Development of silver nanoparticles‐loaded calcium alginate beads embedded in gelatin scaffolds for use as wound dressings

Silver nanoparticles (AgNPs)‐loaded calcium alginate beads embedded in gelatin scaffolds were developed to sustain and maintain the release of silver (Ag⁺) ions over an extended time period. The UV irradiation technique was used to reduce Ag⁺ ions in alginate solution to AgNPs. The average sizes of AgNPs ranged between ca 20 and ca 22 nm. The AgNPs‐loaded calcium alginate beads were prepared by electrospraying of a sodium alginate solution containing AgNPs into calcium chloride (CaCl₂) solution. The AgNPs‐loaded calcium alginate beads were then embedded into gelatin scaffolds. The release characteristics of Ag⁺ ions from both the AgNPs‐loaded calcium alginate beads and the AgNPs‐loaded calcium alginate beads embedded in gelatin scaffolds were determined in either deionized water or phosphate buffer solution at 37 °C for 7 days. Moreover, the AgNPs‐loaded calcium alginate beads embedded in gelatin scaffolds were tested for their antibacterial activity and cytotoxicity. © 2014 Society of Chemical Industry     

Physical and light oxidative properties of eugenol encapsulated by molecular inclusion and emulsion–diffusion method

The aim of this research was to study the encapsulation of eugenol as a volatile active substance by inclusion with β-cyclodextrin (β-CD) and 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD), and by an emulsion–diffusion method with polycaprolactone (PCL). After formulation of each type of complex, size, zeta-potential, and thermal properties were determined by using Nanosizer®, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Overall, the mean sizes of encapsulated eugenol were the same at 320 nm. However, the size distribution of the β-CD and 2-HP-β-CD inclusion complex was poly-disperse as compared with eugenol encapsulated with polycaprolactone (PCL). TGA analysis revealed the encapsulation efficiency of PCL, β-CD eugenol and 2-HP-β-CD eugenol inclusion complexes were 100%, 90.9% and 89.1%, respectively. The study of oxidation stability revealed the emulsion–diffusion method was more efficient than the molecular inclusion method resulting from high stability depending on storage time. On the other hand, β-CD was more effective than 2-HP-β-CD for eugenol encapsulation. It is supposed that the side chain of hydroxypropyl group of 2-HP-β-CD might interrupt eugenol inclusion within the cavity of 2-HP-β-CD molecule. From our experiments, we concluded that the emulsion–diffusion method was the most effective for eugenol encapsulation to protect from light oxidation during storage time due to their complete wrapping of eugenol by PCL layer from TEM analysis.     

Physical characteristics of fish oil encapsulated by β-cyclodextrin using an aggregation method or polycaprolactone using an emulsion–diffusion method

Fish oils have many dietary benefits, but have strong odours and are easily oxidised. For these reasons, β-cyclodextrin (β-CD) a water-soluble polymer and polycaprolactone (PCL) a water-insoluble polymer were used to encapsulate fish oil in this study. In addition, the stabilities of freeze-dried fish oil (FO) in encapsulated complexes were investigated to determine fish oil release rates at different relative humidities and storage temperatures. In order to facilitate the practical applications of the water-soluble and insoluble fish oil complexes produced, release studies of fish oil were performed in de-ionised water, NaCl solution and fish sauce. Based on our studies, fish oil loaded β-CD at a mixing ratio of 10:20 (β-CD:FO (w:w)) was the best composition in terms of encapsulation efficiency (84.1%), fish oil loading (62.7%), fish oil leakage after freeze-drying (11.0%), and eicopentaenoic acid (EPA) encapsulation efficiency (6.5%). In addition, fish oil release rates from β-CD particles were slower in de-ionised water and in 15% and 25% NaCl than in fish sauce at all mixing ratios between β-CD and FO. The storage stabilities of freeze-dried β-CD–FO complexes at 10:20 (w:w) mixing ratio at various relative humidities retained 97% of fish oil within the particles during 3 days. However, the release rate of fish oil from β-CD–FO complexes of 10:20 mixing ratio was accelerated in fish sauce. In terms of the emulsion–diffusion method, PCL more efficiently retarded the release of FO in liquid or powder form, although particles were broken by freeze-drying. It is supposed that PCL better protected FO because of its water insolubility.     

