Effect of Formulation Factors and Oxygen Levels on the Stability of Aqueous Injectable Solution Containing Pemetrexed.

The aim of this study was to investigate the effects of various parameters at each control strategy in drug product degradation on the stability of pemetrexed in injectable aqueous solution. A forced degradation study confirmed that oxidation is the main mechanism responsible for the degradation of pemetrexed in aqueous solutions. As control strategies, the antioxidant levels, drug concentration, pH of the control formulation, dissolved oxygen (DO) levels in the control process, and headspace oxygen levels in the control packaging were varied, and their effects on the stability of pemetrexed were evaluated. Sodium sulfite was found to be particularly effective in preventing the color change, and N-acetylcysteine (NAC) had a significant effect in preventing chemical degradation. The sulfite and NAC were found to stabilize pemetrexed in the aqueous solution by acting as sacrificial reductants. A pH below 6 caused significant degradation. The stability of pemetrexed in the solution increased as the concentration of the drug increased from 12.5 to 50 mg/mL. In addition, the DO levels in the solution were controlled by nitrogen purging, and the oxygen levels in headspace were controlled by nitrogen headspace, which also had significant positive effects in improving the stability of the pemetrexed solution; thus, it was confirmed that molecular oxygen is involved in the rate-limiting oxidation step. Based on these results obtained by observing the effects of various control strategies, the optimal formulation of an injectable solution of pemetrexed is suggested as follows: sodium sulfite at 0.06 mg/mL, as an antioxidant for prevention of color change; NAC at 1.63 mg/mL, as an antioxidant for prevention of chemical degradation; pH range 7-8; DO levels below 1 ppm; and headspace oxygen levels below 1%. In conclusion, it can be suggested that this study, which includes well-designed control strategies, can lead to a better understanding of the complex degradation mechanism of pemetrexed; thus, it can lead to the development of an injectable solution formulation of pemetrexed, with improved stability.

Cross-linked hyaluronic acid-based flexible cell delivery system: application for chondrogenic differentiation.

A flexible porous three-dimensional (3D) matrix of hyaluronic acid (HA) was developed to improve the rigidity problems of the previously developed 3D systems. The viscoelasticity of the new formulation was expected to facilitate the differentiation of chondrocytes for the treatment of osteoarthritis (OA). The 3D matrix was fabricated using poly (ethylene glycol) diglycidyl ether (PEGDG) as a cross-linker, which was identified by Fourier transform infrared spectroscopy (FT-IR). The porous structure of the matrix was observed by scanning electron microscopy (SEM). The rheological characteristics of the fabricated HA matrix, that transforms to a gel-like semisolid state in the culture media with and without chondrocytes, were investigated. The proliferation of chondrocytes in the matrix increased according to the cultivation time. The chondrogenic differentiation of chondrocytes in the matrix also increased as determined by reverse transcription-polymerase chain reaction (RT-PCR) and by quantification of sulfated glycosaminoglycan (s-GAG). Moreover, safranin-O staining demonstrated that chondrocytes in the matrix produced extracellular matrix (ECM) after 28 days of culture. Thus, these results show that the "flexible" porous 3D cell delivery system based on HA could improve the clinical efficiency in OA treatment.

Development of a novel ophthalmic ciclosporin A-loaded nanosuspension using top-down media milling methods.

To develop a novel ciclosporin A (CsA)-loaded nanosuspension causing less ocular irritation, a range of nanosuspensions was prepared with various polymers using a media milling method. The effects of polymer, milling time, milling speed and bead material on the particle size of the nanosuspension were investigated. Stability and irritation tests in rabbits' eyes were then performed comparing the nanosuspension with a commercial product. Of the nanosuspensions prepared with various polymers, that with PVA showed no creaming or sedimentation phenomena and gave the smallest particles of about 530 nm. The particle size decreased abruptly as the milling time increased to 2 h and then hardly decreased further. As the milling speed was increased, the particle size of CsA in the nanosuspension also increased. Nanosuspensions prepared with zirconia beads gave significantly finer particles than those with polystyrene beads. In particular, the CsA-loaded nanosuspension with a CsA/PVA/water weight ratio of 0.5/1/100 prepared using the top-down media milling method with zirconia beads of 300 microm diameter at 1000 rpm for 2 h gave a minimum particle size of about 530 nm. This nansuspension was physcally and chemically stable for at least two months. In the Draize test, both this nanosuspension and the commercial product gave very slight ocular irritation. However, in the Schirmer tear test, this nanosuspension caused less irritation to the rabbits' eyes compared to the commercial product. Thus, the CsA-loaded nanosuspension prepared with PVA and water using the top-down media milling method could be a promising candidate for causing less ocular irritation.

Interpenetrating polymer network (IPN) scaffolds of sodium hyaluronate and sodium alginate for chondrocyte culture.

In this study, porous sodium hyaluronic acid/sodium alginate (HA/SA) scaffold based on interpenetrating polymeric network (IPN) technique has been fabricated, where HA and SA were cross-linked with poly(ethylene glycol) diglycidyl ether (PEGDG) and calcium chloride, respectively. The mean pore size and the swelling ratio of fabricated scaffolds decreased, and the compressive strength increased as the content of SA increased in HA/SA IPN scaffold. Rabbit chondrocytes were seeded within the HA/SA IPN scaffolds, and then their proliferation as well as chondrogenic differentiation was examined. DNA contents observed from the chondrocytes cultured in the IPN scaffolds increased with time over 21 days, which demonstrated that the rabbit chondrocytes continued to proliferate in HA/SA scaffolds. Results of the 1,9-dimethylmethylene blue (DMMB) and p-dimethylaminobenzaldehyde (DMBA) assays showed that glycosaminoglycan (s-GAG) and collagen contents increased over culture period, indicating the chondrogenic differentiation in the scaffold. Reverse transcription-polymerase chain reaction (RT-PCR) results showed the expression of type II collagen, the main chondrogenic differentiation marker. The bands indicating mRNA expression of type II collagen increased with the culture period. These results demonstrated that the porous HA/SA IPN scaffolds were successfully prepared and could serve as an effective delivery system of the three-dimensional culture of chondrocytes.