Preparation and characterization of chitosan-polyvinyl alcohol blend hydrogels for the controlled release of nano-insulin

Chitosan (CS)-polyvinyl alcohol (PVA) blend hydrogels were prepared using glutaraldehyde as the cross-linking agent. The obtained hydrogels, which have the advantages of both PVA and CS, can be used as a material for the transdermal drug delivery (TDD) of insulin. The nano-insulin-loaded hydrogels were prepared under the following conditions: 1.2 g of polyethylene glycol, 1.5 g of CS, 1.2 g of PVA, 1.2 mL of 1% glutaraldehyde solution, 16 mL of water, and 40 mg of nano-insulin with 12 min of mixing time and 3 min of cross-linking time. The nano-insulin-loaded hydrogels were characterized using scanning electron microscopy, energy dispersive spectrometry, Fourier-transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction, and its mechanical properties were analyzed. The results show that all molecules in the hydrogel have good compatibility and they formed a honeycomb-like structure. The hydrogel also showed good mechanical and thermal properties. The in vitro drug release of the hydrogel showed that the nano-insulin accorded with Fick's first law of diffusion and it has a high permeation rate (4.421 μg/(cm² h)). These results suggest that the nano-insulin-loaded hydrogels are a promising non-invasive TDD system for diabetes chemotherapy.     

Determination of the structural changes by FT-IR, Raman, and CP/MAS C NMR spectroscopy on retrograded starch of maize tortillas

The nixtamalization, production and storage of tortillas in refrigeration cause several changes on the starch structure, resulting in an increased crystallinity and therefore a higher content of resistant starch. The IR analysis for resistant starch (RS) showed a band at 1047 cm⁻¹ associated to the retrogradation process; this band was due to the weakening of the intermolecular H-bonds. These associated together to form ordered regions. The Raman analysis shows a characteristic band at 856 cm⁻¹ corresponding to C-C skeletal modes of glucose of α-1,4 glycosidic linkage starches, and a band at 480 cm⁻¹ attributed to skeletal vibrations of the pyranose ring in the glucose unit of starches. These changes may be related to the polymerization degree of the starch molecules, as well as to the retrogradation of amylose and amylopectin. The spectrum of ¹³C CP-MAS/NMR for RS3 supports the results obtained by IR and Raman. Lipidic and proteic groups were observed which may be in the form of complexes with amylose. One can proclaim that the existence of the salt form is induced and stabilized by the interactions dominating the V amylose structure in the solid state.     

Synthesis and properties of carrageenan grafted copolymer with poly(vinyl alcohol)

The aim of this work was to prepare a carrageenan-g-poly(vinyl alcohol) (CG-g-PVA) polymer using potassium persulphate as an initiator. The effect of different ratios of the polymer blends on the parameters of the grafted polymer was investigated. The grafting ratio decreased with an increase of the CG content in the graft copolymer. The resulting CG-g-PVA was characterized by ATR-FTIR, tensile strength, elongation at break, swelling ratio, contact angle and biodegradation in soil. From the ATR-FTIR the 3,6-anhydride-galactose of the CG showed a peak at 927 cm⁻¹ that was absent in the CG-g-PVA and the ether linkage of PVA-g-CG between the hydroxyl group of PVA and the 3,6-anhydride-galactose of CG showed a peak at 1089 cm⁻¹ in the graft copolymer. The tensile strength and elongation at break decreased with an increase of the CG due to its phase separation. The highest tensile strength was observed at 2:8 CG/PVA. In addition, the swelling ratio decreased and the contact angle increased as a function of the increase of the CG in the grafted copolymer. The best ratio of CG-g-PVA was 2:8 CG/PVA. This graft copolymer was easily biodegraded in natural soil.     

Extraction and chemical characterization of starch from S. lycocarpum fruits

In this study the pulp from Solanum lycocarpum fruits was used as raw material for extraction of starch, resulting in a yield of 51%. The starch granules were heterogeneous in size, presenting a conical appearance, very similar to a high-amylose cassava starch. The elemental analysis (CHNS) revealed 64.33% carbon, 7.16% hydrogen and 0.80% nitrogen. FT-IR spectroscopy showed characteristic peaks of polysaccharides and NMR analysis confirmed the presence of the α-anomer of d-glucose. The S. lycocarpum starch was characterized by high value of intrinsic viscosity (3515 mPa s) and estimated molecular weight around 645.69 kDa. Furthermore, this starch was classified as a B-type and high amylose content starch, presenting 34.66% of amylose and 38% crystallinity. Endothermic transition temperatures (T_o = 61.25 °C, T_p = 64.5 °C, T_c = 67.5 °C), gelatinization temperature (ΔT = 6.3 °C) ranges and enthalpy changes (ΔH = 13.21 J g⁻¹) were accessed by DCS analysis. These results make the S. lycocarpum fruit a very promising source of starch for biotechnological applications.     

