Fabrication and characterization of transparent nanocomposite films based on poly (lactic acid)/polyethylene glycol reinforced with nano glass flake

Developing new biodegradable packaging with superior properties and advanced functionalities is one of the most emerging research areas of interest in food packaging. In this study, PLA/PEG-based nanocomposite films incorporated with different amounts of nano glass flake (NGF) (0, 0.5, 1, and 2 phr) were fabricated via casting solution for applications in food packaging. The ATR-FTIR displayed no chemical interaction between the PLA/PEG-based matrix and NGF particles. The scanning electron microscopy (SEM) observations exhibited a relatively smooth and homogeneous surface without defects. Incorporation of the NGF into the PLA/PEG-based matrix did not affect the color and opacity of the fabricated films. The prepared nanocomposite films were highly transparent and exhibited superior properties such as increased hydrophobicity, appreciable oxygen barrier properties, and enhanced thermal stability. Dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC) analysis confirmed the existence of a single glass-transition temperature (Tg) as evidence of miscibility. According to the research results, the PLA/PEG/NGF1 nanocomposite film significantly offered the best overall performance. This work has developed new insight into the potential application of nano glass flakes in food packaging.

Polysaccharide-based (kappa carrageenan/carboxymethyl chitosan) nanofibrous membrane loaded with antifibrinolytic drug for rapid hemostasis- in vitro and in vivo evaluation

This work aimed to establish a novel membrane consisting of hemostatic polysaccharides, kappa-carrageenan (KC), and carboxymethyl chitosan (CMC) in tandem with polyvinyl alcohol that spun together as a matrix and loaded with tranexamic acid (TXA) as antifibrinolytic agent for further coagulation effect during and after oral surgeries. The electrospinning of KC was done for the first time and in comparison of CMC has better hemostatic efficacy. The effect of the hemostat was investigated by its surface morphology (SEM), FTIR/ATR analysis, swelling behavior in both PBS and blood, hydrophilicity, porosity, mechanical properties, and cumulative release rate. The effect of materials and the drug concentration ratio were considered. The effect of acetic acid percent in aqueous solutions of CMC/PVA and KC/PVA on morphology was investigated. The cell culture assay showed that all membranes interacted well (98 %) with fibroblast cells attached and grown on the fabricated substrate. Furthermore, the membranes are evaluated by clotting time, whole blood clotting, hemocompatibility, and platelet and RBC adhesion tests. Also, the hemostatic performance of the membrane was analyzed in vivo, using the tail and liver bleeding model in rats. Therefore, TXA loading into CMC and KC dressing could be an attractive hemostatic system for various clinical applications.

Transdermal drug delivery system of lidocaine hydrochloride based on dissolving gelatin/sodium carboxymethylcellulose microneedles

In this study, it was aimed to introduce a transdermal drug delivery system with dissolving microneedles (DMNs) based on gelatin (GEL) and sodium carboxymethyl cellulose (NaCMC) for lidocaine hydrochloride (LidoHCl) delivery. Different ratios of GEL and NaCMC were mixed, loaded with an active agent of LidoHCl, and treated with glutaraldehyde (GTA) as a crosslinker agent. Prepared hydrogels were cast into a silicon mold. Hereby, microneedles (MNs) with 500 µm height, 35° needle angle, 40-µm tip radius, and 960-µm tip-to-tip distance were fabricated. Samples containing LidoHCl 40%, GEL/NaCMC 5:1 (wt/wt), and polymer/GTA ratio 3.1 (wt/wt) showed the highest drug release ability (t < 10 min) with proper mechanical properties in comparison with other samples. Due to the drug release in a short time (fewer than 10 min), this drug delivery system can be used for rapid local anesthesia for pain relief as well as before minor skin surgeries.

Graphical Abstract

Polysaccharide-based polyampholyte complex formation: Investigating the role of intra-chain interactions

The difference in inter-chain and intra-chain electrostatic attraction was investigated in polyelectrolyte and polyampholyte electrostatic complex formation. Three polymers with similar backbone molecular structures including chitosan (Ch) polycation, carboxymethyl cellulose (CMCe) polyanion, and carboxymethyl chitosan (CMCh) polyampholyte were used for this purpose. The turbidimetric, water content, and rheological measurements for polyampholyte self-complex showed more dependence on the ionic strength rather than the polyelectrolyte one. The degree of dissociation (α), dissociation constant (pKa), and intrinsic persistence length were calculated by applying the Katchalsky-Lifson model to potentiometric data. We studied the gyration radii as a function of Debye length and observed the polyampholyte chain contractions due to the intra-chain electrostatic attractions, which minimize the entropic gain of the inter-chain complex formation. This is in accordance with the decrease in pKa by α_c for CMCh which is the opposite of that for the Ch and CMCe samples. We also found that the polyampholyte has less intrinsic and electrostatic persistence length compared with both polyanion and polycation with similar chain structures indicating the impact of the inter-chain electrostatic interaction on the complex properties. This study deepens our insight about the behavior of CMCh and the nature of difference between CMCh and Ch/CMCe electrostatic complexes.

