Antibacterial Gelatin Composite Hydrogels Comprised of In Situ Formed Zinc Oxide Nanoparticles.

We report the feasibility of using gelatin hydrogel networks as the host for the in situ, environmentally friendly formation of well-dispersed zinc oxide nanoparticles (ZnONPs) and the evaluation of the antibacterial activity of the as-prepared composite hydrogels. The resulting composite hydrogels displayed remarkable biocompatibility and antibacterial activity as compared to those in previous studies, primarily attributed to the uniform distribution of the ZnONPs with sizes smaller than 15 nm within the hydrogel network. In addition, the composite hydrogels exhibited better thermal stability and mechanical properties as well as lower swelling ratios compared to the unloaded counterpart, which could be attributed to the non-covalent interactions between the in situ formed ZnONPs and polypeptide chains. The presence of ZnONPs contributed to the disruption of bacterial cell membranes, the alteration of DNA molecules, and the subsequent release of reactive oxygen species within the bacterial cells. This chain of events culminated in bacterial cell lysis and DNA fragmentation. This research underscores the potential benefits of incorporating antibacterial agents into hydrogels and highlights the significance of preparing antimicrobial agents within gel networks.

Incorporation of Glutamic Acid or Amino-Protected Glutamic Acid into Poly(Glycerol Sebacate): Synthesis and Characterization.

Poly(glycerol sebacate) (PGS), a soft, tough elastomer with excellent biocompatibility, has been exploited successfully in many tissue engineering applications. Although tunable to some extent, the rapid in vivo degradation kinetics of PGS is not compatible with the healing rate of some tissues. The incorporation of L-glutamic acid into a PGS network with an aim to retard the degradation rate of PGS through the formation of peptide bonds was conducted in this study. A series of poly(glycerol sebacate glutamate) (PGSE) containing various molar ratios of sebacic acid/L-glutamic acid were synthesized. Two kinds of amino-protected glutamic acids, Boc-L-glutamic acid and Z-L-glutamic acid were used to prepare controls that consist of no peptide bonds, denoted as PGSE-B and PGSE-Z, respectively. The prepolymers were characterized using 1H-NMR spectroscopy. Cured elastomers were characterized using FT-IR, DSC, TGA, mechanical testing, and contact angle measurement. In vitro enzymatic degradation of PGSE over a period of 28 days was investigated. FT-IR spectroscopy confirmed the formation of peptide bonds. The glass transition temperature for the elastomer was found to increase as the ratio of sebacic acid/glutamic acid was increased to four. The decomposition temperature of the elastomer decreased as the amount of glutamic acid was increased. PGSE exhibited less stiffness and larger elongation at break as the ratio of sebacic acid/glutamic acid was decreased. Notably, PGSE-Z was stiffer and had smaller elongation at break than PGSE and PGSE-B at the same molar ratio of monomers. The results of in vitro enzymatic degradation demonstrated that PGSE has a lower degradation rate than does PGS, whereas PGSE-B and PGSE-Z degrade at a greater rate than does PGS. SEM images suggest that the degradation of these crosslinked elastomers is due to surface erosion. The cytocompatibility of PGSE was considered acceptable although slightly lower than that of PGS. The altered mechanical properties and retarded degradation kinetics for PGSE reflect the influence of peptide bonds formed by the introduction of L-glutamic acid. PGSE displaying a lower degradation rate compared to that for PGS can be used as a scaffold material for the repair or regeneration of tissues that are featured by a low healing rate.

ZnO-loaded DNA nanogels as neutrophil extracellular trap-like structures in the treatment of mouse peritonitis.

Neutrophil extracellular traps (NETs) are chromatin-based structures that are released from neutrophils during infections and prevent microbes from spreading in the body through efficient degradation of their composition. Based on this chromatin-driven strategy of capturing and killing bacteria, we designed NET-like structures using DNA and ZnO nanoparticles (NPs). DNA was first purified from kiwifruit and treated with HCl to increase hydroxyl groups in the opened-deoxylribose form. The carboxyl groups of citric acid were then thermally crosslinked with said hydroxyl and primary amine groups in DNA, forming DNA-HCl nanogels (NGs). ZnO NPs were then used as positively charged granule enzymes, adsorbed onto the DNA-HCl NG, obtaining ZnO/DNA-HCl NGs (with NET biomimicry). In an anti-inflammatory assay, ZnO/DNA-HCl NGs significantly inhibited TNF-α, IL-6, iNOS and COX-2 expression in LPS-stimulated Raw264.7 cells. Moreover, the ZnO/DNA-HCl NGs markedly alleviated clinical symptoms in LPS-induced mouse peritonitis. Finally, ZnO/DNA-HCl NGs suppressed E. coli from entering circulation in septic mice while prolonging their survival. Our results suggest that the ZnO/DNA-HCl NGs, which mimic NET-like structures in the blocking of bacteria-inducted inflammation, may be a potential therapeutic strategy for bacterial infections.

Peptide Fibrillar Assemblies Exhibit Membranolytic Effects and Antimetastatic Activity on Lung Cancer Cells.

