Poly-l-lysine/poly-l-glutamic acid-based layer-by-layer self-assembled multilayer film for nitric oxide gas delivery

Antimicrobial activity of gamma-poly (glutamic acid), a preservative coating for cherries

We investigated the minimum inhibitory concentration (MIC), antibacterial activity, and preservation ability of four molar masses of γ-polyglutamic acid (PGA) against Escherichia coli, Bacillus subtilis, and yeast. The antibacterial mechanism was determined based on the cell structure, membrane permeability, and microscopic morphology of the microorganisms. We then measured the weight loss, decay rate, total acid, catalase activity, peroxidase activity, and malondialdehyde content toward the possible use of PGA as a preservative coating for cherries. When the molar mass was greater than 700 kDa, the MIC for Escherichia coli and Bacillus subtilis was less than 2.5 mg/mL. The mechanism of action of the four molar masses of PGA was different with respect to the three microbial species, but a higher molar mass of PGA corresponded to stronger inhibition against the microbes. PGA of 2000 kDa molar mass damaged the microbial cellular structure, resulting in excretion of alkaline phosphatase, but PGA of 1.5 kDa molar mass affected the membrane permeability and the amount of soluble sugar. Scanning electron microscopy indicated the inhibitory effect of PGA. The antibacterial mechanism of PGA was related to the molar mass of PGA and the microbial membrane structure. Compared with the control, a PGA coating effectively inhibit the spoilage rate, delay the ripening, and prolong the shelf life of cherries.

Live Cells versus Fixated Cells: Kinetic Measurements of Biomolecular Interactions with the LigandTracer Method and Surface Plasmon Resonance Microscopy

Cell-based kinetic studies of ligand or candidate drug binding to membrane proteins have produced affinity and kinetic values that are different from measurements using purified proteins. However, ligand binding to fixated cells whose membrane constituents (e.g., proteins and their glycosylated forms) are partially connected by a cross-linking reagent has not been compared to that to live cells. Under the same experimental conditions for the LigandTracer method, we measured the interactions of fluorophore-labeled lectins and antibody molecules with glycans at HFF cells and the human epithelial growth receptor 2 at SKBR3 cells, respectively. In conjunction with surface plasmon resonance microscopy, the effects of labels and cell/sub-cell heterogeneity on binding kinetics were investigated. Our results revealed that, for cell constituents whose structures and functions are not closely dependent on cell viability, the ligand binding kinetics at fixated cells is only slightly different from that at live cells. The altered kinetics is explained on the basis of a less mobile receptor confined in a local environment created by partially interconnected protein molecules. We show that cell/sub-cell heterogeneity and labels on the ligands can alter the binding reaction more significantly. Thus, fixating cells not only simplifies experimental procedures for drug screening and renders assays more robust but also provides reliable kinetic information about drug binding to cell constituents whose structures are not changed by chemical fixation.

Opportunities for Nitric Oxide in Potentiating Cancer Immunotherapy

Despite nearly 30 years of development and recent highlights of nitric oxide (NO) donors and NO delivery systems in anticancer therapy, the limited understanding of exogenous NO's effects on the immune system has prevented their advancement into clinical use. In particular, the effects of exogenously delivered NO differing from that of endogenous NO has obscured how the potential and functions of NO in anticancer therapy may be estimated and exploited despite the accumulating evidence of NO's cancer therapy-potentiating effects on the immune system. After introducing their fundamentals and characteristics, this review discusses the current mechanistic understanding of NO donors and delivery systems in modulating the immunogenicity of cancer cells as well as the differentiation and functions of innate and adaptive immune cells. Lastly, the potential for the complex modulatory effects of NO with the immune system to be leveraged for therapeutic applications is discussed in the context of recent advancements in the implementation of NO delivery systems for anticancer immunotherapy applications. SIGNIFICANCE STATEMENT: Despite a 30-year history and recent highlights of nitric oxide (NO) donors and delivery systems as anticancer therapeutics, their clinical translation has been limited. Increasing evidence of the complex interactions between NO and the immune system has revealed both the potential and hurdles in their clinical translation. This review summarizes the effects of exogenous NO on cancer and immune cells in vitro and elaborates these effects in the context of recent reports exploiting NO delivery systems in vivo in cancer therapy applications.

Recent Advances in Poly(α-L-glutamic acid)-Based Nanomaterials for Drug Delivery

Poly(α-L-glutamic acid) (PGA) is a class of synthetic polypeptides composed of the monomeric unit α-L-glutamic acid. Owing to their biocompatibility, biodegradability, and non-immunogenicity, PGA-based nanomaterials have been elaborately designed for drug delivery systems. Relevant studies including the latest research results on PGA-based nanomaterials for drug delivery have been discussed in this work. The following related topics are summarized as: (1) a brief description of the synthetic strategies of PGAs; (2) an elaborated presentation of the evolving applications of PGA in the areas of drug delivery, including the rational design, precise fabrication, and biological evaluation; (3) a profound discussion on the further development of PGA-based nanomaterials in drug delivery. In summary, the unique structures and superior properties enables PGA-based nanomaterials to represent as an enormous potential in biomaterials-related drug delivery areas.

