Stability-indicating HPLC assay for lysine-proline-valine (KPV) in aqueous solutions and skin homogenates.

A simple, sensitive and stability-indicating high-performance liquid chromatographic (HPLC) assay method was developed and validated for a bioactive peptide, lysine-proline-valine (KPV) in aqueous solutions and skin homogenates. Chromatographic separation was achieved on a reversed phase Phenomenex C18 column (4.6 × 250 mm, packed with 5 µm silica particles) with a gradient mobile phase consisting of 0.1% trifluoroacetic acid (TFA) in water (A) and 0.1% TFA in acetonitrile (B). The proposed HPLC method was validated with respect to accuracy, precision, linearity, repeatability, limit of detection (LOD) and limit of quantitation (LOQ). The calibration curve was linear with a correlation coefficient (r) of 0.9999. Relative standard deviation values of accuracy and precision experiments were <2. The LOD and LOQ of KPV were 0.01 and 0.25 µg/mL, respectively. Under stress conditions (acid, alkali and hydrogen peroxide) KPV yielded lys-pro-diketopiperazine as major degradation product, which was identified by flow injection MS analysis. The developed HPLC method was found to be efficient in separating the active peptide from its degradation products generated under various stress conditions. Also, the validated method was able to separate KPV from other peaks arising from endogenous components of the skin homogenate.

Effect of Low-Temperature Plasma Treatment on Starch-Based Biochar and Its Reinforcement for Three-Dimensional Printed Polypropylene Biocomposites.

Uniform dispersion and high interfacial adhesion are two of the most difficult components of creating an ideally reinforced polymer composite. One of the solutions could be surface engineering of reinforcing filler materials utilizing innovative technologies. Low-temperature plasma treatments in the presence of sulfur hexafluoride (SF6) gas are proposed as a sustainable alternative to modify the surface properties of biochar carbon synthesized from sustainable starch-based packaging waste via a high-temperature/pressure pyrolysis reaction in the current study. X-ray photoelectron spectroscopy tests revealed that plasma treatments were effective in the fluorination of biochar carbon like wet chemical methods. By delivering fluorine-related functionalities only on the surface of the carbon, plasma treatments were efficient in changing the surface properties of biochar carbon while keeping the carbon's beneficial bulk properties intact, which is unique to this method. The modified biochar was effectively utilized to reinforce polypropylene. Mechanical properties like tensile strength improved by 91% when compared to neat polymers and 31% when compared to untreated biochar-reinforced polymers at 0.75 wt % loadings. Elongation at break increased from 12.7 to 38.78, showing an impressive 216% increase due to effective reinforcement by plasma functionalization. The decomposition onset temperature and maximum rate of decomposition temperature increased by 60 and 49 °C, respectively, when compared to neat polymers. Plasma-modified biochar-reinforced three-dimensional printed samples have shown promise to be utilized for the development of composite parts using additive manufacturing methods.

Influence of Fish Scale-Based Hydroxyapatite on Forcespun Polycaprolactone Fiber Scaffolds.

