Drug delivery loading/release

Kwon, G., M. Naito, M. Yokoyama, T. Okano, Y. Sakurai, and K. Karaoka. 1997. Block copolymer micelles for drug delivery loading and release of doxorubidnControl. Rel. 48 195-201. 

Salonen J, Laitinen L, Kaukonen AM, Tuura J, Bjorkqvist M, Heikkila T, Vaha-Heikkila K, Hirvonen J, Lehto VP (2005) Mesoporous silicon microparticles for oral drug delivery loading and release of five model drugs. J Control Release 108 362-374... 

De TK, Hoffman AS (2001) A reverse microemulsion polymaization method for neparation of bioadhesive polyacrylic acid nanoparticles for mucosal drug delivery loading and release of timolol maleate. Attif Cells Blood Substit Immobil Biotechnol 29(l) 31-46... 

Figure 3 shows the amount of theophylline released at time t (Mt) relative to the total amount loaded (Moo) (i.e., Mt/Mco) as a function of time. Evidently theophylline-loaded PDMAAm-i-PIB networks are efficient drug delivery systems, and nearly complete release requires 24 hours. 

Concerning drug delivery, electrically erodible polymer gels for controlled release of drugs have been prepared, and a measured release rate of insulin has been observed under electrical stimulus [69]. A suspension of zinc insulin in a mixed solution of poly(ethyloxazoline) and PMAA was formed into a gel by decreasing the pH of the suspension. The obtained complex gel with 0.5 wt% of insulin was attached to a woven platinum wire cathode which was 1 cm away from the anode and immersed in 0.9% saline solution. When a stepped function of electrical current of 5 mA was applied to the insulin-loaded gel matrix, insulin was released in a stepwise manner up to a release of 70%. The insulin rate measured was 0.10 mg/h. 

Polymeric membrane-based implantable drug delivery systems have been developed to deliver growth hormone, hormonal contraception, and leuprolide for the treatment of prostate cancer. Implanted sialic tubes loaded with lev-onorgestrel Norplant system) is used outside the United States to provide five years of sufficient sustained release of the... 

Figure 4.1 Released amount Qt versus square-root-time -Jt plots. Illustration of loading less than or equal to saturation (dispersed, A < Cs) and greater than saturation (dissolved, A > Cs) in a matrix-type diffusion-controlled drug delivery system.

Polyphosphazenes are a relatively new class of biodegradable polymers. Their hydrolytic stability or instability is determined not by changes in the backbone structure but by changes in the side groups attached to an unconventional macromolecular backbone. Synthetic flexibility and versatile adaptability of polyphosphazenes make them unique for drug delivery applications. For example, Veronese et al.18 prepared polyphos-phazene microspheres with phenylalanine ethyl ester as a phosphorous substituent and loaded it with succinylsulphathiazole or naproxen. The kinetics of release from these matrices were very convenient in yielding local concentrations of the two drugs that are useful per se or when mixed with hydroxyapatite for better bone formation. Polyphosphazene matrices are also considered as potential vehicles for the delivery of proteins and vaccines.19... 

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