Biological properties of novel polysuccinimide derivatives synthesized via quaternary ammonium grafting

Facile fabrication of temperature/pH dual sensitive hydrogels based on cellulose and polysuccinimide through aqueous amino-succinimide reaction

A temperature/pH dual sensitive hydrogel with a semi-interpenetrating network (semi-IPN) structure was synthesized through an aqueous amino-succinimide reaction between water-soluble polysuccinimide and polyethyleneimine in the presence of thermosensitive cellulose derivatives. Single-factor experiments were carried out to optimize the preparation conditions of the semi-IPN hydrogel. The swelling behavior and cytotoxicity assay of the hydrogel were tested. Finally, taking 5- fluorouracil (5-Fu) as a model drug, the release performance of the 5-Fu-loaded hydrogel was investigated. The results indicated that the swelling ratio (SR) first decreased and then increased when the pH of the solutions ascended from 2 to 10. The SR decreased with the increase in temperature. In addition, the swelling behavior of the hydrogel was reversible and reproducible under different pH values and temperatures. The prepared hydrogels had good cytocompatibility. The release behavior of 5-Fu was most consistent with the Korsmeyer-Peppas model and followed the case II diffusion. The acidic environment was beneficial for the release of 5-Fu. The preparation process of the semi-IPN hydrogel is simple and the reaction can proceed quickly in water. The strategy introduced here has great potential for application in the preparation of drug carriers.

A Pyr-loaded polymer microparticle for effectively controlling Solenopsis invicta (Hymenoptera: Formicidae) in the nest

Human interference and incorrect use of pesticides are easy to induce red imported fire ant (RIFA) escape and migrate from a nest, resulting in ineffective control of RIFA. In order to avoid RIFA alert, we designed an amphiphilic PSI-mPEG-Boc-DAH loaded Pyr to make the microparticles with effective controlled release. The investigation showed that the quantity of Pyr released by Pyr@PSI-mPEG-Boc-DAH under acidic environment was only 36.40 ± 1.90% at 48 h, whereas the release rate of original Pyr was 75.23 ± 5.71%. And the RIFA mortality rate of 1 ppm Pyr in Pyr@PSI-mPEG-Boc-DAH microparticles at 48 h was only 7.78%, which was significantly lower than that of the Pyr (47.78%). Futhermore, the death rate increased sharply after 48 h, and reached 95.84% within a week after using Pyr@PSI-mPEG-Boc-DAH microparticles. Moreover, PSI-mPEG-Boc-DAH carriers could be absorbed and even transported to crop of the RIFA for subsequent trophallaxis by using fluorescence tracking. In the field experiment, the reduction rate of Pyr@PSI-mPEG-Boc-DAH treatment was achieved 99.89% after 7 d. Pyr@PSI-mPEG-Boc-DAH didn't cause RIFA to be alarmed within 48 h and could kill nearly all of ants in the nest after 7 d, which showed a very good control effect in the field experiment. This work provided a new idea and guidance for the effective control RIFA and the development of sustainable agriculture.

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.

Tuning the Endocytosis of Hybrid Micelles through Spatial Regulation of Cationic Groups

The ability of nanocarriers to enter tumor cells can be enhanced by positive surface charge. Nonetheless, the relationship between the spatial distributions of cationic groups and the endocytosis and tumor penetration of nanocarriers remains largely elusive. Here, using quaternary ammonium salt (QAS) as a model cationic group, a series of hybrid micelles (HMs) bearing QAS with different spatial distributions were prepared from star-shaped polymers with well-defined molecular architectures. The structural characteristics of HM, such as spatial location of QAS and local poly(ethylene glycol) (PEG) density near QAS, were investigated by both experimental techniques and dissipative particle dynamics (DPD) simulation. We show that the drug carriers with QAS extending to the micellar outer space allows QAS to facilitate cell surface binding with minimized hindrance, resulting in greatly enhanced endocytosis compared with nanocarriers with QAS attached onto the micellar surface or shielded by a PEG corona. This study offers cues for future development of tumor-penetrating drug delivery systems.

