NO-releasing nanoparticles

Synthesis and characterization of a new NO-releasing scaffold prepared from amine-functionalized silica nanoparticles... 

NO-releasing biomaterials have been developed for antibacterial applications including polymeric materials, xerogel, sol gel,i i and silica nanoparticles. Two different classes of NO donors, diazeniumdiolates and nitrosothiols, are commonly used. The diazeniumdiolates, also called as NONOates, are synthesized by reaction of amines with NO gas to form relatively stable compounds that spontaneously release NO on contact with bodily fluids. 

As of today, there are no commercially available pharmaceutical products of this technology. The pharmaceutical industry however, is involved in developing nanoparticle-based delivery systems. Use of nanospheres to modify the blood-brain barrier (BBB)—limiting characteristics of the drug enables targeted brain delivery via BBB transporters and provides a sustained release in brain tissue and vaccine delivery systems to deliver therapeutic protein antigens into the potent immune cells are under investigation.103... 

Figure 4. Effect of Ti02 and Si02 nanoparticles on the release of betamethasone from liposomes (O) no particles and in the presence of (A) Ti02 and ( ) Si02 particles.

In vivo antigen release from nanoparticles (at SQ and OR immunizations) was designed to take place for several days to weeks. However, rigorous experiments to show that no booster immunization is necessary have not been conducted. The most significant finding of the immunization study was the fact that only nanoparticulate PDA-cross-linked antigen was active in oral applications, in spite of relatively low PDA/OVA ratio used (0.021). 

In order to achieve a sustained drug release and a prolonged therapeutic activity, nanoparticles must be retained in the cul-de-sac and the entrapped drug must be released from the particles at a certain rate. If the release is too fast, there is no sustained release effect. If it is too slow, the concentration of the drug in the tears might be too low to achieve penetration into the ocular tissues [208]. The major limiting issues for the development of nanoparticles include the control of particle size and drug release rate as well as the formulation stability. 

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