Albumin-loaded thermo/pH dual-responsive nanogels based on sodium alginate and poly (N-vinyl caprolactam)

During the past decades, many researchers have tried to encapsulate medicines in biopolymer nanogels as injectable medicines. In the present study, dual-responsive bovine serum albumin (BSA)-loaded nanogels prepared from sodium alginate grafted poly (N-vinyl caprolactam) (PNVCL) have been reported. First, PNVCL-g-sodium alginate (PNVCL-g-Alg) was synthesized through free radical polymerization, and then nanogels were obtained from ionic crosslinking of sodium alginate in the presence of BSA. FTIR spectra showed that PNVCL-g-Alg nanogels were successfully prepared. Turbidimetry and rheometry analyses demonstrated the cloud point temperature near the human body. Particle size was evaluated using FE-SEM and dynamic light scattering and it was found that the size of particles in dry and swollen state are about 30 and 280 nm, respectively. The effect of temperature and pH on BSA release was evaluated. By comparing the drug release behavior, we found that the release of the protein at the temperature above the cloud point is faster than that at the temperature below the cloud point. The pH sensitivity of BSA-loaded PNVCL-g-Alg was evaluated at pH 5.5 and 7.4 and showed that the drug release was faster at acidic pH than at neutral pH.

Magnetic dual-responsive semi-IPN nanogels based on chitosan/PNVCL and study on BSA release behavior

Magnetic thermoresponsive nanogels present a promising new approach for targeted drug delivery. In the present study, bovine serum albumin (BSA) loaded thermo-responsive magnetic semi-IPN nanogels (MTRSI-NGs) were developed. At first poly(N-vinyl caprolactam) (PNVCL) was synthesized by free radical polymerization and then MTRSI-NGs were prepared by crosslinking chitosan in presence of chitosan and Fe₃O₄. The formation of MTRSI-NGs has been confirmed by FTIR, and the average molecular weight of PNVCL was determined by GPC analysis. Rheological and turbidimetry analysis were used to determine lower critical solution temperature (LCST) of PNVCL and magnetic thermo-responsive nanogels (MTRSI-NGs) around 32 and 37 °C, respectively. FE-SEM analysis showed particle size at less than 20 nm in the dried state. Dynamic light scattering determined particle size at about 30 nm in a swelling state. The analysis of release behavior showed that the BSA release ratio at 40 °C was faster than 25 °C. The pH release behavior was evaluated at pH 5.5 and 7.4 and showed that the drug release rate at pH 5.5 was more rapid than pH 7.4. The results show MTRSI-NGs are applicable to protein targeted delivery by thermosensitive targeted drug delivery systems.

Controlled curcumin release from nanofibers based on amphiphilic-block segmented polyurethanes

A series of biodegradable amphiphilic-block segmented polyurethanes (SPUs) are designed and synthesized based on di-block and tri-block macrodiols of polycaprolactone (PCL) and polyethylene glycol (PEG). Curcumin, as a model herbal antibacterial agent, is used due to its effective inhibitory action against Gram-positive and Gram-negative bacteria. Curcumin-loaded nanofibers, with 400-900 nm diameter range, have been prepared by electrospinning of SPUs. The synthesized SPUs can be used for wound dressing applications due to their excellent mechanical properties and higher hydrophilicity in comparison to PCL-based polyurethane. The elongation-at-break of tri-block SPU with PEG-PCL-PEG soft segments is 350% when produced as an electrospun mat and that for film is 1500%. In vitro release of curcumin, examined by UV-Vis spectroscopy, shows a steady release during 18 days. The inclusion of PEG chains in the soft segment increases the hydrophilicity and biodegradation rate of the electrospun mats compared to a PCL-based polyurethane, which eventually results in a higher curcumin release rate. The antibacterial activity of 50 mg of 10% curcumin-loaded SPU nanofibers is about 100% and 93% against Escherichia coli (E. coli ATCC: 25922) and Staphylococcus aureus (S. aureus ATCC: 6538), respectively. Nontoxic behavior of the scaffolds is evaluated through MTT assay against L929 mouse fibroblast cells. The results show that the synthesized SPUs can be used as a nanoscale sustained release carrier. The SPU with PEG-PCL-PEG soft segments is an excellent candidate for wound dressing in tissues undergoing large deformations during normal activities.

Novel polyimides based on diamine containing thiazole units with thioether linkage and pyridine as pendent group

Three new organic-soluble polyimides (PIs) bearing flexible thioether linkages, thiazole, and pyridine ring units were synthesized from a novel thioether-bridged diamine monomer and commercially available aromatic dianhydrides (1–3) via chemical imidization method. The resulting polymers were obtained in high yields and possessed inherent viscosities in the range of 0.67–0.89. The PIs are characterized by Fourier-transform infrared (FTIR), nuclear magnetic resonance (NMR), differential scanning calorimetry, and thermogravimetric analysis (TGA). All of the PIs exhibited excellent solubility in polar solvent. The polymers showed good thermal stability with glass transition temperatures ( Tgs) in the range of 194–244°C, and decomposition temperatures ( T5%) exceeding 300°C were observed using TGA in nitrogen atmosphere for the current polymers.

