Drugs controlled release

Another important application of boronic acid-containing hydrogel is for drug release. The porous structure of hydrogels allows for loading of drugs into the gel matrix. In addition, their stimuli-responsivity allows for fine control over the drug release rate. 

We recently demonstrated a new method to release drugs from boronic acid-based hydrogel films. Because of the reversible/dynamic nature of 

The generation of porous topographic substrates by inirnicking the native extracellular matrix to promote the regeneration of damaged bone tissues, is a rather challenging process (23). 

Scaffolds that have been developed for bone tissue regeneration support bone cell growth and induce bone-forming ceUs by natural proteins and growth factors. Several issues of these materials are improper scaffold stability, insufficient ceU adhesion, proliferation, and differentiation. For these reasons, the use of engineered nanoparticles is of interest in bone tissue engineering applications. 

Electrospraying is advantageous in comparison to other methods, as it generates nanomaterials of particle sizes in the microscale 

These nanomaterials can be extensively used as therapeutic agents and for drug delivery. The controlled and sustained release of encapsulated drugs, proteins, vaccines, growth factors, cells, and nucleotides from nanoparticles has been weU developed in the field of nanomedicine. These topics have been reviewed (23). 

Tarik Arafat, I. Gibson, and X. Li, Rapid Prototyping Journal, Vol. 20, 

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Heller, J., Controlled drug release from poly(ortho esters) A surface eroding polymer, J. Control. Rel., 2, 167-177, 1985. 

Reis MAA, Sinisterra RO, Belchior JC. An alternative approach based on artificial neural networks to study controlled drug release. J Pharm Sci 2004 93 418-28. 

In particular, rotaxane dendrimers capable of reversible binding of ring and rod components, such as Type II, pseudorotaxane-terminated dendrimers, can be reversibly controlled by external stimuli, such as the solvent composition, temperature, and pH, to change their structure and properties. This has profound implications in diverse applications, for instance in the controlled drug release. A trapped guest molecule within a closed dendrimeric host system can be unleashed in a controlled manner by manipulating these external factors. In the type III-B rotaxane dendrimers, external stimuli can result in perturbations of the interlocked mechanical bonds. This behavior can be gainfully exploited to construct controlled molecular machines. 

Noteable are recent studies on the generation of polymer particles as carriers for controlled drug release [333] and of cationic solid lipid micro-particles as synthetic carriers for the targeted delivery of macromolecules to phagocytic antigen-presenting cells [334]. The industrial interest, although rarely disclosed, is evident from the patents filed in the field (see, e.g., [335, 336]). 

H. Goodman and G. Banker. Molecular-scale drug entrapment as a precise method of controlled drug release I Entrapment of cationic drugs by Polymeric flocculation, J. Pharm. Sci. 59 1131-1137, 1970. 

A reported application of canonical analysis involved a novel combination of the canonical form of the regression equation with a computer-aided grid search technique to optimize controlled drug release from a pellet system prepared by extrusion and spheronization [28,29]. Formulation factors were used as independent variables, and in vitro dissolution was the main response, or dependent variable. Both a minimum and a maximum drug release rate was predicted and verified by preparation and testing of the predicted formulations. Excellent agreement between the predicted values and the actual values was evident for the four-component pellet system in this study. 

SY Ng, T Vandamme, MS Taylor, J Heller. Controlled drug release from self-catalyzed poly(ortho esters). Ann NY Acad Sci 831 168-178, 1997. 

Fig. 4.27 Controlled drug release and delivery system using colloid capping of a mesoporous silica channel. Reprinted with permission from [222], C.-Y. Lai etal.J. Am. Chem. Soc. 2003, 725, 4451. 2003, American Chemical Society.

Template synthesized silica nanotubes (SNTs) provide unique features such as end functionalization to control drug release, inner voids for loading biomolecules, and distinctive inner and outer surfaces that can be differentially functionalized for targeting and biocompatibility.50 A general path to synthesize nanotubes utilizes anisotropic materials as template. They are coated with silica using Si(OR)4 precursors and nanotubes of Si02 are obtained after removal of the template (Figure 1.24). 

Controlled drug delivery, membrane technology in, 15 847-848 Controlled drug release formulations (CDRFs), 9 51, 55 polymers in, 9 71-73 Controlled drug release systems, 9 50-51 design, 9 51-52 development, 9 55-57 intelligent, 9 56-57 in market, 9 83—85... 

Silicones are frequently used in transdermal drug delivery. Recently, the use of loosely cross-linked silicone elastomer blends for this application was surveyed.537 The mechanisms of controlled drug release in the silicone-based systems have been studied,538 as silicones are evaluated for relatively new protein drug-delivery systems.5... 

Controlled drug release A. Boddington, C. Grant, I. Omaswa, M. Patel... 

With continuous development of systems for controlled drug release, new materials are being used whose influence on peptide stability must be carefully examined. Thus, the model hexapeptide Val-Tyr-Pro-Asn-Gly-Ala (Fig. 6.30) embedded in poly (vinyl alcohol) and poly(vinyl pyrrolidone) matrices had rates of deamidation that increased with increasing water content or water activity, and, hence, with decreasing glass transition temperature (Tg). However, the degradation behavior in the two polymers differed so that chemical reactivity could not be predicted from water content, water activity, or T% alone. Furthermore, the hexapeptide was less stable in such hydrated polymeric matrices than in aqueous buffer or lyophilized polymer-free powders [132],... 

Most of the drug delivery systems that have been studied for clinical application are capable of rate- and/or time-controlled drug release. The therapeutic advantages in these approaches lie in the in vivo predictability of release rate, minimized peak plasma levels, predictable and extended duration of action and reduced inconvenience of frequent re-dosing and hence, improved patient compliance [1]. 

The fact that the luminal pH of the healthy distal colon is slightly higher than that of the proximal small intestine has led to the development of oral dosage forms that are intended to release the drug at the colonic pH (pH-controlled drug release). 

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