Nanotechnological approaches to enhance the bioavailability and therapeutic efficacy of green tea polyphenols

Oral delivery is the most common method for drug administration. However, poor solubility, stability, and bioavailability of many drugs make achieving therapeutic levels via the gastrointestinal (GI) tract challenging. Drug delivery must overcome numerous hurdles, including the acidic gastric environment and the continuous secretion of mucus that protects the GI tract. Nanoparticle drug carriers that can shield drugs from degradation and deliver them to intended sites within the GI tract may enable more efficient and sustained drug delivery. However, the rapid secretion and shedding of GI tract mucus can significantly limit the effectiveness of nanoparticle drug delivery systems. Many types of nanoparticles are efficiently trapped in and rapidly removed by mucus, making controlled release in the GI tract difficult. This review addresses the protective barrier properties of mucus secretions, how mucus affects the fate of orally administered nanoparticles, and recent developments in nanoparticles engineered to penetrate the mucus barrier. Copyright © 2011 Elsevier B.V. All rights reserved.

At the beginning of the nineties solid lipid nanoparticles (SLN) have been introduced as a novel nanoparticulate delivery system produced from solid lipids. Potential problems associated with SLN such as limited drug loading capacity, adjustment of drug release profile and potential drug expulsion during storage are avoided or minimised by the new generation, the nanostructured lipid carriers (NLC). NLC are produced by mixing solid lipids with spatially incompatible lipids leading to special structures of the lipid matrix, i.e. three types of NLC: (I) the imperfect structured type, (II) the structureless type and (III) the multiple type. A special preparation process-applicable to NLC but also SLN-allows the production of highly concentrated particle dispersions (>30-95%). Potential applications as drug delivery system are described.

Green tea polyphenols have been extensively studied as cardiovascular disease and cancer chemopreventive agents in vitro and in animal studies. However, the effects of green tea consumption in humans remain unclear. To investigate the associations between green tea consumption and all-cause and cause-specific mortality. The Ohsaki National Health Insurance Cohort Study, a population-based, prospective cohort study initiated in 1994 among 40,530 Japanese adults aged 40 to 79 years without history of stroke, coronary heart disease, or cancer at baseline. Participants were followed up for up to 11 years (1995-2005) for all-cause mortality and for up to 7 years (1995-2001) for cause-specific mortality. Mortality due to cardiovascular disease, cancer, and all causes. Over 11 years of follow-up (follow-up rate, 86.1%), 4209 participants died, and over 7 years of follow-up (follow-up rate, 89.6%), 892 participants died of cardiovascular disease and 1134 participants died of cancer. Green tea consumption was inversely associated with mortality due to all causes and due to cardiovascular disease. The inverse association with all-cause mortality was stronger in women (P = .03 for interaction with sex). In men, the multivariate hazard ratios of mortality due to all causes associated with different green tea consumption frequencies were 1.00 (reference) for less than 1 cup/d, 0.93 (95% confidence interval [CI], 0.83-1.05) for 1 to 2 cups/d, 0.95 (95% CI, 0.85-1.06) for 3 to 4 cups/d, and 0.88 (95% CI, 0.79-0.98) for 5 or more cups/d, respectively (P = .03 for trend). The corresponding data for women were 1.00, 0.98 (95% CI, 0.84-1.15), 0.82 (95% CI, 0.70-0.95), and 0.77 (95% CI, 0.67-0.89), respectively (P<.001 for trend). The inverse association with cardiovascular disease mortality was stronger than that with all-cause mortality. This inverse association was also stronger in women (P = .08 for interaction with sex). In women, the multivariate hazard ratios of cardiovascular disease mortality across increasing green tea consumption categories were 1.00, 0.84 (95% CI, 0.63-1.12), 0.69 (95% CI, 0.52-0.93), and 0.69 (95% CI, 0.53-0.90), respectively (P = .004 for trend). Among the types of cardiovascular disease mortality, the strongest inverse association was observed for stroke mortality. In contrast, the hazard ratios of cancer mortality were not significantly different from 1.00 in all green tea categories compared with the lowest-consumption category. Green tea consumption is associated with reduced mortality due to all causes and due to cardiovascular disease but not with reduced mortality due to cancer.