The controlled delivery of drugs can be effectively obtained using systems based on hydrogels. Tablets, to be orally administered, represent the simplest and the most traditional dosage systems based on hydrogel. Their formulation and preparation require to mix and to compress, in proper ratios, various excipients, including a swellable polymer and a drug. Carriers for controlled release systems are usually cross-linked polymers able to form hydrogels that show peculiar release mechanisms, where both diffusion and tablet swelling play important roles.
Part of the book: Smart Drug Delivery System
In this chapter, the modern uses of hydrogels in pharmaceutical and biomedical applications are revised following an engineering point of view, i.e. focusing the attention on material properties and process conditions. The chapter discusses the applications following the increase in scale‐size. First, the nanoscale systems, i.e. hydrogel nanoparticles (HNPs), are analysed in terms of preparative approaches (polymerization methods and uses of preformed polymers) and with a brief mention of the future trends in the field. Secondly, systems based on hydrogel microparticles (HMPs) are examined following the same scheme (polymerization methods, uses of preformed polymers, a mention of novel and future trends). Thirdly, and last but not the least, the hydrogel‐based drug delivery systems (macroscopic HB‐DDSs) are presented, focusing in particular on tablets made of hydrogels, discussing the characterization methods and on the modelling approaches used to describe their behaviour. Other macroscopic systems are also discussed in brief. Even if the vastness of the field makes its discussion impossible in a single chapter, the presented material can be a good starting point to study the uses of hydrogels in pharmaceutical and biomedical sciences.
Part of the book: Emerging Concepts in Analysis and Applications of Hydrogels
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.
Part of the book: Liposomes
Granulation is a size-enlargement process by which small particles are bonded, by means of various techniques, in coherent and stable masses (granules), in which the original particles are still identifiable. In wet granulation processes, the powder particles are aggregated through the use of a liquid phase called binder. The main purposes of size-enlargement process of a powder or mixture of powders are to improve technological properties and/or to realize suitable forms of commercial products. A modern and rational approach in the production of granular structures with tailored features (in terms of size and size distribution, flowability, mechanical and release properties, etc.) requires a deep understanding of phenomena involved during granules formation. By this knowledge, suitable predictive tools can be developed with the aim to choose right process conditions to be used in developing new formulations by avoiding or reducing costs for new tests. In this chapter, after introductive notes on granulation process, the phenomenological aspects involved in the formation of the granules with respect to the main process parameters are presented by experimental demonstration. Possible mathematical approaches in the granulation process description are also presented and the one involving the population mass balances equations is detailed.
Part of the book: Granularity in Materials Science