Microspheres and Nanoparticles

As discussed earlier, noncollagenous proteins, particularly albumin and to a lesser extent gelatin, in the form of microspheres and nanoparticles continue to be exploited as drug delivery systems. Oppen-heim (71) and Speiser (72) reviewed the technology developed to produce ultrafine particles, often referred to as nanoparticles. 

With these principles in mind, we refer the reader to valuable recent reviews, original reports, and discussions [65-68] of probes consisting of proteins, organic dyes, and nanoparticles such as quantum dots (QDs, [2, 68-77]) and other intriguing particles plastic microspheres and nanoparticles [78], multifunctional encoded particles [79], nanodisk codes [80], nano-flares [81], E-PEBBLES [82], C-dots [83], nanocrystal (NC)-encoded microbeads... 

Microspheres and nanoparticles often consist of biocompatible polymers and belong either to the soluble or the particle type carriers. Besides the aforementioned HPMA polymeric backbone, carriers have also been prepared using dextrans, ficoll, sepharose or poly-L-lysine as the main carrier body. More recently alginate nanoparticles have been described for the targeting of antisense oligonucleotides [28]. As with other polymeric carrier systems, the backbone can be modified with e.g. sugar molecules or antibody fragments to introduce cellular specificity. 

Besides parenteral application of microspheres and nanoparticles for cell selective delivery of drugs, they have more recently been studied for their application in oral delivery of peptides and peptidomimetics [30]. Immunological tolerance induction against beta-lac-toglobulin could be achieved by application of this protein in a poly-lactic-glycolide microsphere formulation [31]. 

Both microspheres and nanoparticles are retained within the eye for extended periods and provide slow, sustained release of the drags. Microparticulates for intraocular drag delivery have been formulated as ... 

Zimmer A, Kreuter J. Microspheres and nanoparticles used in ocular delivery systems. Adv. Drug DeUv. Rev. 1995 16 61-73. 

In spite of these formidable challenges, the attractiveness of oral route has fueled the exploration of an incredibly diverse set of strategies to deliver proteins and peptides and the subject has been exhaustively reviewed. The various approaches include permeation enhancers, enzyme inhibitors, mucoadhesives, multifunctional matrices that simultaneously incorporate the above strategies, enteric coatings that offer protection from the acidic environment of the stomach, encapsulation (liposomes, microspheres, and nanoparticles), pH-sensitive polymers, microemulsions, carriers (delivery agents), and protein modification either to simply enhance permeability or to exploit specific transporters. While proof-of-concept has been demonstrated with most of these delivery systems in animal... 

Pardeshi, S., Dhodapkar, R., Kumar, A. (2014). Molecularly Imprinted microspheres and nanoparticles prepared using precipitation polymerisation method for selective extraction of gallic acid from... 

In Table 9.3 are depicted recent examples of the most explored drug systems in the form of microspheres and nanoparticles using chitosan and derivatives in their formulation. 

Table 9.3 Some examples of the recent applications of chitosan in the formulation of microspheres and nanoparticles for several pharmaceutical applications.

K. Yoshimatsu, K. Reimhult, A. Krozer, K. Mosbach, K. Sode and L. Ye, Uniform molecularly imprinted microspheres and nanoparticles prepared by precipitation polymerization The control of particle size suitable for different analytical apphcations. Anal. Chim. Acta, 584(1) 112-121,2007. 

Controlled drug delivery (both localized and targeting systems), such as microspheres and nanoparticles. 

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