Multifunctional protein-encapsulated polycaprolactone scaffolds: Fabrication and in vitro assessment for tissue engineering

Here we demonstrate the use of a twin screw extrusion/spiral winding (TSESW) process to generate protein-encapsulated tissue engineering scaffolds. Bovine serum albumin (BSA) was distributed into PCL matrix using both wet and hot melt extrusion methods. The encapsulation efficiency and the time-dependent release rate, as well as the tertiary structure of BSA (via circular dichroism), were investigated as a function of processing method and conditions. Within the relatively narrow processing window of this demonstration study it was determined that the wet extrusion method gave rise to greater stability of the BSA on the basis of circular dichroism data. The rate of proliferation of human fetal osteoblast (hFOB) cells and the rate of mineral deposition were found to be greater for wet extruded scaffolds, presumably due to the important differences in surface topographies (smoother scaffold surfaces upon wet extrusion). Overall, these findings suggest that the twin screw extrusion/spiral winding (TSESW) process offers significant advantages and flexibility in generating a wide variety of non-cytotoxic tissue engineering scaffolds with controllable distributions of porosity, physical and chemical properties and protein concentrations that can be tailored for the specific requirements of each tissue engineering application.     

On the spontaneous encapsulation of proteins in carbon nanotubes

Biomolecules–carbon nanotube (CNT) interactions are of great importance in CNT-based drug delivery systems and biomedical devices. In this study, a spontaneous encapsulation of a globular protein into the CNT was observed through molecular dynamics simulation. The free energy of the system was found to be decreased after the encapsulation, which is the most fundamental reason for this spontaneous process. The system enthalpy decrease was found to make a dominant contribution to the free-energy change, and the system entropy increase also contributes to the spontaneous process. During the insertion, the protein makes a stepwise conformational change to maximize its affinity to the CNT walls as well as the protein–CNT interactions, mainly resulting in the deformation of the β-sheets in the protein. As a whole, the CNT was considered to attract protein molecules nonspecifically although the groups with high hydrophobicity and/or aromatic rings show great affinity.     

Traumatic injury to the oesophagus

This contribution focuses on perforation of the oesophagus and foreign bodies within the oesophagus.     

Pediatric tubular pulmonary heart valve from decellularized engineered tissue tubes

Pediatric patients account for a small portion of the heart valve replacements performed, but a pediatric pulmonary valve replacement with growth potential remains an unmet clinical need. Herein we report the first tubular heart valve made from two decellularized, engineered tissue tubes attached with absorbable sutures, which can meet this need, in principle. Engineered tissue tubes were fabricated by allowing ovine dermal fibroblasts to replace a sacrificial fibrin gel with an aligned, cell-produced collagenous matrix, which was subsequently decellularized. Previously, these engineered tubes became extensively recellularized following implantation into the sheep femoral artery. Thus, a tubular valve made from these tubes may be amenable to recellularization and, ideally, somatic growth.The suture line pattern generated three equi-spaced leaflets in the inner tube, which collapsed inward when exposed to back pressure, per tubular valve design. Valve testing was performed in a pulse duplicator system equipped with a secondary flow loop to allow for root distention. All tissue-engineered valves exhibited full leaflet opening and closing, minimal regurgitation (<5%), and low systolic pressure gradients (<2.5 mmHg) under pulmonary conditions. Valve performance was maintained under various trans-root pressure gradients and no tissue damage was evident after 2 million cycles of fatigue testing.     

Process‐Induced Phase Transformation of Berberine Chloride Hydrates

Berberine is a natural quaternary ammonium alkaloid used clinically in the chloride salt form for the treatment of diarrhea in many Asian countries. Although the hydrate formation of berberine chloride (BCl) is well documented, the associated mechanism and implications in pharmaceutical formulation have not been studied in detail. In this study, pure BCl dihydrate and BCl tetrahydrate were recrystallized from water and their phase transformation behaviors under defined conditions were investigated. Additionally, pharmacopoeial grade BCl material consisting predominantly of the dihydrate form was examined for potential phase changes when being subjected to a conventional wet granulation procedure for tablet production. Results from solubility measurements, thermal analysis, variable temperature‐powder X‐ray diffraction (VT‐PXRD), and variable temperature‐Fourier transform infrared spectroscopy (VT‐FTIR) confirmed the solid‐state interconversions between the tetrahydrate and dihydrate at 30–49°C and between the dihydrate and anhydrate at 70–87°C. Consistent with the observed phase changes of the two pure hydrates, wet massing of the pharmacopoeial grade BCl sample led to a thermodynamics‐driven transition to the tetrahydrate form at room temperature while subsequent tray drying at 50°C caused a reversion back to the dihydrate form. The rate and extent of such hydrate conversion depended largely on the water activity of the granulated powder matrix, which in turn was governed by the particular excipients employed. The present findings have important implications in the regulation of the hydrate forms of BCl in the finished products using specific excipients. © 2009 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 1942–1954, 2010