Carbon/silica composite fabricated from rice husk by means of binderless hot-pressing

A carbon/silica composite designed for use under compressive loads was fabricated from rice husk (RH), an agricultural waste material. RH was pulverized by using a planetary ball mill, then carbonized and molded into the precursor by means of hot-pressing without using any binders. A compression of 100 MPa was intermittently applied to the RH powder heated from room temperature to 150 °C, and then to 280 °C. The precursor, the bulk density of which was 1.37 g/cm³, was sintered for further densification at up to 1400 °C without compression, in nitrogen gas. The smaller particle size of the pulverized RH was beneficial for densifying the carbon/silica composite and increasing its compressive strength. Sintering at 800 °C for 1 h in nitrogen gas provided the maximum bulk density of 1.52 g/cm³ and the maximum Vickers hardness at the surface of 343 HV. The maximum compressive strength was measured to be 55.7 MPa using a sintering temperature of 1200 °C.     

Preparation and characterization of glycerol plasticized-pea starch/ZnO–carboxymethylcellulose sodium nanocomposites

Among natural polymers, starch is one of the most promising biodegradable materials because it is a renewable bioresource that is universally available and of low cost. However, the properties of starch-based materials are not satisfactory. One approach is the use of nano-filler as reinforcement for starch-based materials. In this paper, a nanocomposite is prepared using ZnO nanoparticles stabilized by carboxymethylcellulose sodium (CMC) as the filler in glycerol plasticized-pea starch (GPS) matrix by the casting process. According to the characterization of ZnO–CMC particles with Fourier transform infrared (FTIR), Ultraviolet–visible (UV–vis), X-ray diffraction (XRD), transmission electron microscope (TEM) and thermogravimetric analysis (TG), ZnO (about 60 wt%) is encapsulated with CMC (about 40 wt%) in ZnO–CMC particles with the size of about 30–40 nm. A low loading of ZnO–CMC particles can obviously improve the pasting viscosity, storage modulus, the glass transition temperature and UV absorbance of GPS/ZnO–CMC nanocomposites. When the ZnO–CMC contents vary from 0 to 5 wt%, the tensile yield strength increase from 3.94 MPa to 9.81 MPa, while the elongation at break reduce from 42.2% to 25.8%. The water vapor permeability decrease from 4.76 × 10⁻¹⁰ to 1.65 × 10⁻¹⁰ g m⁻¹ s⁻¹ Pa⁻¹.     

Effect of starch addition on the biological conversion and microbial community in a methanol-fed UASB reactor during long-term continuous operation

The effect of starch addition on the microbial composition and the biological conversion was investigated using two upflow anaerobic sludge bracket (UASB) reactors treating methanolic wastewater: one reactor was operated with starch addition, and another reactor was operated without starch addition. Approximately 300 days of operation were performed at 30 kg COD/m³/d, and then, the organic load of the reactors was gradually increased to 120 kg COD/m³/d. Successful operation was achieved at 30 kg COD/m³/d in both reactors; however, the methanol-fed reactor did not perform well at 120 kg COD/m³/d while the methanol-starch-fed reactor did. The granule analysis revealed the granule developed further only in the methanol-starch-fed reactor. The results of the microbial community analysis revealed more Methanosaeta cells were present in the methanol-starch-fed reactor, suggesting the degradation of starch produced acetate as an intermediate, which stimulated the growth of Methanosaeta cells responsible for the extension of granules.     