Marine waste byproducts, especially fish scales, have proved to be one of the most prominent sources for developing sustainable materials for various applications including biomedical applications. Hydroxyapatite (HAp), being one of such biomaterials that can be synthesized from the massive fish-based waste, has received plentitude of attention due to its excellent ability to promote cell growth and proliferation. However, understanding the influence of HAp on polymer matrices that are tailored for biomedical applications is still a challenge. This study is intended to develop a sophisticated yet inexpensive method to obtain nonwoven polycaprolactone (PCL) nanofibrous scaffolds and analyze the influence of calcium-deficient nanoporous hydroxyapatite (n-HAp) on the thermal, mechanical, and biological properties of these scaffolds. The n-HAp is synthesized using two different types of fish scales, carpa (CA) and pink perch (PP), by calcination followed by nanomilling. The synthesized n-HAp powder is characterized by using X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy. The PCL fibrous scaffolds were developed using a novel forcespinning technique with n-HAp as the filler. The morphology of the scaffolds was characterized using SEM and Raman spectroscopy. SEM and TEM results have confirmed the size reduction of the HAp powder after nanomilling. Thermal properties were analyzed using thermogravimetric analysis and differential scanning calorimetry. The major degradation temperature has increased by 3° and was observed to be 398° for 1 wt % filler loading for both carpa and pink perch-derived n-HAp. The increase in filler content has increased the residue left after decomposition and is 4% for 5 wt % filler loading. The crystallinity percent has increased by 7% compared to neat fibers for 1 wt % filler loading. Mechanical properties were tested using tensile tests. The tensile test strength has shown 32% improvement for 1 wt % compared to neat fibers. Cell viability tests were performed using hFOB cells which have shown significant cell growth for a high filler loading of 5 wt %. The results suggest that both CA-n-HAP and PP-n-Hap-incorporated fibrous scaffolds can be used potentially for biomedical applications after careful investigation of the scaffold behavior with longer incubation periods.

Synthesis of Ag/CNT hybrid nanoparticles and fabrication of their nylon-6 polymer nanocomposite fibers for antimicrobial applications.

Ag-coated CNTs hybrid nanoparticles (Ag/CNTs) were prepared by ultrasonic irradiation of dimethylformamide (DMF) and silver (I) acetate precursors in the presence of CNTs. The morphology of Ag/CNTs was characterized using x-ray diffraction and transmission electron microscopy (TEM) techniques. The Nylon-6 powder and 1 wt% Ag/CNTs mixture was dispersed uniformly using a noncontact spinning technique. The dried mixture was melted in a single screw extrusion machine and then extruded through an orifice. Extruded filaments were later stretched and stabilized by sequentially passing them through a set of tension adjusters and a secondary heater. The Nylon-6/Ag/CNT hybrid polymer nanocomposite (HPNC) fibers, which were of approximately 80 microm size, were tested for their tensile properties. The failure stress and modulus of the extruded HPNC fibers (doped with 1% Ag/CNTs) was about 72.19 % and 342.62% higher than the neat extruded Nylon-6 fiber, respectively. DSC results indicated an increase in the thermal stability and crystallization for HPNC fibers. The antibacterial activity of the Ag-coated CNTs, commercial Ag, neat Nylon-6 and plain CNTs were evaluated. Ag-coated CNTs at 25 microg demonstrated good antimicrobial activity against four common bacterial pathogens as tested by the Kirby-Bauer assay. The mean diameters of the zones of inhibition were 27.9 +/- 6.72 mm, 19.4 +/- 3.64 mm, 21.9 +/- 4.33 mm, and 24.1 +/- 4.14 mm, respectively, for Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli and Salmonella enterica serovar Typhimurium. By comparison, those obtained using the broad spectrum antibiotic amoxicillin-clavulanic acid were 37.7 +/- 2.13 mm, 28.6 +/- 4.27 mm, 22.6 +/- 1.27 mm, and 27.0 +/- 1.41 mm, respectively, for the same strains. The zones of inhibition obtained for Nylon-6 Ag-coated CNT powder at 25 microg were also high, ranging from 15.2 to 25.3 mm in contrast to commercial silver or neat Nylon-6, which did not inhibit the bacterial strains tested. Further, the Nylon-6 nanocomposite fibers infused with Ag/CNTs inhibited bacterial growth by 11-20%. Our results suggest that nylon nanocomposite fibers infused with Ag-coated CNTs have significant antimicrobial activity.

Eggshell Based Nano-Engineered Hydroxyapatite and Poly(lactic) Acid Electrospun Fibers as Potential Tissue Scaffold.

