Watal Geeta, Watal Aparna, Rai Prashant Kumar, Rai Devendra Kumar, Sharma Gaurav, Sharma Bechan
Medicinal Research Lab, Alternative Therapeutics Unit, Drug Discovery and Development Division, Department of Chemistry, University of Allahabad, Allahabad, India.
Methods Mol Biol. 2013;1028:147-51. doi: 10.1007/978-1-62703-475-3_9.
For centuries now, antioxidants have been known to provide better health by neutralizing the free radicals which are continuously produced in the human body. In normal circumstances, self-antioxidant defense system of the human body is capable of quantitatively managing the free radicals. However, in certain cases, which are at the threshold of developing diseases like diabetes and Alzheimer's, the human body calls for an external source of antioxidants. Since orally delivered antioxidants are easily destroyed by acids and enzymes present in the human system, only a small portion of what is consumed actually gets absorbed. Hence, there is a recognized and urgent need to develop effective methods for efficiently delivering antioxidants to the required sites. This chapter provides an in-depth overview and analysis of two such methods and processes-nano-encapsulation and nano-dendrimers. Among the various nanoscale delivery mechanisms, nano-encapsulation has emerged as a key and efficient delivery process. Designed as a spongelike polymer, nano-encapsulated antioxidants provide a protective vehicle which keeps antioxidants from being destroyed in the human gut and ensures their better absorption in the digestive tract. In fact, the nano-capsules bind themselves to the intestinal walls and pour antioxidants directly into the intestinal cells, which allow them to be absorbed directly into the blood stream. Another distinguished and popular mode for delivering antioxidants is that of nano-polymers known as dendrimers. Dendrimers involve multiple branches and sub-branches of atoms radiating out from a central core. Dendrimers afford a high level of control over their architectural design, including their size, shape, branching length or density, and surface functionality. Such flexibility makes these nanostructures ideal carriers in biomedical applications such as drug delivery, gene transfection, and imaging. Antioxidant dendrimers, made out of numerous units of antioxidants connected with each other in a branched fashion, provide numerous possible sites to couple with an active species and have enhanced free radicals scavenging potency. These dendrimer chains are biocompatible, biodegradable with nontoxic degradation products, and well suited for targeted drug delivery and other biomedical applications. Recent successes in simplifying and optimizing the synthesis of dendrimers, such as the "lego" and "click" approaches, provide a large variety of structures while at the same time reducing the cost of their production. The use of these highly branched, nanometer-sized, polymeric materials as nano-antioxidants for prevention and treatment of human diseases, associated with oxidative stress, is of immense public health relevance globally.
几个世纪以来，人们一直都知道抗氧化剂通过中和人体中不断产生的自由基来改善健康状况。在正常情况下，人体自身的抗氧化防御系统能够定量控制自由基。然而，在某些情况下，比如处于糖尿病和阿尔茨海默病等疾病发展的临界状态时，人体就需要外部的抗氧化剂来源。由于口服的抗氧化剂很容易被人体系统中的酸和酶破坏，实际摄入的只有一小部分能被吸收。因此，迫切需要开发有效的方法来将抗氧化剂高效地输送到所需部位。本章深入概述和分析了两种这样的方法和过程——纳米封装和纳米树枝状大分子。在各种纳米级递送机制中，纳米封装已成为一种关键且高效的递送过程。纳米封装的抗氧化剂被设计成海绵状聚合物，提供了一种保护载体，可防止抗氧化剂在人体肠道中被破坏，并确保它们在消化道中更好地被吸收。事实上，纳米胶囊会附着在肠壁上，将抗氧化剂直接注入肠细胞，从而使其能够直接被吸收进入血液。另一种卓越且流行的抗氧化剂递送方式是被称为树枝状大分子的纳米聚合物。树枝状大分子包含从中心核向外辐射的多个原子分支和子分支。树枝状大分子在其结构设计方面具有高度的可控性，包括其大小、形状、分支长度或密度以及表面功能。这种灵活性使这些纳米结构成为生物医学应用（如药物递送、基因转染和成像）中的理想载体。由众多以分支方式相互连接的抗氧化剂单元制成的抗氧化树枝状大分子，提供了众多与活性物质结合的可能位点，并具有增强的自由基清除能力。这些树枝状大分子链具有生物相容性，可生物降解且降解产物无毒，非常适合靶向药物递送和其他生物医学应用。最近在简化和优化树枝状大分子合成方面取得的成功，如“乐高”和“点击”方法，在降低生产成本的同时提供了多种多样的结构。将这些高度分支的纳米级聚合材料用作纳米抗氧化剂来预防和治疗与氧化应激相关的人类疾病，在全球范围内具有重大的公共卫生意义。