A comparative study of freezing single cells and spheroids: Towards a new model system for optimizing freezing protocols for cryobanking of human tumours

Cryopreservation of human tumour cells and tissue is a valuable tool for retrospective analysis and for the transport and handling of biopsy material. Tumour tissue consists of different cell types, which have different optimal freezing conditions, and extracellular matrix. A well-defined and authentic model system is required for developing new freezing protocols and media. This work describes the use of L929 and PC-3 spheroids as new model systems for freezing human tumours. Cell suspension and spheroids were frozen in different vessels (1 ml cryovials and a special, cryo-compatible 30 × 25 μl multi well plate) at slow rate (1 °C/min). Freezing media were combinations of culture or tumour transport medium (Liforlab^®) with the cryoprotective agents, Me₂SO, trehalose and modified starch. We also present a new method of evaluating the viability of three dimensional multicellular systems to compare thawed spheroids objectively. Best viability (70%) of L929 spheroids occurred with a combination of Liforlab^® and starch hydrolysis product. The best cryopreservation results for spheroids were found with extracellular cryoprotectants, while optimum viability of single cells was achieved with Me₂SO.     

Ozone gas affects physical and chemical properties of wheat (Triticum aestivum L.) starch

In this experiment, bread wheat flour and isolated wheat starch were treated with ozone gas (1,500 mg/kg at 2.5 L/min) for 45 min and 30 min, respectively. Starch was isolated from treated flour. Ozone treated starch and starch isolated from ozone treated flour had similar chemical and physical properties. Chemical analysis of starch isolates indicated depolymerization of high molecular weight amylopectins; with a subsequent increase in low molecular weight starch polymers as a result of starch hydrolysis. Ozone treatment resulted in elevated levels of carboxylic groups and decreased total carbohydrate content in amylopectin fractions. ¹H NMR results indicated formation of a keto group [(1→4)-3 keto] at the H-2 terminal (proton at C-2 position) and β-glucuronic acid at the H-1 terminal (proton at C-1 position). DSC transition temperatures and change in enthalpy were not affected by ozone treatment. Increased swelling power and RVA breakdown were observed in starch from ozone treated samples.     

Purification and characterization of a thiol amylase over produced by a non-cereal non-leguminous plant, Tinospora cordifolia

A 43 kDa α-amylase was purified from Tinospora cordifolia by glycogen precipitation, ammonium sulfate precipitation, gel filtration chromatography, and HPGPLC. The enzyme was optimally active in pH 6.0 at 60 °C and had specific activity of 546.2 U/mg of protein. Activity was stable in the pH range of 4-7 and at temperatures up to 60 °C. PCMB, iodoacetic acid, iodoacetamide, DTNB, and heavy metal ions Hg²⁺ > Ag⁺ > Cd²⁺ inhibited enzyme activity while Ca²⁺ improved both activity and thermostability. The enzyme was a thiol amylase (3 SH group/mole) and DTNB inhibition of activity was released by cysteine. N-terminal sequence of the enzyme had poor similarity (12-24%) with those of plant and microbial amylases. The enzyme was equally active on soluble starch and amylopectin and released maltose as the major end product.     

Effects of fabrication on the mechanics,microstructure and micromechanical environment of small intestinal submucosa scaffolds for vascular tissue engineering

In small intestinal submucosa scaffolds for functional tissue engineering, the impact of scaffold fabrication parameters on success rate may be related to the mechanotransductory properties of the final microstructural organization of collagen fibers. We hypothesized that two fabrication parameters, 1) preservation (P) or removal (R) of a dense collagen layer present in SIS and 2) SIS in a final dehydrated (D) or hydrated (H) state, have an effect on scaffold void area, microstructural anisotropy (fiber alignment) and mechanical anisotropy (global mechanical compliance). We further integrated our experimental measurements in a constitutive model to explore final effects on the micromechanical environment inside the scaffold volume. Our results indicated that PH scaffolds might exhibit recurrent and large force fluctuations between layers (up to 195 pN), while fluctuations in RH scaffolds might be larger (up to 256 pN) but not as recurrent. In contrast, both PD and RD groups were estimated to produce scarcer and smaller fluctuations (not larger than 50 pN). We concluded that the hydration parameter strongly affects the micromechanics of SIS and that an adequate choice of fabrication parameters, assisted by the herein developed method, might leverage the use of SIS for functional tissue engineering applications, where forces at the cellular level are of concern in the guidance of new tissue formation.     

