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Abstract: Supercritical fluid assisted atomization introduced by a hydrodynamic cavitation mixer (SAA-HCM) was used to prepare bovine serum albumin (BSA) microparticles. Water was used as the sole solvent. A hydrodynamic cavitation mixer was applied to improve mass transfer and achieve a continuous near-thermodynamic-equilibrium solubilization of SC-CO2 in the liquid solution. Under the different conditions, the prepared BSA microparticles had various morphologies, such as corrugated particles, smooth hollow spherical particles and cup particles, with particle diameters ranging from 0.3 to 5μm. The microparticle formation process was elucidated with the shell formation and central bubble mechanism. Compared to native BSA, BSA microparticles did not show significant change in primary structure, according to the results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The secondary structure of BSA was characterized by Fourier transform infrared spectroscopy (FT-IR). No new peaks were observed after SAA-HCM processing. In addition, the crystalline structure of the BSA microparticles was demonstrated to be amorphous because of the sudden supersaturation in the precipitation process. The SAA-HCM process is expected to be a promising technique for producing microparticles suitable for pulmonary delivery of therapeutic macromolecules. [ABSTRACT FROM AUTHOR]

Abstract: A hydrodynamic cavitation mixer (HCM) was introduced in the supercritical fluid assisted atomization (SAA) process to improve mass transfer. SAA-HCM resulted in a more homogenous primary droplet and, as a consequence, narrower particle size distributions. Levofloxacin hydrochloride (LH) being selected as a model drug, the effects of cavitation generator on morphology, size, and distribution of precipitated particles were evaluated. In addition, the influences of several process parameters, such as the feed ratio between CO2 and liquid solution, solute concentration, etc., were investigated in detail. Spherical amorphous micron-sized particles were obtained at different CO2-solution feed ratio and solute concentrations. In all cases, particles with diameters smaller than 2.1μm were produced. The SAA-HCM is expected to be a promising technique for producing microparticles suitable for pulmonary delivery in drug delivery applications. [Copyright &y& Elsevier]

Graphical abstract Highlights • Large pores increased in size with extended soaking time from 0.5 to 2 h. • Elongating holding time inceased mean size and decrease the density of large pores. • Pore size change patterns are distinct below and above 7 MPa intermediate pressure. • The pore growth profile in two-step depressurization sc-CO 2 foaming was unfolded. Abstract Bi-modal porous material is considered to have superior physical and tissue-inducing properties. This study reports on the fabrication of bi-modal porous poly(ε-caprolactone) (PCL) scaffolds using two-step depressurization supercritical CO 2 foaming process. In a single process, large pores over 100 μm nucleated in the slow depressurization step, and coalesced during holding stage; small pores below 40 μm were formed in the rapid depressurization step. Investigation on foaming parameters demonstrated that soaking time longer than 0.5 h was necessary to produce bi-modal pores. It was noted that the holding stage had a significant impact on the final pores. In particular, intermediate pressure would affect the plasticizing capabilities of CO 2 to increase (5–7 MPa) or decrease (7–12 MPa) pore size. In all, bi-modal porous PCL foams with around 80% porosity were produced, and this work provided a potential reference to efficient design of bone tissue engineering scaffolds. [ABSTRACT FROM AUTHOR]

Drug-loaded hydrogels with wound environment stimuli-responsive property can significantly promote wound healing and are widely applied in dressings. Two natural polymers, i.e. sodium alginate and sodium hyaluronate, were modified by 3-aminophenylboric acid and then cross-linked with polyvinyl alcohol to prepare ROS responsive hydrogels. Doxycycline hydrochloride was loaded onto hydrogels using supercritical solvent impregnation (SSI) technology, and the effects of immersion time, pressure and temperature on drug loading capacity (DLC) were investigated. DLC firstly increased and then decreased with the elevation of supercritical CO 2 pressure, and maximum value was up to 11 mg/g at 15 MPa and 50 °C. In the in vitro drug release study, doxycycline hydrochloride was controllably released from hydrogels for 10 h via the sensitivity of boronate ester bonds to ROS. This work expands the application of SSI in wound dressing, which provides a new approach for the design of composite hydrogel formulations with uniform drug distribution. [Display omitted] • ROS-responsive hydrogels were fabricated via crosslinking Alg-PBA, HA-PBA and PVA. • Doxy was loaded onto hydrogels using supercritical solution impregnation. • The dynamic mechanical properties of drug-loaded hydrogels can be adjusted. • Dug-loaded hydrogels exhibited excellent in vitro antibacterial properties. [ABSTRACT FROM AUTHOR]

Poly(ε-caprolactone) (PCL) is recently developed for bone tissue engineering applications due to its lasting degradation rate which matches the natural growth rate of a bone. In this work, batch foaming of PCL using supercritical CO 2 was employed, and the effects of processing variables, namely soaking time, foaming temperature and pressure, depressurization rate on the pore morphology and structure were studied in detail. Results demonstrated that morphologies and structures of pores were significantly distinct astride foaming temperature of 40 °C, which were characterized by melt-state foaming and solid-state foaming respectively. The dramatic reduction of melting temperature ( T m ) caused by the presence of supercritical CO 2 was found to be the key for this specific phenomenon. Above 40 °C, the enhanced melting of PCL caused by the reduction of T m led to wider pore size distribution, i.e. melt-state foaming, and the domino effect of variables on pore size was amplified; whilst below 40 °C the foams showed dense and small pore morphology, i.e. solid-state foaming. By tuning processing variables, scaffolds with diameter of 12.5 ± 0.1 to 344 ± 54 μm and porosity of 60.8 ± 3.2% to 83.4 ± 1.3% were fabricated. Furthermore, the interconnectivity of neat PCL scaffolds were mostly around 70%, which showed potential application in bone tissue engineering. [ABSTRACT FROM AUTHOR]