Systemic delivery microparticles

The possibility of controlling the morphology of the product is relevant, especially in the forms of bio-polymer preparations and controlled delivery systems. Polymeric microparticles, fibers, or three-dimensional networks can be produced by tuning the operating variables. 

As for a formulation using another administration route, Leitner et al. developed a nasal delivery system of hGH [194] based on the thiomer polycarbophil-cysteine (PCP-Cys) in combination with the permeation mediator glutathione (GSH). Microparticles were prepared by dissolving PCP-Cys/GSH/hGH (7.5 1 1.5), PCP/ hGH (8.5 1.5), and mannitol/hGH (8.5 1.5) in demineralized water, followed by lyophilization and micronization. PCP-Cys/GSH/hGH and PCP/hGH microparticles showed a comparable size distribution (80% in the range of 4.8 to 23 pm) and swelled to almost four fold size in phosphate-buffered saline. Both formulations exhibited almost identical sustained drug release prohles. The intranasal administration of the PCP-Cys/GSH/hGH microparticulate formulation resulted in a relative bioavailability of 8.11%, which represents a three fold and a 3.3-fold improvement compared with that of PCP/hGH microparticles and mannitol/hGH powder, respectively. The nasal microparticulate formulation based on PCP-Cys/ GSH/hGH might represent a promising novel tool for the systemic delivery of hGH. 

Moreover, stearic acid is a common constituent in enteric coating for its plasticity and stability in stomach. Occasionally, it is used as binder agent especially in melt pelletization. In addition to be a traditional biomedical material, which has been used for thousands of years, stearic acid also plays an important role in newly developed drug delivery system, like microparticle dispersion system which is usually used for sustained drug delivery. Stearic acid is a vital ingredient candidate for nanoparticle and microsphere preparation. 

Although stearic acid is a traditional pharmaceutical auxiliary, we can also find its place in new drug delivery system, like microparticle dispersion system, which has been extensively studied in recent decades. 

This chapter is unique in that it describes the fabrication, characterization and current biological applications of pSi, whereas previous reviews have focused either solely on the formation and modification of pSi, or on pSi microparticles for the detection of chemical and biological compounds. In 1997, Canham produced a book entitled. Properties of Porous Silicon, which contained a collection of the physical and chemical properties of pSi. In this chapter, we include details of tested and visionary ideas on nanosized and microsized delivery systems, both of which are today emerging as powerful tools for the systemic delivery of therapeutic molecules and imaging agents for different biomedical applications, from... 

A large variety of drug delivery systems are described in the literature, such as liposomes (Torchilin, 2006), micro and nanoparticles (Kumar, 2000), polymeric micelles (Torchilin, 2006), nanocrystals (Muller et al., 2011), among others. Microparticles are usually classified as microcapsules or microspheres (Figure 8). Microspheres are matrix spherical microparticles where the drug may be located on the surface or dissolved into the matrix. Microcapsules are characterized as spherical particles more than Ipm containing a core substance (aqueous or lipid), normally lipid, and are used to deliver poor soluble molecules... 

W Im-Emsap, GA Brazeau, JW Simpkins, R Bodmeier. Sustained drug delivery of 17-/1 estradiol from injectable biodegradble in situ forming microparticles (ISM) system. AAPS PharmSci Supplement 2(4), AAPS Annual Meeting Abstracts, 2000. 

However, with respect to other delivery systems, microparticles could maintain their physicochemical characteristics unaltered for long periods, allowing long-term storage they can be administered through different ways (orally, intramuscularly, or subcutaneously), depending on their composition and they are suitable for industrial production [23,24],... 

As above reported, among microparticles, CLS have been proposed as a new type of fat-based encapsulation system developed for drug delivery of bioactive compounds. 

Jilek S, Merkle HP, Walter E (2005) DNA-loaded biodegradable microparticles as vaccine delivery systems and their interaction with dendritic cells. Adv Drug Deliv Rev 57 377-390... 

Wendorf J, Chesko J, Kazzaz J et al (2008) A comparison of anionic nanoparticles and microparticles as vaccine delivery systems. Hum Vaccin 4 44-49... 

Ohagan, D.T. et al., Biodegradable Microparticles as Controlled Release Antigen Delivery Systems, Immunology. 73, 239, 1991. 

Bio-nanomaterials are significantly different from traditional larger biomaterials (e g., implants or microparticles as mentioned earlier) in terms of their physical and biological properties. Due to their new set of biological and physical properties, bio-nanomaterials also show potential for use as therapeutics and in dmg delivery systems. For instance, Na and coworkers in 2007 used a bio-nanomaterial, heparin/... 

Another example of a delivery system based on microbubbles and ultrasound is the delivery of circulating microparticles (polymer latex beads) or fluorescent red blood cells outside of the capillaries into the surrounding tissues by the action of ultrasound on the co-injected Optison microbubbles [79]. Interestingly, polymer beads and red blood cells could be detected tens of micrometers away from the capillaries where the bubble destruction took place. This may imply that during rapid destruction of a microbubble in a very strong ultrasound field, adjacent microsphere beads in the bloodstream can be propelled deep into the surrounding tissues. 

Silva et al. (2006) studied starch-based microparticles as a novel strategy for tissue engineering applications. They developed starch-based microparticles, and evaluated them for bioactivity, cytotoxicity, ability to serve as substrates for cell adhesion, as well as their potential to be used as delivery systems either for anti-inflammatory agents or growth factors. Two starch-based materials were used for the development of starch-based particulate systems (1) a blend of starch and polylactic acid (SPLA) (50 50 w/w) and (2) a chemically modifled potato starch, Paselli II (Pa). Both materials enabled the synthesis of particulate systems, both polymer and composite (with BG 45S5). A simple solvent extraction method was employed for the synthesis of SPLA and SPLA/BG microparticles, while for Pa and Pa/BG... 

The amount of investigational work on the subject of formulation also needs further review and amplification. Basic formulation studies have suggested that proteins could be used to form drug delivery systems (e.g., microparticles) the interactions of proteins with phospholipids is of sufficient interest to justify a short chapter. 

The use of albumin microparticles as a drug delivery system was first suggested by Kramer (1974) and several methods for their production were subsequently developed (Gupta and Haung 1989). Most methods involved the application of emulsification methodology and factors involved in this process have been evaluated by a number of authors. However, studies of the in vitro disintegration process of protein microspheres, induced by the presence of protease enzymes in the environment, are limited (El-Samaligy and Rohdewald 1983). 

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