Multinuclear NMR and molecular modelling investigations on the structure and equilibria of complexes that form in aqueous solutions of Ca and gluconate

Complexation of d-gluconate (Gluc⁻) with Ca²⁺ has been investigated via ¹H, ¹³C and ⁴³Ca NMR spectroscopy in aqueous solutions in the presence of high concentration background electrolytes (1 M ? I ? 4 M (NaCl) ionic strength). From the ionic strength dependence of its formation constant, the stability constant at 6 ? pH ? 11 and at I → 0 M has been derived (). The protonation constant of Gluc⁻ at I = 1 M (NaCl) ionic strength was also determined and was found to be log K_a = 3.24 ± 0.01 (¹³C NMR) and log K_a = 3.23 ± 0.01 (¹H NMR). It was found that ¹H and ¹³C NMR chemical shifts upon complexation (both with H⁺ and with Ca²⁺) do not vary in an unchanging way with the distance from the Ca²⁺/H⁺ binding site. From 2D ¹H-⁴³Ca NMR spectra, simultaneous binding of Ca²⁺ to the alcoholic OH on C2 and C3 was deduced. Molecular modelling results modulated this picture by revealing structures in which the Gluc⁻ behaves as a multidentate ligand. The five-membered chelated initial structure was found to be thermodynamically more stable than that derived from a six-membered chelated initial structure.     

Hormone-sensitive lipase is critical mediators of acute exercise-induced regulation of lipolysis in rat adipocytes

The purpose of the present study was to investigate the effect of acute exercise on lipolysis via coordination of hormone-sensitive lipase (HSL) and scaffold proteins, i.e., perilipin A and comparative gene identification-58 (CGI-58), in rat primary adipocytes. Glycerol release was significantly elevated immediately (0 h) and three hours (3 h) after exercise. Both activity and localization to the pellet of HSL were significantly greater in the pellet fraction, which is included in lipid droplet associated-proteins, than in the supernatant fraction. In the pellet fraction, although neither perilipin A nor CGI-58 protein level changed, level of perilipin A/CGI-58 complex was significantly reduced, accompanied by up-regulated association of perilipin A/HSL at 0 h and 3 h after exercise. On the other hand, there were no changes in these molecules at 24 h after exercise, despite a significant decrease in lipolysis that was observed in response to isoproterenol. These findings suggest that acute exercise enhances lipolysis up to at least 3 h after exercise in a manner dependent on modification of HSL and its association with and alteration in scaffold protein.     

Freeze-thaw stability of starches from different botanical sources: Correlation with structural features

Native starches from twenty-six botanical sources were determined for their structural features and stability against freeze-thaw treatments. Starch gels (5%, w/w) were prepared and repeatedly freeze-thawed up to five cycles by storing at −18 °C for 21 h and then at 30 °C for 3 h. Water release (syneresis) from the thawed gel after the 1st, 3rd and 5th cycle was measured gravimetrically, and evaluated in relation to apparent amylose content (AAC) and distribution of amylopectin branch chains with degree of polymerization 6-12 (APC ratio). Syneresis was not observed for starch gels of cassava, normal and waxy japonica rice up to the 1st, 3rd and 5th cycle, respectively. On the other hand, syneresis rapidly occurred for starch gels of elephant yam, new cocoyam, potato, edible canna, and water yam. Optimal multiple linear regression models were generated to predict individual effect of AAC and APC ratio on syneresis of starch gels. The prediction models illustrated the positive unit-contribution of AAC and negative unit-contribution of APC ratio to syneresis (P < 0.001).     

Production and characterization of biopolyols and polyurethane foams from crude glycerol based liquefaction of soybean straw

The feasibility of using crude glycerol to liquefy soybean straw for the production of biopolyols and polyurethane (PU) foams was investigated in this study. Liquefaction conditions of 240 °C, >180 min, 3% sulfuric acid loading, and 10-15% biomass loading were preferred for the production of biopolyols with promising material properties. Biopolyols produced under preferential conditions showed hydroxyl numbers from 440 to 540 mg KOH/g, acid numbers below 5 mg KOH/g, and viscosities from 16 to 45 Pa.s. PU foams produced under preferential conditions showed densities from 0.033 to 0.037 g/cm³ and compressive strength from 148 to 227 kPa. These results suggest that crude glycerol can be used as an alternative solvent for the liquefaction of lignocellulosic biomass such as soybean straw for the production of biopolyols and PU foams. The produced biopolyols and PU foams showed material properties comparable to their analogs from petroleum solvent based liquefaction processes.     

Synthesis, structure and blue luminescent properties of a new silver(I) triazolate coordination polymer with 810-a topology

A novel 3D coordination polymer [Ag(dmtrz)] (dmtrz = 3,5-dimethyl-1,2,4-triazole) (1) was prepared under solvothermal condition and structurally characterized. The crystal structure reveals that Ag(I) centers are firstly linked via dmtrz anions to form an infinite 2₁ helix, which is further interconnected to four neighboring anti-parallel helices to form a 3D framework with rare non-interpenetrating 8²10-a topology.     