Nanocomposite electrospun fibers were fabricated from poly(lactic) acid (PLA) and needle-like hydroxyapatite nanoparticles made from eggshells. The X-ray diffraction spectrum and the scanning electron micrograph showed that the hydroxyapatite particles are highly crystalline and are needle-liked in shape with diameters between 10 and 20 nm and lengths ranging from 100 to 200 nm. The microstructural, thermal, and mechanical properties of the electrospun fibers were characterized using scanning electron microscope (SEM), thermogravimetric analysis (TGA), dynamic scanning calorimetry (DSC), and tensile testing techniques. The SEM study showed that both pristine and PLA/EnHA fibers surfaces exhibited numerous pores and rough edges suitable for cell attachment. The presence of the rod-liked EnHA particles was found to increase thermal and mechanical properties of PLA fibers relative to pristine PLA fibers. The confocal optical images showed that osteoblast cells were found to attach on dense pristine PLA and PLA/HA-10 wt% fibers after 48 hours of incubation. The stained confocal optical images indicated the secretion of cytoplasmic extension linking adjoining nuclei after 96 hours of incubation. These findings showed that eggshell based nanohydroxyapatite and poly(lactic acid) fibers could be potential scaffold for tissue regeneration.

Transdermal Iontophoretic Delivery of Lysine-Proline-Valine (KPV) Peptide Across Microporated Human Skin.

Lysine-proline-valine (KPV) is a C-terminal peptide fragment of α-melanocyte stimulating hormone with potent anti-inflammatory properties. Present study investigates various transdermal enhancement strategies such as iontophoresis (ITP), microneedles (MN), and their combination (ITP + MN) on KPV delivery across dermatomed human skin. KPV attains a positive charge at pH less than 7.0, thus anodal ITP was used. The influence of current strength, KPV concentration, and duration of current application on the KPV delivery was investigated. At defined ITP parameters, the influence of MN on KPV delivery (ITP + MN) across skin was also determined. KPV permeation was less than detectable levels (limit of detection, 0.01 µg/mL) by simple passive diffusion. However, KPV permeation was increased to 4.4 µg/cm2/h by MN treatment. Furthermore, ITP and ITP + MN increased the permeation rate by 8 and 35 fold, respectively, as compared to MN alone. The skin retention levels of KPV by MN, ITP, and ITP + MN were increased by 5, 10, and 10 fold, respectively, as compared to passive diffusion. Confocal studies indicate that fluorescein isothiocyanate-labeled KPV migrated through the stratum corneum, along the microchannels and into the lower epidermal tissue because the fluorescence was observed beyond the depth of 100 µm.

Nanoengineered Eggshell-Silver Tailored Copolyester Polymer Blend Film with Antimicrobial Properties.

In this study, the reinforcement effect of different proportions of eggshell/silver (ES-Ag) nanomaterial on the structural and antimicrobial properties of 70/30 poly(butylene-co-adipate terephthalate)/polylactic acid (PBAT/PLA) immiscible blends was investigated. The ES-Ag was synthesized using a single step ball milling process and characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). These results confirmed the existence of silver nanoparticles (Ag NPs) in the interstitial spaces of the eggshell particles. The thin films in this study were prepared using hot melt extrusion and 3D printing for mechanical and antimicrobial testing, respectively. These films were also characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), XRD, tensile testing, and antimicrobial analysis. It was found that the incorporation of ES-Ag (0.5-2.0% content) compromised the tensile properties of the blend, due to poor interaction between the matrix and the ES-Ag in the ternary systems, but thermal analysis revealed improvement in the onset of degradation temperature and char yield at 500 °C. Though film toughness was better than that of PLA, the strength was lower, yet synergistic to those of PBAT and PLA. In general, the PBAT/PLA/ES-Ag ternary system had properties intermediate to those of the pure polymers. In vitro assessment of the antimicrobial activity of these films conducted on Listeria monocytogenes and Salmonella Enteritidis bacteria revealed that the blend composite films possessed bacteriostatic effects, due to the immobilized ES-Ag nanomaterials in the blend matrix. Atomic absorption spectroscopy (AAS) analysis of water and food samples exposed to the films showed that Ag NPs were not released in distilled water and chicken breast after 72 and 168 h, respectively.