The effect of cetyl palmitate crystallinity on physical properties of gamma-oryzanol encapsulated in solid lipid nanoparticles

This present study was aimed at investigating the effect of the crystallinity of cetyl palmitate based solid lipid nanoparticles (SLNs) on the physical properties of γ-oryzanol-loaded SLNs. SLNs consisting of varying ratios of cetyl palmitate and γ-oryzanol were prepared. Their hydrodynamic diameters were in the range 210-280?nm and the zeta potentials were in the range -27 to -35?mV. The size of SLNs increased as the amount of cetyl palmitate decreased whereas no significant change of zeta potentials was found. Atomic force microscopy pictures indicated the presence of disc-like particles. The crystallinity of SLNs, determined by differential scanning calorimetry and powder x-ray diffraction, was directly dependent on the ratio of cetyl palmitate to γ-oryzanol and decreased with decreasing cetyl palmitate content in the lipid matrix. Varying this ratio in the lipid mix resulted in a shift in the melting temperature and enthalpy, although the SLN structure remained unchanged as an orthorhombic lamellar lattice. This has been attributed to a potential inhibition by γ-oryzanol during lipid crystal growth as well as a less ordered structure of the SLNs. The results revealed that the crystallinity of the SLNs was mainly dependent on the solid lipid, and that the crystallinity has an important impact on the physical characteristics of active-loaded SLNs.     

The effect of the degree of deacetylation of chitosan on its dispersion of carbon nanotubes

The effect of the degree of deacetylation (DD) of chitosan biopolymer on the noncovalent surface modification of multiwall carbon nanotubes (MWCNTs) is presented. MWCNTs were modified by chitosan having different degree of deacetylation (61%, 71%, 78%, 84%, 90% and 93%) and UV-Visible spectroscopy was used to evaluate their dispersion efficiency as a function of chitosan concentration and degree of deacetylation. Results showed that the dispersion of MWCNTs could be dramatically improved when using chitosan with the lowest degree of deacetylation (61%DD) possibly due to a higher surface coverage of the MWCNTs. Zeta potential measurements were used to confirm that the chitosan surface coverage on the MWCNTs was twice as high when modifying the nanotubes surface with the 61%DD than when using the 93%DD chitosan. These results suggest that the dispersion of MWCNTs with chitosan can be improved when using chitosan having a degree of deacetylation of 61%. These results are of interest in particular for the improved dispersion of MWCNTs in aqueous solutions such as in drug delivery applications.     

Porous silicon confers bioactivity to polycaprolactone composites in vitro

Silicon is an essential element for healthy bone development and supplementation with its bioavailable form (silicic acid) leads to enhancement of osteogenesis both in vivo and in vitro. Porous silicon (pSi) is a novel material with emerging applications in opto-electronics and drug delivery which dissolves to yield silicic acid as the sole degradation product, allowing the specific importance of soluble silicates for biomaterials to be investigated in isolation without the elution of other ionic species. Using polycaprolactone as a bioresorbable carrier for porous silicon microparticles, we found that composites containing pSi yielded more than twice the amount of bioavailable silicic acid than composites containing the same mass of 45S5 Bioglass. When incubated in a simulated body fluid, the addition of pSi to polycaprolactone significantly increased the deposition of calcium phosphate. Interestingly, the apatites formed had a Ca:P ratio directly proportional to the silicic acid concentration, indicating that silicon-substituted hydroxyapatites were being spontaneously formed as a first order reaction. Primary human osteoblasts cultured on the surface of the composite exhibited peak alkaline phosphatase activity at day 14, with a proportional relationship between pSi content and both osteoblast proliferation and collagen production over 4 weeks. Culturing the composite with J744A.1 murine macrophages demonstrated that porous silicon does not elicit an immune response and may even inhibit it. Porous silicon may therefore be an important next generation biomaterial with unique properties for applications in orthopaedic tissue engineering.     

Effect of high‐pressure microfluidization on the structure of cassava starch granule

Microfluidization has been applied to modify starch granules. The study was conducted to investigate the effect of microfluidization on the structure and thermal properties of cassava starch–water suspension (20% w/w). The means of optical microscopy, SEM, FTIR spectroscopy, XRD, and DSC were applied to analyze the changes in microstructure, crystallinity, and thermal property. Microscopy observations revealed that native starch granules were oval, round, and truncated in shape. After the microfluidization treatment, a bigger starch granule was partially gelatinized, and a gel‐like structure was formed on a granular surface. No significant difference in XRD patterns of the samples were observed and all samples exhibited A‐type allomorph. Crystallinity decreased with the pressure. Sample treated at 150 MPa contains 17.1% crystalline glucan polymer, lower than that of native granules which have crystallinity of about 25.8%. A lower crystallinity means poor order of crystalline glucan polymer structure in starch granules. The disruption of crystalline order within the granule was also observed by FTIR measurement. Thermal analysis using DSC indicated that the microfluidization treatment brought about a significant decrease of melting enthalpy. The gelatinization enthalpy was 12.0 and 3.0 J/g for the native sample and samples treated under the 150 MPa, respectively. The results indicate that high‐pressure microfluidization process induced the gelatinization of cassava starch, which is evaluated by a percentage of the degree of gelatinization, due to a pronounced decrease with increasing microfluidizing pressure.     