Cartilage aggrecan can undergo self-adhesion

Here it is reported that aggrecan, the highly negatively charged macromolecule in the cartilage extracellular matrix, undergoes Ca²⁺-mediated self-adhesion after static compression even in the presence of strong electrostatic repulsion in physiological-like solution conditions. Aggrecan was chemically end-attached onto gold-coated planar silicon substrates and gold-coated microspherical atomic force microscope probe tips (end radius R ≈ 2.5 μm) at a density (∼40 mg/mL) that simulates physiological conditions in the tissue (∼20-80 mg/mL). Colloidal force spectroscopy was employed to measure the adhesion between opposing aggrecan monolayers in NaCl (0.001-1.0 M) and NaCl + CaCl₂ ([Cl⁻] = 0.15 M, [Ca²⁺] = 0 - 75 mM) aqueous electrolyte solutions. Aggrecan self-adhesion was found to increase with increasing surface equilibration time upon compression (0-30 s). Hydrogen bonding and physical entanglements between the chondroitin sulfate-glycosaminoglycan side chains are proposed as important factors contributing to aggrecan self-adhesion. Self-adhesion was found to significantly increase with decreasing bath ionic strength (and hence, electrostatic double-layer repulsion), as well as increasing Ca²⁺ concentration due to the additional ion-bridging effects. It is hypothesized that aggrecan self-adhesion, and the macromolecular energy dissipation that results from this self-adhesion, could be important factors contributing to the self-assembled architecture and integrity of the cartilage extracellular matrix in vivo.     

The effect of citric acid on the structural properties and cytotoxicity of the polyvinyl alcohol/starch films when molding at high temperature

A series of starch/polyvinyl alcohol (PVA) films, denoted SP films, with varying concentrations (5–30 wt%) of citric acid (CA) were solvent cast at 140 °C. The effects of CA on the chemical structure, thermal properties, swelling degree, mechanical properties, crystallinity, and cytotoxicity were investigated. Fourier-transform infrared (FT-IR) spectroscopy showed that an esterification took place between CA and starch (or PVA) during molding at 140 °C. This esterification and the multi-carboxyl structure of CA resulted in a chemical cross-linking of the blended system. Furthermore, the esterification occurred more easily between starch and CA as opposed to between the PVA and CA. The residual-free CA acted as a plasticizer for the starch and PVA. As compared to the hydroxyl groups on glycerol, the carboxyl groups on CA were capable of forming stronger hydrogen bonds between CA and other components, and this cross-linking and strong hydrogen bonding enhanced the thermal stability of the SP films. Consequently, the water absorbance decreased from 33% to 20% as the CA percentage increased from 5 to 30 wt%. When 5 wt% CA was added, the tensile strength of the sample increased from 39 to 48 MPa, but when even more CA was added (from 5 to 30 wt%), the tensile strength decreased from 48 to 42 MPa and the elongation at break increased from 102% to 208%. This was caused by the plasticizing effect of the residual-free CA in the blend. The cell relative growth rates of samples with varying CA concentrations exceeded 80% after 7 days of incubation, and this demonstrated that there was no significant toxicity on the cells’ growth when the CA content was less than 20 wt%.     

Lysine reactivity and starch gelatinization in extruded and pelleted canine diets

Fifteen dry adult canine diets (i.e., dinners, extrudates, pellets) were collected from retailers in Wageningen, The Netherlands, and chemically and physically characterized. Quality measurements were lysine O-methylisourea (OMIU) reactivity and starch gelatinization degree (SGD). In general, extruded diets had a higher crude fat and starch content than pellets. Mean values for starch gelatinization were higher in pellets and ranged between 0.78 and 0.91. The mean reactive/total lysine ratio in extrudate samples was about 5–10% higher than in pellet samples, suggesting the presence in commercial diets of about 200 g bound lysine/kg in pellets and 120 g/kg in extrudates with bound lysine levels of canine dinners about 170 g/kg. Variation of analysed nutrients in pellets was larger than in extrudates. Inclusion of animal or vegetable ingredients, and the process variables during extrusion or pelleting, are the likely causative factors for the variation in lysine reactivity and starch gelatinization.