Nanoparticle absorption enhancer

Calcitonin is another compound that was often incorporated into nanoparticles to enhance its oral absorption. Takeuchi et al. (2001) developed Elcato-nin-loaded PLGA nanospheres coated with chitosan, observing a reduction of blood calcium level. Sakuma et al. (2002) hypothesizes that both mucoadhesion of nanoparticles incorporating salmon calcitonin into the GI mucosa (Sakuma et al. 1999,2002) and increase in the stability of salmon calcitonin in the GI tract (Sakuma et al. 1997) result in the improvement of salmon calcitonin absorption. Moreover, chitosan-PEG nanocapsules increased the absorption of salmon calcitonin (Prego et al. 2006). 

Since the concentrations of insulin to be administered in the sheep model would have been large, the insulin-loaded chitosan nanoparticles were not investigated in that model. However, the pharmacodynamics and pharmacokinetics of various insulin-chitosan preparations were compared with postloaded insulin-chitosan nanoparticles. It was found that chitosan solution and chitosan powder formulations were far better, with the chitosan powder formulation showing a bioavailability of 17% as against 1.3 and 3.6% for the chitosan nanoparticles and chitosan solution [72], The effects of the concentration and osmolarity of chitosan and the presence of absorption enhancers in the chitosan solution on the permeation of insulin across the rabbit nasal mucosa in vitro and in vivo were investigated, and the same... 

Understanding the field enhancement of radiative rates is insufficient to predict how molecular photophysical properties such as enhancement of fluorescence quantum yield will be affected by interactions of the molecule with plasmons. A more detailed model of the photophysics that accounts for non-radiative rates is necessary to deduce effects on photoluminescence (PL) yields. Such a model must include decay pathways present in the absence of metal nanoparticles as well as additional pathtvays such as charge transfer quenching that are associated with the introduction of the metal particles. Schematically, we depict the simplest conceivable model in Figure 19. IB. Note that both the contributions of radiative rate enhancement and the excited state quenching by proximity to the metal surface will depend on distance of the chromophore from the metal assembly. In most circumstances, one expects the optimal distance of the chromophores from the surface to be dictated by the competition between quenching when it is too close and reduction of enhancement when it is too far. The amount of PL will be increased both due to absorption enhancement and emissive rate enhancement. Hence, it is possible to increase PL substantially even for molecules with 100 % fluorescence yield in the absence of metal nanoparticles. 

In another way, chitosan was used as a coating agent for nanoparticles to improve their bioadhesive properties after oral and nasal administration. Indeed, chitosan is known to have bioadhesive properties as well as an interesting absorption enhancing capacity. 

Alternative means that help overcome these nasal barriers are currently in development. Absorption enhancers such as phospholipids and surfactants are constantly used, but care must be taken in relation to their concentration. Drug delivery systems, including liposomes, cyclodextrins, and micro- and nanoparticles are being investigated to increase the bioavailability of drugs delivered intranasally [2]. 

Saretni, S., Atyabi, R, Akhlaghi, S. R, Ostad, S. N., and Dinarvand, R. (2011). Thiolated chitosan nanoparticles for enhancing oral absorption of docetaxel Preparation, in vitro and ex vivo evaluation of penetration enhancement properties, hit J. Nanomed., 6,119-128. 

Over the last decades, several academic and industrial research programs have been focused on the development and production of appropriate biocompatible formulations that provide enhanced therapeutic performance. Three different strategies can be discerned that are applied separately or in combination (i) addition of excipients to proteins, such as protease inhibitors, penetration or absorption enhancers like bile salts, fatty acids, cyclodextrins or surfactants " (ii) modification of the physicochemical properties of proteins, e.g. by attachment of lipophilic or hydrophilic moieties or (iii) incorporation of proteins into polymeric or liposomal delivery carriers. " A variety of polymeric vectors has been developed and exploited for this purpose, including biodegradable nanoparticles, nanogels, micelles, polymer bioconjugates and soluble nanocomposites. These polymeric carriers are more extensively described in the following sub-sections. 

Uptake via the nasal cavity to the brain, thereby bypassing the blood/brain barrier, can be improved using absorption enhancers and transporters such as chitosan nanoparticles.For example, Vaka and co-workers showed a 14-fold increase in rats in the bioavailability of intranasally administered NGF, a protein for the treatment of neurological diseases such as Alzheimer s, with chitosan compared to the formulation without chitosan. 

Sakuma, S., Suzuki, N., Kikuchi, H., Hiwatari, K. I., Arikawa, K., Kishida, A. and Akashi, M., Absorption enhancement of orally administered salmon calcitonin by polystyrene nanoparticles having poly(V-isopropylacrylamide) branches on their surfaces, Int. J. Pharm., 158, 69-78 (1997). 

Yakovlev and coworkers [402a, 402b] reported the IR absorption enhancement by mote than one order of magnitude for hydrocarbons adsorbed inside porous silicon, and assigned this effect to photon confinement in the microcavity acting like a multipass (Fabry-Perot type) cell. Recently, Jiang et al. [402c] observed a 50 times enhancement in the in situ IRRAS of CO adsorbed on Pd nanoparticles synthesized in cavities of Y-zeolite, as compared to the cases when the supports were ultrathin Pd films deposited directly on the zeolite or on amorphous alumosiUcate layer. 

Zhang X, Zhang H, Wu Z, Wang Z, Niu H, Li C. Nasal absorption enhancement of insulin using PEG-grafted chitosan nanoparticles. Eur J Pharm Biophatm. 2(X)8 68(3) 526-34. 

Different micelle formulations based upon the amphiphilic polymer poly(ethylenimine), PEI, loaded with cyclosporine A and formed into tablets were tested for comparative drug absorption against CsA-in-water and CsA-microemulsion in a rat model by Le and colleagues [34]. Various PEI-CsA nanoparticles were examined, which differed based on linear or branched formations of the polymer. They determined that polymer hydrophobicity was the primary determinant to enhance CsA encapsulation and oral CsA absorption (bioavailabihty), and not polymer molecular weight or polymer branching. Polymers need at least 10% of their monomers to exhibit hydrophobicity in order to encapsulate sufficient drug and enable oral absorption enhancement. In this study, only the most hydrophobic PEI-CsA nanoparticles produced significantly enhanced CsA absorption compared to CsA-in-water, but none were superior to CsA-ME. 

Finally, the new field of nanotechnology is now penetrating into biophotonies. Examples include the use of nanoparticles such as metal nanospheres or rods and quantum dots for enhanced cell and tissue imaging and local light energy absorption. The ehapter by C.E. Talley et al. discusses one specific implementation, namely the use of nanoparticles for enhancing Raman biospectroscopy. 

Optical absorption enhancement due to scattering from metallic nanoparticles... 

V. Kumar, H. Wang, Plasmonic Au nanoparticles for enhanced broadband light absorption in inverted organic photovoltaic devices by plasma assisted physical vapour deposition, Org. Electron. 14(2013)560-568. 

Wang X, Zheng C, Wu Z, Teng D, Zhang X, Wang Z, LiC. Chitosan-NAC nanoparticles as a vehicle for nasal absorption enhancement of insulin. J Biomed Mater Res B Appl Biomater. 2009 88(1) 150-61. 

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