Digital holography as 3D tracking tool for assessing acoustophoretic particle manipulation.

The integration of digital holography (DH) imaging and the acoustic manipulation of micro-particles in a microfluidic environment is investigated. The ability of DH to provide efficient 3D tracking of particles inside a microfluidic channel is exploited to measure the position of multiple objects moving under the effect of stationary ultrasound pressure fields. The axial displacement provides a direct verification of the numerically computed positions of the standing wave's node, while the particles' transversal movement highlights the presence of nodes in the planar direction. Moreover, DH is used to follow the aggregation dynamics of trapped spheres in such nodes by using aggregation rate metrics.

Modulation of drug release from hydrogels by using cyclodextrins: the case of nicardipine/beta-cyclodextrin system in crosslinked polyethylenglycol.

A simple approach is presented to modulate drug delivery from swellable systems by using complexants. The effect of complexants has been interpreted by means of simple mass balances on diffusing species and the involved relevant parameters have been individuated. The application of this strategy to the release of nicardipine (NIC) from swellable systems by using beta-cyclodextrin (CD) as complexant has evidenced the potential of the approach to tailor drug release. Crosslinked polyethyleneglycol has been synthesized, characterized and used as the swellable matrix. Swelling kinetics, NIC and CD diffusivities in the swollen matrix and NIC/CD phase solubility studies have been performed. The polymer matrix has been loaded with pure NIC or with NIC and CD at different ratios and release kinetics evaluated. Release profiles have shown that the presence of CD significantly affected drug delivery by decreasing the effective diffusivity of NIC. The higher the CD/NIC ratio the slower is the release. This effect has been interpreted on the basis of the proposed model and physically sound assumptions.

Water soluble drug delivery systems based on a non-biological bioadhesive polymeric system.

Matrix properties and release behaviour of monolithic devices based on a water soluble polymer has been investigated. Polyethyleneoxides of different molecular weights have been used and different molecular weight fractions have been blended in order to tune the release mechanism. Drug release kinetics have been closely related to swelling and dissolution properties of the adopted matrices. In particular the development of the external swollen layer of the tablet as well as the kinetic of dissolution have been monitored. The different drug delivery behaviours observed were related to the different matrix properties. Viscoelastic properties of the matrices have been also investigated. In fact, in order to obtain effective bioadhesive drug release devices, apart from the intrinsic mucoadhesive capabilities of the used polymers, also the viscoelastic properties of the water-polymer gel must also be taken into account. A good interpenetration between the adjacent layers of the mucus and the polymer gel is ineffective in holding the mucoadhesive tablet at a specific site if the polymer gel does not have a proper viscoelastic behaviour. The best compromise between good release, viscoelatic and mucoadhesive properties was obtained in the case of 50% by weight blend of the two adopted polymer fractions (600,000 and 4,000,000 molecular weight).

Poly(ethylene oxide) (PEO) and different molecular weight PEO blends monolithic devices for drug release.

An interpretation of the drug release from monolithic water-swellable and soluble polymer tablets is presented. A convenient parameter, alpha, which compares the drug-diffusive conductance in the gel layer with the swelling and dissolving characteristics of the unpenetrated polymer was used to describe the release behaviour of beta-hydroxyethyl-theophylline (etofylline) from compression-moulded tablets of hydrophilic pure semicrystalline poly(ethylene oxides) of mol wt 600,000 and 4,000,000 and of two blends of the two molecular weights of poly(ethylene oxides). The water swelling and dissolution characteristics of two polymers and two blends were analysed, monitoring the thickness increase of the surface-dissolving layer and the rates of water swelling and penetration in the tablets. The drug diffusivities in the water-penetrated polymer gels were measured by carrying out permeation tests. Finally, drug release tests were performed to investigate the release kinetics of the different systems in an aqueous environment at 37 degrees C. The drug release from the high molecular weight poly(ethylene oxide) is principally related to the material swelling rather than polymer dissolution, leading to a progressive decrease of the drug's diffusive conductance in the growing swollen layer, and hence to a non-constant release induced by the prevailing diffusive control. Conversely, drug release from the low molecular weight poly(ethylene oxide) is strictly related to the polymer dissolution mechanism. The achievement of stationary conditions, in which the rate of swelling equals the rate of dissolution, ensures a constant release rate, even in the case of very low drug-diffusive conductance in the external gel layer. Intermediate behaviours were detected in the case of the two blends.