Characterization of a conjugated polysuccinimide-carboplatin compound

Carboplatin, an advanced anticancer drug with excellent efficacy against ovarian cancer, was developed to alleviate the side effects that often occur with cisplatin and other platinum-based compounds. Our study reports the in vitro characteristics, viability, and activity of cells expressing the inducible nitric oxide synthase (iNOS) gene after carboplatin was conjugated with polysuccinimide (PSI) and administered in combination with other widely used anticancer drugs. PSI, which has promising properties as a drug delivery material, could provide a platform for prolonging carboplatin release, regulating its dosage, and improving its side effects. The iNOS gene has been shown to play an important role in both cancer cell survival and inhibition. Herein, we synthesized a PSI-carboplatin conjugate to create a modified anticancer agent and confirmed its successful conjugation. To ensure its solubility in water, we further modified the structure of the PSI-carboplatin conjugate with 2-aminoethanol groups. To validate its biological characteristics, the ovarian cancer cell line SKOV-3 and normal ovarian Chinese hamster ovary cells were treated with the PSI-carboplatin conjugate alone and in combination with paclitaxel and topotecan, both of which are used in conventional chemotherapy. Notably, PSI-carboplatin conjugation can be used to predict changes in the genes involved in cancer growth and inhibition. In conclusion, combination treatment with the newly synthesized polymer-carboplatin conjugate and paclitaxel displayed anticancer activity against ovarian cancer cells but was not toxic to normal ovarian cancer cells, resulting in the development of an effective candidate anticancer drug without severe side effects.

Self-healable nanocellulose composite hydrogels combining multiple dynamic bonds for drug delivery

Herein, we developed two nanocomposite polysaccharide hydrogels TPP-CNC and TPP-CNF via simple mixing method, which were constructed with multiple dynamic bonds. The microstructural features, mechanical properties, rheological properties, healable ability and biocompatibility of the complex hydrogels were evaluated. The TPP-CNC and TPP-CNF complex hydrogels exhibited higher tensile strength than pure polysaccharide hydrogel, from ~259 KPa to ~890 KPa and ~910 KPa, respectively, that was attributed to the contribution of ionic crosslinked network and hydrogen bonds. In addition, the hydrogels indicated superior fatigue resistance and high energy dissipation ratio during loading-unloading tests because of the physical sacrifice bonds, which also decreased the self-healing time at room temperature (~15 min). More importantly, the drug loaded nanocomposite hydrogels showed sustained release, reduction burst release, increased release under acidic environment, and the drug release kinetics belonged to Fickian diffusion mechanism. Therefore, the nanocellulose polysaccharide hydrogels have the highly promising to explore as biomaterials for drug delivery.

Preparation of p-amino salicylic acid-modified polysuccinimide as water-based nanocarriers for enhancing pesticide stability and insecticidal activity

Avermectin (AVM) is a biopesticide with low toxicity and high activity, but has limited use due to its poor water solubility and easy decomposition. A delivery system that can stabilize this biopesticide can play a significant role for improving its biological activity. Herein, water-dispersible functionalized polysuccinimide nanoparticles (PAD) were prepared by a ring-opening reaction and subsequently used to encapsulate AVM via self-assembly to form AVM@PAD nanoparticles with a loading ratio of 10.04 %. The half-life under UV radiation (300 W) of AVM@PAD was three times higher than that of free AVM, demonstrating the excellent protective ability of PAD. In addition, AVM@PAD nanoparticles could sustain the release of AVM for 70 h with a cumulative release rate of 70 %. AVM@PAD nanoparticles also showed a pH-responsive release, and their maximum cumulative release rate was at neutral pH. Moreover, the median lethal concentration (LC₅₀) value of AVM@PAD with respect to Plutella xylostella was 34.50 mg/L, while that of free AVM was 56.05 mg/L. These results showed that the AVM@PAD nanoparticles can potentially and effectively promote drug stability and biological activity in agriculture.

Preparation, characterization, and antibacterial property of carboxymethyl cellulose derivatives bearing tetrabutylammonium salt

Carboxymethyl cellulose derivatives bearing tetrabutylammonium moieties (CMC-TBA) were synthesized by the acidification of carboxymethyl cellulose (CMC) followed by acid-base neutralization with tetrabutylammonium hydroxide. The products were identified by Fourier transform infrared (FT-IR), ¹H nuclear magnetic resonance (NMR) spectroscopy and the degrees of substitution (DS) values were also quantified according to the integral area values in ¹H NMR spectra. It was revealed that DS values had a positive relationship with the molar ratios of TBAOH to CMC. The antibacterial behaviors against gram-positive bacteria S. aureus and gram-negative bacteria E. coli were investigated using serial two-fold dilution method (MIC and MBC) and the disc diffusion method (inhibition zone). The results showed that comparison with CMC, all new CMC-TBA derivatives exhibited high antibacterial activity that depends on bacteria type and their degrees of cationization. The antibacterial action was more effective against S. aureus than E. coli, which could be attributed to the fact that the latter has a complicated bilayer structure of cell wall. Besides, an apparent tendency that the antibacterial activity of CMC-TBA derivatives enhanced with an increase in the degrees of cationization was found. This work suggests that these new derivatives can be introduced as efficient antibacterial biomaterials for biomedical purposes.