Design and characterization of highly porous curcumin loaded freeze-dried wafers for wound healing

The goal of this research was to evaluate the beneficial effects of topical curcumin loaded freeze-dried wafers in wound healing. Curcumin wafers were fabricated by cross-linking of chitosan with beta glycerophosphate under magnetic stirring. Composite wafers were prepared by the addition of sodium hyaluronate. Wafers were fabricated by freeze-drying technique. The resulted wafers were examined by naked eye and their dimensions were measured using a caliper. % Drug content, in-vitro release and % water uptake tests were conducted to characterize the fabricated wafers. Porosity testing, compressive mechanical behavior, morphological examination using scanning electron microscopy, thermal behavior using differential scanning calorimetry and Fourier transform infrared spectroscopy were all carried out on the optimized cross-linked wafers followed by their microbiological assays and cytotoxicity studies. The results showed that the optimized wafers possessed high water uptake capabilities while entertaining very high porosity levels (86-89%). Microbiological assay revealed the superiority of the selected curcumin wafers versus free curcumin in bacterial growth inhibition against Staphylococcus epidermidis and Staphylococcus aureus (MRSA) bacteria. The anti-inflammatory effects of the selected curcumin wafers were evaluated against pro-inflammatory cytokines. The results suggested that they were significantly better than free curcumin in lowering cytokines levels. To conclude, the obtained findings revealed that curcumin wafers offered a promising solution in the field of wound healing.

Influence of Glycerophosphate Salt Solubility on the Gelation Mechanism of Colloidal Chitosan Systems

Recently, thermosensitive chitosan systems have attracted the interest of many researchers due to their growing application potential. Nevertheless, the mechanism of the sol-gel phase transition is still being discussed, and the glycerophosphate salt role is ambiguous. The aim of the work is to analyze the possibility of the exclusive use of a non-sodium glycerophosphate salt and to determine its impact on the gelation conditions determined by rheological and turbidimetric measurements as well as the stability of the systems by measuring changes in the Zeta potential value. It was found that ensuring the same proportions of glycerophosphate ions differing in cation to amino groups present in chitosan chains, leads to obtaining systems significantly different in viscoelastic properties and phase transition conditions. It was clearly shown that the systems with the calcium glycerophosphate, the insoluble form of which may constitute additional aggregation nuclei, undergo the gelation the fastest. The use of magnesium glycerophosphate salt delays the gelation due to the heat-induced dissolution of the salt. Thus, it was unequivocally demonstrated that the formulation of the gelation mechanism of thermosensitive chitosan systems based solely on the concentration of glycerophosphate without discussing its type is incorrect.

In-Situ Forming pH and Thermosensitive Injectable Hydrogels to Stimulate Angiogenesis: Potential Candidates for Fast Bone Regeneration Applications

Biomaterials that promote angiogenesis are required for repair and regeneration of bone. In-situ formed injectable hydrogels functionalised with bioactive agents, facilitating angiogenesis have high demand for bone regeneration. In this study, pH and thermosensitive hydrogels based on chitosan (CS) and hydroxyapatite (HA) composite materials loaded with heparin (Hep) were investigated for their pro-angiogenic potential. Hydrogel formulations with varying Hep concentrations were prepared by sol-gel technique for these homogeneous solutions were neutralised with sodium bicarbonate (NaHCO3) at 4 °C. Solutions (CS/HA/Hep) constituted hydrogels setting at 37 °C which was initiated from surface in 5-10 minutes. Hydrogels were characterised by performing injectability, gelation, rheology, morphology, chemical and biological analyses. Hydrogel solutions facilitated manual dropwise injection from 21 Gauge which is highly used for orthopaedic and dental administrations, and the maximum injection force measured through 19 G needle (17.191 ± 2.296N) was convenient for manual injections. Angiogenesis tests were performed by an ex-ovo chick chorioallantoic membrane (CAM) assay by applying injectable solutions on CAM, which produced in situ hydrogels. Hydrogels induced microvascularity in CAM assay this was confirmed by histology analyses. Hydrogels with lower concentration of Hep showed more efficiency in pro-angiogenic response. Thereof, novel injectable hydrogels inducing angiogenesis (CS/HA/Hep) are potential candidates for bone regeneration and drug delivery applications.

Injectable Chitosan Scaffolds with Calcium β-Glycerophosphate as the Only Neutralizing Agent

The presented work describes the method of preparation of thermosensitive chitosan hydrogels using calcium β-glycerophosphate salt as the only pH neutralizing agent and supporting the crosslinking process. The presence of calcium ions instead of sodium ions is particularly important in the case of scaffolds in bone tissue engineering. Rheological and physicochemical properties of low concentrated chitosan solutions with the addition of calcium β-glycerophosphate were investigated using rotational rheometry techniques, Zeta potential (by electrophoresis), XPS, and SEM analysis together with an EDS detector. It was found to be possible to prepare colloidal solutions of chitosan containing only calcium β-glycerophosphate (without sodium ions) undergoing a sol-gel phase transition at the physiological temperature of the human body. It has also been shown that it is possible to further enrich the obtained cellular scaffolds with calcium ions. Using the addition of calcium carbonate, hydrogels with a physiological ratio of calcium to phosphorus (1.6–1.8):1 were obtained.

Thermosensitive chitosan gels containing calcium glycerophosphate

In this paper the properties of thermosensitive chitosan hydrogels, formulated with chitosan chloride with β-glycerophosphate disodium salt hydrate and chitosan chloride with β-glycerophosphate disodium salt hydrate enriched with calcium glycerophosphate, are presented. The study focused on the determination of the hydrogel structure after conditioning in water. The structure of the gels was investigated by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The crystallinity of the gel structure was determined by X-ray diffraction analysis (XRD) and the thermal effects were determined based on DSC thermograms.

In vitro and in vivo evaluation of porous chitosan electret membrane for bone regeneration

A porous chitosan electret membrane, possessing a three-dimensional porous structure and surface charges, was developed using thermally induced phase separation method and grid-controlled corona charging. Results showed that surface charge release of porous electret membrane could be altered by varying charging voltage. Rat osteoblasts adhered well, and cell proliferation and differentiation were enhanced by porous electret membrane compared to porous uncharged membrane. Furthermore, rabbit calvarial defects model demonstrated that porous electret membrane promoted bone regeneration more significantly than porous uncharged membrane. Therefore, the porous chitosan electret membrane might be a promising material for bone regeneration and bone tissue engineering applications.

Carbon nanotubes functionalized with folic acid attached via biomimetic peptide linker

AIM

Anchoring folic acid (FA) with a biomimetic peptidic linker resistant to proteolytic degradation to act as a homing device on functionalized carbon nanotubes.

MATERIALS & METHODS

Ethylenediamine was attached to oxidized multiwalled carbon nanotubes (MWNTs) using 4-(4,6-dimethoxy-[1,3,5]triazin-2-yl)-4-methylmorpholinium tetrafluoroborate. FA was coupled with 6-aminohexanoic acid and derivatives of β-alanine, affording four intermediates, which connected to the MWNTs via peptidic linkers of various lengths.

RESULTS

Biomimetic nanomaterials were produced with FA as a homing molecule. The structure and properties of the nanomaterials were analyzed, confirming the versatility of the peptides used as linkers.

CONCLUSION

Conjugates of FA attached to MWNTs via peptide linkers prepared from β-alanine residues are resistant to proteolytic degradation. Viability in colon cancer cells and normal colonocytes confirmed their lack of cytotoxicity.