J. Cosmet. Sci., 59, 233–242 (May/June 2008) Electrospun poly (vinyl alcohol) fiber mats as carriers for extracts from the fruit hull of mangosteen

Electrospinning is a process used to produce ultrafine fibers with diameters in the nanometer range. Electrospun fiber mats have high potentials for biomedical uses, due to their high surface area and ease of drug incorporation into the fibers. They can be used as carriers for drug delivery and can enhance drug release and skin permeability. The aim of this study was to prepare electrospun fiber mats and to incorporate extracts from the fruit hull of mangosteen. Anti-oxidant activity and extract release were determined and compared between the extract incorporated in the electrospun fiber mats and in the cast films. Poly (vinyl alcohol) (PVA) was selected as the polymer matrix. Extracts in the amount of 2.5%, 5%, and 10% w/w, based on the weight of PVA, were incorporated with 10% w/w PVA to finally obtain electrospun fiber mats and cast films. The extract content was evaluated by anti-oxidative activity using the 2,2-diphenyl-1picryhydrazyl (DPPH) method. The morphology of the electrospun fiber mats was analyzed using a scanning electron microscope (SEM). The results showed that the diameters of the fibers were in nanoscales and that no crystal of the extract was found at any concentration of the extract. The extract contents in the electrospun fiber mats prepared at 2.5%, 5%, and 10% w/w of the extract were 9.6%, 9.7%, and 10.8% of the initial loading concentration, respectively, whereas, those in the cast films were 23.9%, 14.5%, and 21.0%, respectively. The release of the extract from the electrospun fiber mats prepared at 2.5%, 5%, and 10% w/w of the extract at 120 min were 73.2%, 83.6%, and 81.3% w/w, respectively. However, much slower release from the cast films was observed (i.e. 4.3%, 29.1%, and 40.8% w/w, respectively).     

Process optimization of electrospun silk fibroin fiber mat for accelerated wound healing

Considering the outstanding biocompatibility of Bombyx mori silk fibroin, this study is designed to fabricate biomimetic nanofibrous structure made of silk fibroin, which can enhance cell activities for tissue formation. The electrospinning of blend of silk fibroin with low molecular weight poly(ethylene‐oxide) (PEO) is explored with ease of preparation for high productivities. The average diameter of electrospun silk fibroin (eSF) is decreased from 414 ± 73 to 290 ± 46 nm after PEO extraction. To induce the desired cellular activity, the surface of the eSF fibers is modified with fibronectin by using the carbodiimide chemistry method. The potential use of the obtained wound healing material is assessed by indirect cytotoxicity evaluation on normal human dermal fibroblast (NHDF) in terms of their attachment and cell proliferation. The surface‐modified eSF nanofiber mats show good support for cellular adhesion and spreading as a result of fibronectin grafting on the fiber surface, especially for cell migration inside the fibrous structure. These results demonstrate a new fabrication technique of surface‐modified silk fibroin electrospun nanofibers for biomedical application; with the ability to accelerate wound healing. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3634–3644, 2013     

The loss of OSA‐modified starch emulsifier property during the high‐pressure homogeniser and encapsulation of multi‐flavour bergamot oil by spray drying

The encapsulation of bergamot oil by spray drying was investigated by using octenyl succinylated waxy maize starch as wall material and bergamot oil as core. The bergamot oil is majorly composed of d‐limonene, linalool and linalyl acetate. High‐speed and high‐pressure homogenisers were used as major tools of emulsification process. The results indicated that some chemical functional groups were lost during the high‐pressure homogenisation. Moreover, larger emulsion droplet size (5–10 μm) was observed when emulsion passed through high‐pressure homogeniser. Meanwhile, the saturation of carrier solution before preparing the emulsion was also important to produce the encapsulated flavour powder by spray drying. The optimal value of air inlet temperature at 160 °C to give the highest flavour retention and the lowest surface oil content was observed. Furthermore, the retention of linalool after spray drying was higher than 100%. The transformation of each flavour might occur.