Modeling flow induced crystallization in film casting of polypropylene

Data from iPP film casting experiments served as a basis to model the effect of flow on polymer crystallization kinetics. These data describe the temperature, width, velocity and crystallinity distributions along the drawing direction under conditions permitting crystallization along the draw length. In order to model the effect of flow on crystallization kinetics, a modification of a previously defined quiescent kinetic model was adopted. This modification consisted in using a higher melting temperature than in the original quiescent model. The reason for the modification was to account for an increase of crystallization temperature due to entropy decrease of the flowing melt. This entropy decrease was calculated from the molecular orientation on the basis of rubber elasticity theory applied to the entangled and elongated melt. The evolution of molecular orientation (elongation) during the film casting experiments was calculated using a non-linear dumbbell model which considers the relaxation time, obtained from normal stress difference and viscosity functions, to be a function of the deformation rate. The comparison between experimental distributions and model based crystallinity distributions was satisfactory

Phenomenological and Formulation Aspects in Tailored Nanoliposome Production

Liposomes as cell‐mimetic system have attracted wide attention of researchers in various branches of the drug delivery topic as they can be highly functionalized and personalized, thus solving the major drawbacks of bioactive molecules linked to their low stability, limited membrane permeability, short half‐life and low bioavailability. The development of sustainable processes able to produce ad hoc liposomes in a rapid manner through the use of not‐laboured techniques, avoiding drastic conditions, is of great relevance for the industrial sector. In this chapter, two novel liposome production processes, the ultrasound‐assisted thin‐film hydration and the simil‐microfluidic techniques sharing the same size reduction/homogenization preparative step, are presented. The phenomenological aspects involved in vectors constitution through the duty cycle sonication process (bilayer rupture/vesicles formation mechanisms) and through the simil‐microfluidic approach (intubated flows interdiffusion mechanisms) are described. Finally, two applications as case histories involving the use of the developed techniques for relevant classes of active molecule delivery are described. In particular, a pharmaceutical application concerns the encapsulation of short‐interfering RNA (siRNA) molecule, used for gene therapy, inside cationic nanoliposomes, and a nutraceutical application consists in the production of ferrous sulphate anionic liposomal formulations with improved features compared to those already present on the market

Physiologically Based Pharmacokinetics: A Simple, All Purpose Model

To predict the drug hemeatic levels after administration is a goal of great interest in the design of novel pharmaceutical systems and in therapies management. The most reliable approach in pharmacokinetic modeling consists in analyzing the physiology of the living beings and in describing tissues and organs as different biochemical reactors. These models have been identified as physiologically based pharmacokinetic models (PBPK). They can be very detailed in the description, but, in this case, they also claim for the knowledge of an high number of parameters which are difficult to be determined by experiments. In this work, a review of the most complete PBPK models proposed in literature was performed, and a novel PBPK model was developed and validated by comparison with in vivo data available in the literature. The appeals of the novel model are its simplicity and the limited number of parameters required. Last but not least, it was proved able to predict the hemeatic drug levels after different kinds of administrations (intravenous injection, oral assumption of delayed release tablets)

Intensifying the microencapsulation process: Ultrasonic atomization as an innovative approach

In this review, new approaches to the microencapsulation processes, widely used in the manufacturing of pharmaceutical products, are discussed focusing the attention on the emerging ultrasonic atomization technique. Fundamentals and novel aspects are presented, and advantages of ultrasonic atomization in terms of intensification and low energy requests are emphasized

Anti-Osteoporotic Drug Release from Ordered Mesoporous Bioceramics: Experiments and Modeling

The release of a potent bone-resorption inhibitor such as zoledronate from a versatile drug delivery system such as SBA 15 has been modeled. The initial and boundary conditions have been defined, together with the system parameters, including the determination of equilibrium and transport parameters. Additionally, the experimental model of the same system has been observed to validate the prediction here developed. This approach represents a powerful tool for the designing of mesoporous implantable drug delivery systems because their release kinetics can be predicted in advance, and this leads to a considerable time and resources saving

Controlled drug release from hydrogel-based matrices: Experiments and modeling

Controlled release by oral administration is mainly achieved by pharmaceuticals based on hydrogels. Once swallowed, a matrix made of hydrogels experiences water up-take, swelling, drug dissolution and diffusion, polymer erosion. The detailed understanding and quantification of such a complex behavior is a mandatory prerequisite to the design of novel pharmaceuticals for controlled oral delivery. In this work, the behavior of hydrogel-based matrices has been investigated by means of several experimental techniques previously pointed out (gravimetric, and based on texture analysis); and then all the observed features were mathematically described using a physical model, defined and recently improved by our research group (based on balance equations, rate equations and swelling predictions). The agreement between the huge set of experimental data and the detailed calculations by the model is good, confirming the validity of both the experimental and the theoretical approaches

Single-Pot Semicontinuous Bench Scale Apparatus To Produce Microparticles

This work presents both the design of a novel process to produce microparticles with a shell−core structure and a bench scale apparatus purposely realized. The developed process was designed to respond to mandatory needs of process intensification. It involved the coupling of two emergent technologies: atomization assisted by ultrasonic energy and microwave heating. The former was used to atomize polymeric solutions; the latter was applied to stabilize the produced droplets by drying. Both operations were performed in the same vessel with the aim to have a single-pot process chamber and were carried out by a semicontinuous procedure. Basic design criteria and advantages of the ultrasonic−microwave coupled operations in the realized apparatus are presented and discussed. Results of testing and of operating runs to produce shell−core microparticles are also reported, emphasizing the main features of the produced particles