In Situ Strategy to Encapsulate Antibiotics in a Bioinspired CaCO3 Structure Enabling pH-Sensitive Drug Release Apt for Therapeutic and Imaging Applications.

Herein we demonstrate a bioinspired method involving macromolecular assembly of anionic polypeptide with cationic peptide-oligomer that allows for in situ encapsulation of antibiotics like tetracycline in CaCO3 microstructure. In a single step one-pot process, the encapsulation of the drug occurs under desirable environmentally benign conditions resulting in drug loaded CaCO3 microspheres. While this tetracycline-loaded sample exhibits pH dependent in vitro drug-release profile and excellent antibacterial activity, the encapsulated drug or the dye-conjugated peptide emits fluorescence suitable for optical imaging and detection, thereby making it a multitasking material. The efficacy of tetracycline loaded calcium carbonate microspheres as pH dependent drug delivery vehicles is further substantiated by performing cell viability experiments using normal and cancer cell lines (in vitro). Interestingly, the pH-dependent drug release enables selective cytotoxicity toward cancer cell lines as compared to the normal cells, thus having the potential for further development of therapeutic applications.

Sonochemical synthesis and rheological properties of shear thickening silica dispersions.

A sonochemical method has been developed to synthesize shear thickening fluid. This shear thickening fluid (STF) is composed of hard silicon dioxide nanoparticles and polyethylene glycol (PEG) liquid polymer. The combination of flow-able and hard components at a particular composition, results a material with remarkable rheological properties that is suitable for liquid body armor applications. In the present study nine types of STF's have been synthesized with two different types of silica nanoparticles (15 nm and 200 nm) and polyethylene glycol at various weight fractions using a high intensity ultrasonic irradiation. The resultant STF samples were tested for their rheological and thermal properties. The advantages and disadvantages of this process have been discussed.

Synthesis and characterization of diamond-coated CNTs and their reinforcement in Nylon-6 single fiber.

Diamond nanoparticle (DN)-coated CNTs were synthesized using a cationic surfactant-assisted sonochemical method. The as-prepared DN coated CNTs were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The results show that the DNs were coated on the outer wall surface of CNTs. The DN-coated CNTs were infused in Nylon-6 polymer through a melt extrusion process to form nanocomposite fibers that were tested for their tensile properties. The ultimate tensile strength is found to be 363 MPa for DN/CNTs/Nylon-6 single fibers as compared to 240 MPa for neat Nylon-6 single fibers. These results were also compared with Nylon-6 fibers infused with pristine CNTs and pristine DNs.

Alignment of carbon nanotubes and reinforcing effects in nylon-6 polymer composite fibers.

Alignment of pristine carbon nanotubes (P-CNTs) and fluorinated carbon nanotubes (F-CNTs) in nylon-6 polymer composite fibers (PCFs) has been achieved using a single-screw extrusion method. CNTs have been used as filler reinforcements to enhance the mechanical and thermal properties of nylon-6 composite fibers. The composites were fabricated by dry mixing nylon-6 polymer powder with the CNTs as the first step, then followed by the melt extrusion process of fiber materials in a single-screw extruder. The extruded fibers were stretched to their maxima and stabilized using a godet set-up. Finally, fibers were wound on a Wayne filament winder machine and tested for their tensile and thermal properties. The tests have shown a remarkable change in mechanical and thermal properties of nylon-6 polymer fibers with the addition of 0.5 wt% F-CNTs and 1.0 wt% of P-CNTs. To draw a comparison between the improvements achieved, the same process has been repeated with neat nylon-6 polymer. As a result, tensile strength has been increased by 230% for PCFs made with 0.5% F-CNTs and 1% P-CNTs as additives. These fibers have been further characterized by DSC, Raman spectroscopy and SEM which confirm the alignment of CNTs and interfacial bonding to nylon-6 polymer matrix.