Crosslinked Polypeptide Films via RAFT-Mediated Continuous Assembly of Polymers

Polypeptide coatings are a cornerstone in the field of surface modification due to their widespread biological potential. As their properties are dictated by their structural features, subsequent control thereof using unique fabrication strategies is important. Herein, we report a facile method of precisely creating densely crosslinked polypeptide films with unusually high random coil content through continuous assembly polymerization via reversible addition-fragmentation chain transfer (CAP-RAFT). CAP-RAFT was fundamentally investigated using methacrylated poly-l-lysine (PLLMA) and methacrylated poly-l-glutamic acid (PLGMA). Careful technique refinement resulted in films up to 36.1±1.1 nm thick which could be increased to 94.9±8.2 nm after using this strategy multiple times. PLLMA and PLGMA films were found to have 30-50 % random coil conformations. Degradation by enzymes present during wound healing reveals potential for applications in drug delivery and tissue engineering.

Programmed BMP-2 release from biphasic calcium phosphates for optimal bone regeneration

This study aimed to fabricate a multi-layered biphasic calcium phosphate (BCP) platform for programmed bone morphogenetic protein-2 (BMP-2) release, which means to block the initial burst release and promote releasing during the differentiation phase of osteogenic cells. And it is to confirm in vivo whether this platform has osteogenic inductivity even when extremely low doses of BMP-2 are loaded compared to the conventional soaking method. Our strategy consisted of preparing a multilayer coating on BCP to minimize the contact between BMP-2 and BCP and allow the loading of BMP-2. The multilayer, which is surface-modified on BCP, is composed of an organosilicate and a natural polymer-based layer-by-layer (LbL) film. We applied (3-Aminopropyl)triethoxysilane (APTES) as an organosilicate was used for amine-functionalized BCP and (collagen/heparin)₅ film was used to delay and sustain BMP-2 release. The coated multilayer not only reduced the initial burst release by more than 50% but also loaded more BMP-2. For in vivo experiment, histomorphometric analysis, it was observed that the BCP platform loaded with extremely low concentration BMP-2 (0.01 mg/ml) induced a significantly larger amount of new bones at 8 weeks compared to the conventional soaking method in the rabbit calvarium onlay graft model.

Acceleration of Nitric Oxide Release in Multilayer Nanofilms through Cu(II) Ion Intercalation for Antibacterial Applications

Implant-derived bacterial infection is a prevalent cause of diseases, and no antibacterial coating currently exists that is biocompatible and that does not induce multidrug resistance. To this end, nitric oxide (NO) has been emerging as an effective antimicrobial agent that acts on a broad range of bacteria and elicits no known resistance. Here, a method for accelerating NO release from multilayered nanofilms has been developed for facilitating antibacterial activity. A previously reported multilayered nanofilm (nbi film) was fabricated by alternative deposition of branched polyethyleneimine (BPEI) and alginate via the layer-by-layer assembly method. N-Diazeniumdiolate, a chemical NO donor, was synthesized at the secondary amine moiety of BPEI within the film (nbi/NO film). Cu(II) ions can be incorporated into the film by forming chelating compounds with unreacted amines that have not been converted to NO donors. The increase of the amine protonation state in the chelate caused destabilization of the NO donor by reducing hydrogen bonding between the deprotonated amine and the NO donor. Thus, the Cu(II) ion-embedding film presented accelerated NO release and was further subjected to antibacterial testing to demonstrate the correlation between the NO release rate and the antibacterial activity. This study aimed to establish a novel paradigm for NO-releasing material design based on multilayered nanofilms by presenting the correlation between the NO release rate and the antibacterial effect.

Reference method for off-line analysis of nitrogen oxides in cell culture media by an ozone-based chemiluminescence detector

Nitric oxide (NO) and its by-products are important biological signals in human physiology and pathology particularly in the vascular and immune systems. Thus, in situ determination of the NO-related molecule (NO_x) levels using embedded sensors is of high importance particularly in the context of cellular biocompatibility testing. However, NO_x analytical reference method dedicated to the evaluation of biomaterial biocompatibility testing is lacking. Herein, we demonstrate a PAPA-NONOate-based reference method for the calibration of NO_x sensors. After, the validation of this reference method and its potentialities were demonstrated for the detection of the oxidative stress-related NO secretion of vascular endothelial cells in a 3D tissue issued from 3D printing. Such NO_x detection method can be an integral part of cell response to biomaterials. Graphical abstract.

Mg-Zn-Ca Alloys for Hemostasis Clips for Vessel Ligation: In Vitro and In Vivo Studies of Their Degradation and Response

To control the degradation rate of magnesium (Mg) alloys, chitosan (CHI) and L-glutamic acid (LGA) were used as coatings on Mg-Zn-Ca alloys via dip coating. In this study, either two or seven CHI/LGA layers were applied as a coating on Mg-2.8Zn-0.8Ca alloy (ZX31) and Mg-2.8Zn-0.8Ca hemostasis clips (ZX31 clips). The morphologies, compositions, and surface roughness of the specimens were characterized via scanning electron microscopy, Fourier transform infrared spectroscopy, and surface measurement devices. The degradation rates and behavior of the specimens were evaluated by immersing them in simulated body fluids and by applying these ZX31 clips on rabbits’ uterine tubes for five weeks. The specimen with seven layers (ZX31(CHI/LGA)₇) exhibited improved corrosion behavior when compared with ZX31 or ZX31(CHI/LGA)₂, with a reduced degradation rate of the Mg alloy in a simulated body environment. In vivo experiments showed that ZX31 clips exhibited good biocompatibilities in each group but could not maintain the clamping function for five weeks. The weight loss of ZX31(CHI/LGA)₇ was significantly lower than that of the other groups. Consequently, it was verified that CHI can be used as a protective layer on a magnesium alloy surface via in vitro and in vivo experiments.