate the aggregation rate compared with that without TiO₂, and the best ratio of polymer/TiO₂ was 1:1. To study the effect of the chain end for stereocomplex polylactide (SC-PLA) particles, PLLA-V6-OEG₄ and PDLA-V6-OEG₄ were successfully synthesized. The obtained results of SC-PLA particle aggregation implied that the types of chain end and the molecular weight of polymer could influence the aggregation rate. The SC-V6-OEG₄ blended with TiO₂ could not make our target to aggregate under physiological conditions within 3 min. This study motivated us to control the particle aggregation rate under physiological conditions for applying as a target drug carrier which is significantly influenced by not only the molecular weight but also the hydrophilicity of the chain-end as well as the number of acetal bonds.

Supercapacitor Performance of Magnetite Nanoparticles Enhanced by a Catecholate Dispersant: Experiment and Theory

The full potential of Fe₃O₄ for supercapacitor applications can be achieved by addressing challenges in colloidal fabrication of high active mass electrodes. Exceptional adsorption properties of catecholate-type 3,4-dihydroxybenzoic acid (DHBA) molecules are explored for surface modification of Fe₃O₄ nanoparticles to enhance their colloidal dispersion as verified by sedimentation test results and Fourier-transform infrared spectroscopy measurements. Electrodes prepared in the presence of DHBA show nearly double capacitance at slow charging rates as compared to the control samples without the dispersant or with benzoic acid as a non-catecholate dispersant. Such electrodes with active mass of 40 mg cm^-2 show a capacitance of 4.59 F cm^-2 from cyclic voltammetry data at a scan rate of 2 mV s^-1 and 4.72 F cm^-2 from galvanostatic charge-discharge data at a current density of 3 mA cm^-2. Experimental results are corroborated by density functional theory (DFT) analysis of adsorption behaviour of DHBA and benzoic acid at the (001) surface of Fe₃O₄. The strongest adsorption energy (ca. -1.8 eV per molecule) is due to the catechol group of DHBA. DFT analysis provides understanding of the basic mechanism of DHBA adsorption on the surface of nanoparticles and opens the way for fabrication of electrodes with high capacitance.

Synthesis of Novel One-Walled meso-Phenylboronic Acid-Functionalized Calix[4]pyrrole: A Highly Sensitive Electrochemical Sensor for Dopamine

Facile access to new one-walled meso-substituted phenylboronic acid-functionalized calix[4]pyrrole (C4P) has been revealed for the first time, starting from cost-effective and easily accessible materials. The structures of both the intermediate dipyrromethane (DPM) and the targeted functionalized C4P have been confirmed by means of ¹H-NMR, ¹³C-NMR, IR, and HRMS spectral data. The voltammetric investigations of the functionalized C4P films cast over a glassy carbon electrode (C4P-GCE) clearly establish the redox stability and redox accessibility of the boronic acid functional moiety present in the C4P framework. We demonstrate that the presence of the unique boronic acid functionality in the C4P endows it with an excellent potential for the highly sensitive electrochemical sensing of the neurotransmitter dopamine (DA). A linear correlation between the strength of the Faradaic signals corresponding to the electro-oxidation of DA over C4P-GCE and the concentration of DA was observed in a concentration range as wide as 0.165-2.302 μM. The C4P-GCE has revealed exceptional stability and reproducibility in the electrochemical sensing of DA, with a nanomolar level limit of detection as low as 15 nM.

Synthesis of Biomimetic Melanin-Like Multifunctional Nanoparticles for pH Responsive Magnetic Resonance Imaging and Photothermal Therapy

The design and development of multifunctional nanoparticles have attracted great interest in biomedical research. This study aims to prepare pH-responsive melanin-like nanoparticles for T1-weighted magnetic resonance imaging (MRI) and photothermal therapy. The new multifunctional nanoparticles (amino-Fe-PDANPs) are synthesized by copolymerization of dopamine and its derivative amino-N-[2-(diethylamino) ethyl]-3,4-dihydroxy-benzenepropanamide (N-Dopa) at room temperature. The size of nanoparticles can be controlled by NaOH concentration. The incorporation of N-Dopa is characterized by NMR and FT-IR. From transmission electron microscopy (TEM), the nanoparticles exhibit excellent dispersion stability in water and are spherical in shape. The MRI measurement has demonstrated that amino-Fe-PDANPs have a significant signal enhancement in responding to the acidic solution. Confirmed by the photothermal study, the nanoparticles exhibit a high photothermal conversion efficiency. The melanin-like multifunctional nanoparticles integrate both diagnosis and therapeutic functionalities, indicating the potential for theranostic application.

Functionalized Biodegradable Polymers via Termination of Ring-Opening Polymerization by Acyl Chlorides

Aliphatic polyesters are an important class of polymeric materials for biomedical applications due to their versatile and tunable chemistry, biocompatibility and biodegradability. A capability of direct bonding with biomedically significant molecules, provided by the presence of the reactive end functional groups (FGs), is highly desirable for prospective polymers. Among FGs, N-hydroxysuccinimidyl activated ester group (NHS) and maleimide fragment (MI) provide efficient covalent bonding with -NH- and -SH containing compounds. In our study, we found that NHS- and MI-derived acyl chlorides efficiently terminate living ring-opening polymerization of ε-caprolactone, L-lactide, ethyl ethylene phosphonate and ethyl ethylene phosphate, catalyzed by 2,6-di-tert-butyl-4-methylphenoxy magnesium complex, with a formation of NHS- and MI-functionalized polymers at a high yields. Reactivity of these polymers towards amine- and thiol-containing model substrates in organic and aqueous media was also studied.

Modular Functionalization of Laminarin to Create Value-Added Naturally Derived Macromolecules

With society's growing awareness of climate change, novel renewable and naturally sourced materials have received increasing attention as substitutes for petroleum-based products. Laminarin (LAM-OH) is a highly abundant, nontoxic, degradable polysaccharide found in marine organisms and hence is a promising sustainable polymeric candidate. This work reports on a simple, environmentally friendly, and customizable functionalization strategy for producing a toolbox of LAM-OH derivatives under mild conditions. Herein, natural-origin macromolecules exhibiting specific chemical moieties, namely, allyl, amine, carboxylic acid, thiol, aldehyde, and catechol, were prepared and chemically characterized. Furthermore, the obtained polymers were processed into cytocompatible hydrogels, obtained by employing distinct cross-linking mechanisms, to assess their potential for biomedical purposes. The application scope of such polymers could be extended to fields such as catalysis, cosmetics, life sciences, and food packaging, which can also benefit from having sustainable, nontoxic, and degradable materials. Moreover, it is anticipated that the methodology employed to create this library of new natural-based products could be adapted to modify other polysaccharides and biopolymers in general.