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Forced degradation is a method of studying the stability of pharmaceuticals in order to design stable formulations and predict drug product shelf life. Traditional methods of reaction and analysis usually take multiple days, and include LC-UV and LC-MS product analysis. In this study, the reaction/analysis sequence was accelerated to be completed within minutes using Leidenfrost droplets as reactors (acceleration factor: 23-188) and nanoelectrospray ionization MS analysis. The Leidenfrost droplets underwent the same reactions as seen in traditional bulk solution experiments for three chemical degradations studied. This combined method of accelerated reaction and analysis has the potential to be extended to forced degradation of other pharmaceuticals and to drug formulations. Control of reaction rate and yield is achieved by manipulating droplet size, levitation time and whether or not make-up solvent is added. Evidence is provided that interfacial effects contribute to rate acceleration.

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The structure of Chinese bituminous Zao Zhuang coal was carefully evaluated on the basis of information from NMR, pyrolysis, ruthenium-catalyzed oxidation reaction (RICO), and single coal particle solvent swelling methods. This coal and its SRC liquefaction fractions show good coking property so that the pyrolysis is accompanied by a lot of coke, this being less useful for its structural elucidation than the case of Japanese Akabira coal. The pretreatment of this coal by the ether bond cleavage reaction can increase volatile-comprising molecules that when recognized provide valuable information on molecular constituents of the coal. SPE/MAS 13 C NMR and CP-DD (dipolar dephasing)/MAS 13 C NMR techniques were used to assess carbon distribution. The RICO reaction offered information regarding aliphatic functionalities and bridge types and also suggested the presence of some types of molecular units. Solvent swelling experiments implied that this coal has, on average, relatively low cross-link density and verified the structural heterogeneity of the coal. By using the data from the analytical techniques given above, a model structure of Zao Zhuang coal consisting of one MS, one PS, and two PI structures was constructed. The proposed structure is in keeping with various aspects of its reactivity.

Biodegradable polymeric scaffolds have been widely used in tissue engineering as a platform for cell proliferation and subsequent tissue regeneration. Conventional microextrusion methods for three-dimensional (3D) scaffold fabrication were limited by their low resolution. Electrospinning, a form of electrohydrodynamic (EHD) printing, is an attractive method due to its capability of fabricating high-resolution scaffolds at the nanometer/micrometer scale level. However, the scaffold was composed of randomly orientated filaments which could not guide the cells in a specific direction. Furthermore, the pores of the electrospun scaffold were small, thus preventing cell infiltration. In this study, an alternative EHD jet printing (E-jetting) technique has been developed and employed to fabricate 3D polycaprolactone (PCL) scaffolds with desired filament orientation and pore size. The effect of PCL solution concentration was evaluated. Results showed that solidified filaments were achieved at concentration >70% (w/v). Uniform filaments of diameter 20 μm were produced via the E-jetting technique, and X-ray diffraction and attenuated total reflectance Fourier transform infrared spectroscopic analyses revealed that there was no physicochemical changes toward PCL. Scaffold with a pore size of 450 μm and porosity level of 92%, was achieved. A preliminary in vitro study illustrated that live chondrocytes were attaching on the outer and inner surfaces of collagen-coated E-jetted PCL scaffolds. E-jetted scaffolds increased chondrocytes extracellular matrix secretion, and newly formed matrices from chondrocytes contributed significantly to the mechanical strength of the scaffolds. All these results suggested that E-jetting is an alternative scaffold fabrication technique, which has the capability to construct 3D scaffolds with aligned filaments and large pore sizes for tissue engineering applications.

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