Cancer metastasis is a central oncology concern that worsens patient conditions and increases mortality in a short period of time. During metastatic events, mitochondria undergo specific physiological alterations that have emerged as notable therapeutic targets to counter cancer progression. In this study, we use drug-free, cationic peptide fibrillar assemblies (PFAs) formed by poly(L-Lysine)-block-poly(L-Threonine) (Lys-b-Thr) to target mitochondria. These PFAs interact with cellular and mitochondrial membranes via electrostatic interactions, resulting in membranolysis. Charge repulsion and hydrogen-bonding interactions exerted by Lys and Thr segments dictate the packing of the peptides and enable the PFAs to display enhanced membranolytic activity toward cancer cells. Cytochrome c (cyt c), endonuclease G, and apoptosis-inducing factor were released from mitochondria after treatment of lung cancer cells, subsequently inducing caspase-dependent and caspase-independent apoptotic pathways. A metastatic xenograft mouse model was used to show how the PFAs significantly suppressed lung metastasis and inhibited tumor growth, while avoiding significant body weight loss and mortality. Antimetastatic activities of PFAs are also demonstrated by in vitro inhibition of lung cancer cell migration and clonogenesis. Our results imply that the cationic PFAs achieved the intended and targeted mitochondrial damage, providing an efficient antimetastatic therapy.

Antibacterial polypeptide/heparin composite hydrogels carrying growth factor for wound healing.

We report an efficient growth factor delivering system based on polypeptide/heparin composite hydrogels for wound healing application. Linear and star-shaped poly(l-lysine) (l-PLL and s-PLL) were chosen due to not only their cationic characteristics, facilitating the efficient complexation of negatively charged heparin, but also the ease to tune the physical and mechanical properties of as-prepared hydrogels simply by varying polypeptide topology and chain length. The results showed that polymer topology can be an additional parameter to tune hydrogel properties. Our experimental data showed that these composite hydrogels exhibited low hemolytic activity and good cell compatibility as well as excellent antibacterial activity, making them ideal as wound dressing materials. Unlike other heparin-based hydrogels, these composite hydrogels with heparin densely deposited on the surface can increase the stabilization and concentration of growth factor, which can facilitate the healing process as confirmed by our in vivo animal model. We believe that these PLL/heparin composite hydrogels are promising wound dressing materials and may have potential applications in other biomedical fields.

In situ formation of silver nanoparticles-contained gelatin-PEG-dopamine hydrogels via enzymatic cross-linking reaction for improved antibacterial activities.

Hydrogels containing silver nanoparticles (AgNPs) were recently found to exhibit excellent antibacterial properties against both gram-negative/positive bacteria and fungi. In this study, we reported the synthesis of AgNPs-contained gelatin-polyethylene glycol-dopamine (AgNP-GPD) hydrogels via the in situ formation of AgNPs in GPD polypeptide solution, followed by an enzymatic cross-linking reaction to form hydrogels. The experimental results showed that the reducing reaction exerted by GPD polypeptides under physiological conditions can afford the formation of AgNPs in situ in the polypeptide solution without the need for additional reducing agents and/or processes such as UV or thermal treatments and then the hydrogelation of GPD polypeptide solution containing AgNPs were preceeded via enzymatic cross-linking reaction. It was found that the gelation time, hydrogel mechanical property, degree of swelling and degree of enzymatic degradation for both GPD and AgNP-GPD hydrogels can be tuned by varying enzyme/oxidative agent concentration, catechol content, and reducing reaction conditions such as reaction time and silver ion concentration. Importantly, AgNP-GPD hydrogels exhibit excellent antibacterial properties against gram-negative and gram-positive bacteria. This type of hydrogel is a promising biomaterial for biomedical applications including wound healing and tissue engineering.

[Brain developmental diseases and pathogenic mechanisms].

Development of the human brain is a strictly complex and precisely regulated process. Brain development includes the proliferation and differentiation of neural progenitor cells, migration and maturation of neurons, myelination of neuronal axons, synaptogenesis and organization of the neural circuits. Abnormalities of these developmental processes can lead to severe malformation and dysfunction of the brain, which may result in brain developmental diseases which have a high medical burden and have attracted global attention. Brain developmental diseases are typically divided into two categories according to abnormal brain morphology and dysfunction: malformation of cortical development (MCD) and neuropsychopathy. Microcephaly and autism spectrum disorder (ASD) are representative disorders of MCD and neuropsychopathy respectively. In this review, we summarize the progresses of these two typical and relevant brain developmental diseases including the mechanism and etiology of their development, gene expression, symptoms, and related to provide theoretical guidance for basic research and management and treatment.

TRAIL encapsulated to polypeptide-crosslinked nanogel exhibits increased anti-inflammatory activities in Klebsiella pneumoniae-induced sepsis treatment.

Bacterial infections are often treated inadequately. Sepsis, being one of its most severe forms, is a multi-layered, life-threatening syndrome induced by rampant immune responses, like cytokine storms, that leads to high morbidity and death of infected patients. Particularly, the current increment in resistant bacterial strains and the lack of creative antibiotics to counter such menace are central reasons to the worsening of the situation. To avoid the said crisis, the antimicrobial peptides (AMPs) were used to target cell wall components, such as lipopolysaccharides (LPS), seems to have the most promise. These combine the ability of broad-spectrum bactericidal activity with low potential for induction of resistance. Inhibition of cytokine storms induced by activated immune cells has been considered a feasible treatment for in sepsis. One of the therapeutic approaches widely utilized in inducing apoptosis in inflammatory cells is the use of tumor necrosis factor (TNF)-related apoptosis-inducing ligands (TRAIL), which trigger an extrinsic apoptotic pathway via death receptors. Herein, we report TRAIL encapsulated in a bactericidal polypeptide-crosslinked nanogel that suppressed Klebsiella pneumoniae infection and overactive macrophages. Of interest, nanogel and TRAIL-nanogel treatments were more toxic towards LPS-activated cells than to naïve cells in cell viability assays. Treatment with TRAIL-nanogel significantly prolonged survival in septic mice and reduced bacterial numbers in circulation. As such, TRAIL-nanogel may be promising as a therapeutic agent for treating bacteria-infected diseases.