Biodegradable and pH-Responsive Amphiphilic Poly(succinimide) Derivatives for Triggered Release of Antibiotics for Management of Infected Wounds

Wound infection has become a healthy economic burden globally. Current wound management mainly relies on the use of antibiotics; however, the misuse and overuse of antibiotics can easily result in antibiotic resistance. This study proposes a biodegradable, biocompatible, and pH-responsive amphiphilic 11-aminoundecanoic acid-grafted polysuccinimide (AUA-PSI) as a nanocarrier for drug encapsulation via nanoprecipitation. The succinimide groups in the backbone of PSI allow facile postfunctionalization via an aminolysis reaction. The degree of substitution of AUA can be modulated to adjust the degradation rate, pH sensitivity, and drug-release profile. Antibiotic rifampicin was incorporated with AUA-PSI to form Rif-AUA-PSI nanoparticles and demonstrated pH-responsiveness and antimicrobial activity. Because of the elevation of the pH value from pH = ∼ 5.5 in healthy skin to pH > 7 in an infected wound, Rif-AUA-PSI nanoparticles begin to decompose and release Rif upon the hydrolysis of succinimide/amide and deprotonation of carboxyl groups. The effective suppression of bacterial growth by Rif-AUA-PSI nanoparticles was demonstrated using a plate count method. More importantly, Rif-AUA-PSI nanoparticles were physically deposited on cotton gauze bandages as an antibiotic wound dressing. The Rif-AUA-PSI-modified gauze was applied to infected wounds on rats for wound management. The results show fast wound healing and inhibition of bacterial growth, which demonstrate that the method promotes modulable amphiphilicity, biodegradability, biocompatibility, pH-responsiveness, and facile modification for nanomedicine and medical devices.

Synthesis of polyaspartic acid-capped 2-aminoethylamino acid as a green water treatment agent and study of its inhibition performance and mechanism for calcium scales

Polyaspartic acid (PASP), a well-known green scale inhibitor for industrial water treatment, might be decomposed with prolonged duration, and its anti-scaling performance against CaCO₃ and CaSO₄ is diminished at a low concentration (<10 mg L⁻¹) and a high temperature. With semi-ethylenediaminetetraacetic acid (EDTA) tetrasodium salt as the mimicking model, novel phosphorus-free PASP-capped 2-aminoethylamino acid (PASP–ED₂A) containing side chains bearing multi-functional groups is rationally designed and successfully prepared via the ring-opening reaction of cheap poly(succinimide) under mild reaction conditions with the assistance of readily available 2-aminoethyl amino acid. The static scale inhibition method is used to evaluate the scale inhibition performance of the as-synthesized PASP derivative. Scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy are utilized to monitor the crystallization process of calcium carbonate and calcium sulfate scales, and density functional theory calculations are conducted to shed light on the relationship between the molecular structure and scale inhibition mechanism of PASP–ED₂A. Results show that the as-prepared PASP–ED₂A shows better scale inhibition performance for CaCO₃ and CaSO₄ than PASP with a low concentration, a high temperature, and an extended duration. Particularly, PASP–ED₂A with a concentration of 10 mg L⁻¹ exhibits the best scale inhibition performance for CaCO₃; its scale inhibition capacity is about two times as much as that of PASP. The reason lies in that the coordination atoms in the molecular structure of PASP–ED₂A can chelate with Ca²⁺ to inhibit the combination of Ca²⁺ with anions and prevent the generation of CaCO₃ and CaSO₄ scales. The PASP–ED₂A derivative can more efficiently retard the formation and growth of CaCO₃ and CaSO₄ crystal nuclei and exerts better inhibition performance against CaCO₃ and CaSO₄ scales than PASP.

A novel phosphorus-free PASP–ED₂A antiscalant exhibits good scale inhibition performance against calcium scale at a low concentration or a high temperature, better than that of PASP.

Design of an Amphiphilic Poly(aspartamide)-mediated Self-assembled Nanoconstruct for Long-Term Tumor Targeting and Bioimaging