[PhSiO1.5]8,10,12 as nanoreactors for non-enzymatic introduction of ortho, meta or para-hydroxyl groups to aromatic molecules

Traditional electrophilic bromination follows long established "rules": electron-withdrawing substituents cause bromination selective for meta positions, whereas electron-donating substituents favor ortho and para bromination. In contrast, in the [PhSiO_1.5]_8,10,12 silsesquioxanes, the cages act as bulky, electron withdrawing groups equivalent to CF₃; yet bromination under mild conditions, without a catalyst, greatly favors ortho substitution. Surprisingly, ICl iodination without a catalyst favors (>90%) para substitution [p-IC₆H₄SiO_1.5]_8,10,12. Finally, nitration and Friedel-Crafts acylation and sulfonylation are highly meta selective, >80%. In principle, the two halogenation formats coupled with the traditional electrophilic reactions provide selective functionalization at each position on the aromatic ring. Furthermore, halogenation serves as a starting point for the synthesis of two structural isomers of practical utility, i.e. in drug prospecting. The o-bromo and p-iodo compounds are easily modified by catalytic cross-coupling to append diverse functional groups. Thereafter, F^-/H₂O₂ treatment cleaves the Si-C bonds replacing Si with OH. This represents a rare opportunity to introduce hydroxyl groups to aromatic rings, a process not easily accomplished using traditional organic synthesis methods. The as-produced phenol provides additional opportunities for modification. Each cage can be considered a nanoreactor generating 8-12 product molecules. Examples given include syntheses of 4,2'-R,OH-stilbenes and 4,4'-R,OH-stilbenes (R = Me, CN). Unoptimized cleavage of the Br/I derivatives yields 55-85% phenol. Unoptimized cleavage of the stilbene derivatives yields 35-40% (3-5 equivalents of phenol) in the preliminary studies presented here. In contrast, meta R-phenol yields are 80% (7-10 mol per cage).

Super RLuc8-sFv; a new luciferase-labeled probe for detection of human CD4+ cells

A probe has been designed, produced and assayed for the detection of T-helper cells. The sFv fragment fused to the C-terminus of super Renilla luciferase 8 (Super RLuc8) and the probe successfully used for detection of human CD4+ cells using luminometer.

CD4 D3-binding probe: a novel fluorescence tool for detection and enumeration of CD4+ cells

A new and advanced CD4-binding reporter has been designed, produced and functionally assayed for the detection of T-helper cells.

Dynamic mechanical and thermal behavior evaluation of an epoxy/anhydride/nano-aluminum oxide composite system

The conventional properties of composites may be improved by incorporating the nanoparticles in polymer matrix to achieve high-performance polymer nanocomposites. In this respect, a commercial formulation of an epoxy electrical insulator was prepared by the chemical reaction of bisphenol A-based epoxy resin with an anhydride hardener and mixed with microsilica as filler. The effect of different contents of nano-aluminum oxide on dynamic mechanical and thermal properties of the cast epoxy composite was evaluated. The obtained result revealed that the effect of uniform dispersion of nanoparticles on storage modulus was as important as the filler content. In other words, increasing nanoparticle contents up to 10 wt% could not necessarily improve the properties of the nanocomposite while a uniform dispersion of nanofiller of just 1 wt% in a sample provided an efficient nanocomposite in which the values of storage modulus, dissipation factor and thermal stability were optimized. Furthermore, the combination of stiffness and high damping may be achieved in well-dispersed nanocomposites where strong interfacial interaction dominates between particle surface and polymer chain segments. This kind of sample possesses the highest thermal stability as well.

Application of experimental design for extraction of BHA and BHT from edible vegetable oil and their determination using HPLC

The optimal conditions of liquid–liquid extraction of two synthetic phenolic antioxidants, BHA and BHT were investigated in five Iranian edible vegetable oil samples using the central composite design. Stepwise multiple linear regression method was used for construction of different models based on the experimental data. Optimum conditions for BHA and BHT were achieved using 3 ml of ethanolic solution containing (0.25% v/v) of glacial acetic acid, three extractions and a mixing time of 10 minutes. Analytes were separated using HPLC with a C 18 column using methanol:water:glacial acetic acid (75:24:1, v/v/v) as the mobile phase. The limit of detections, linear ranges and relative standard deviation ( n = 7 ) were 0.04 μg/g−1 , 0.5– 200 μg/g−1 and 2.6% for BHA and 0.30 μg/g−1 , 1.0– 200 μg/g−1 and 4.20% for BHT, ( r 2 > 0 . 9 9 ), respectively. Amounts of BHA and BHT in analyzed oil samples were in the ranges of 29.8– 54.5 μg/g−1 and 0.0– 6.8 μg/g−1 respectively.