Biodegradable polymers have been developed for the targeted delivery of therapeutics to tumors. However, tumor targeting and imaging are usually limited by systemic clearance and non-specific adsorption. In this study, we used poly(amino acid) derivatives, such as poly(succinimide), to synthesize a nanomicelle-forming poly(hydroxyethylaspartamide) (PHEA, P) modified sequentially with octadecylamine, polyethylene glycol (PEG, P), and glycine (G) to design PHEA-PEG-glycine (PPG) nanoparticles (NPs). These PPG NPs were further tethered to cyclic Arg-Gly-Asp (cRGD) sequences for formulating tumor-targeting PPG-cRGD NPs, and then loaded with IR-780 dye (PPG-cRGD-IR-780) for visualizing tumor homing. cRGD cloaked in PPG NPs could bind specifically to both tumor endothelium and cancer cells overexpressing α_vβ₃ integrins. PPG-cRGD NPs exhibited enhanced physiological stability, cellular viability, and targeted intracellular uptake in cancer cells. In addition, PPG-cRGD NPs offered enhanced systemic circulation, leading to preferential tumor targeting and prolonged fluorescence tumor imaging for nearly 30 days. Nevertheless, non-targeted formulations demonstrated premature systemic clearance with short-term tumor imaging. Histochemical analysis showed no damage to normal organs, reaffirming the biocompatibility of PHEA polymers. Overall, our results indicated that PPG-cRGD NPs, which were manipulated to obtain optimal particle size and surface charge, and were complemented with tumor targeting, could improve the targeted and theranostic potential of therapeutic delivery.

CO2-Triggered and temperature-switchable crystallization-driven self-assembly of a semicrystalline block copolymer in aqueous medium

The synthesis of a semicrystalline block copolymer comprising a hydrophilic poly(acrylic acid) pure block and an amphiphilic poly(acrylic acid)-r-poly(octadecyl acrylate) random block by nitroxide-mediated polymerization is reported.

Polyaspartamide-based graft copolymers encapsulating iron oxide nanoparticles for imaging and fluorescence labelling of immune cells

Iron oxide nanoparticles (NPs) were encapsulated with polyaspartamide-based graft copolymers to bind and track the immune cells as imaging probes. Mono-disperse iron oxide NPs with a mean diameter of 10.7 nm were synthesized by the thermal decomposition method, and their shape and distribution were measured by electrophoretic light scattering and transmission electron microscopy. To enhance their biocompatibility, interfacial and hydrodynamic stability, and fluorescence detection, biodegradable polysuccinimide (PSI) grafted with several functional groups of octadecylamine (C18), ethanolamine (EA), ethylenediamine (EDA), 4-(N-maleimidomethyl) cyclohexane carboxylic acid N-hydroxysuccinimide ester (SMCC), and fluorescein isothiocyanate (FITC) was coated on the iron oxide NPs. The structure of the C18/EA/SMCC/FITC-g-PSI copolymer was confirmed using ¹H-NMR and FTIR spectroscopy, and its cell binding ability was investigated by flow cytometry and confocal laser scanning microscopy. The synthesized C18/EA/SMCC/FITC-g-PSI copolymer showed an excellent binding affinity to CD4+ T cells, and was highly biocompatible as the cell viability at the highest polymer concentration of 0.4 mg mL^-1 was greater than 85 and 75% after 24 and 48 h, respectively, from MTT assay.

Structural Characterization of Biocompatible Reverse Micelles Using Small-Angle X-ray Scattering, 31P Nuclear Magnetic Resonance, and Fluorescence Spectroscopy

The most critical problem regarding the use of reverse micelles (RMs) in several fields is the toxicity of their partial components. In this sense, many efforts have been made to characterize nontoxic RM formulations on the basis of biological amphiphiles and/or different oils. In this contribution, the microstructure of biocompatible mixed RMs formulated by sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT) and tri- n-octylphosphine oxide (TOPO) surfactants dispersed in the friendly solvent methyl laurate was studied by using SAXS and ³¹P NMR and by following the solvatochromic behavior of the molecular probe 4-aminophthalimide (4-AP). The results indicated the presence of RM aggregates upon TOPO incorporation with a droplet size reduction and an increase in the interfacial fluidity in comparison with pure AOT RMs. When confined inside the mixed systems, 4-AP showed a red-edge excitation shift and confirmed the increment of interfacial fluidity upon TOPO addition. Also, the partition between the external nonpolar solvent and the RM interface and an increase in both the local micropolarity and the capability to form a hydrogen bond interaction between 4-AP and a mixed interface were observed. The findings have been explained in terms of the nonionic surfactant structure and its complexing nature expressed at the interfacial level. Notably, we show how two different approaches, i.e., SAXS and the solvatochromism of the probe 4-AP, can be used in a complementary way to enhance our understanding of the interfacial fluidity of RMs, a parameter that is difficult to measure directly.

Construction of micelles based on biocompatible pseudo-graft polymers via β-cyclodextrin/cholesterol interaction for protein delivery

A pseudo-graft copolymer micelle was constructed from the self-assembly of (6-(2-aminoethyl)-amino-6-deoxy)-cyclodextrin (β-CDen)-modified poly(aspartic acid) (PASP-CD) with cholesterol-modified poly(d,l-lactide) (PLA-Chol) using host–guest inclusion complexation in water.