以多重乳化技術建構奈米脂質載體提升植化素之經皮吸收

Abstract

自然界有許多植物含有豐富的抗氧化物質，這些抗氧化物可有效降低自由基對細胞的傷害，進而阻止皮膚的老化，因此市面上許多護膚品都以植物萃取物作為重要配方成分。然而，不論是外用藥膏或是保養品，這些成分都需透過適當的載體包覆技術，才能穿透皮膚表面緻密的角質層，到達其發揮作用的位置。本實驗結合多重乳化技術與奈米結構脂質載體的概念，製作一粒徑大小介於 50 ~ 500 nm ，可同時搭載親脂性與親水性植化素的 W/O/W type 奈米脂質顆粒，藉由評估其載藥能力、 促經皮穿透率等特性，來優化該載體的組成，以期應用於提升各類活性物質對皮膚的保健功效。實驗初期以田口法及反應曲面法篩選製程中的重要變因，並取得相關變數的回歸方程式。結果發現，為尋求多重乳化液的穩定，須同時考量載體中的內水相W1比例與界面活性劑Span 80、Tween 80的添加量，進而得到粒徑小且物質包覆率高的載體；將上述優化的載體配方進行經皮吸收試驗，與控制組溶液相比後則得到促進比值。結果顯示，所製備的載體確實可以促進活性物質的經皮穿透，且其中以粒徑最小的配方 (102.2 ± 18.7 nm) 具最顯著的效果，推測原因為奈米大小的載體有利於在皮膚表層形成閉鎖效應，提高皮膚的保水量而寬廣化親水性通道，使得物質的經皮滲透性得以有效提升。為評估載體應用於經皮吸收系統的安全性及穩定性，分別以儲藏安定性試驗、細胞毒性測試及經皮穿透後的H&E染色切片來加以測定。使用人類真皮纖維母細胞進行細胞毒性測試，發現載體內含的親脂性界面活性劑Span 80，會與細胞膜的疏水區域作用而對細胞造成破壞。然而，皮膚切片的結果則顯示載體對整體皮膚結構並無明顯損害。另外，載體即使經歷反覆的冷凍解凍循環後，仍展現了良好的儲存安定性，未發生液滴聚集或活性物質大量損失的情況。因此推論，本次實驗所製備的W/O/W type奈米脂質載體，能夠以安全穩定又有效的形式應用於經皮給藥系統。

Various plant extracts exhibit strong antioxidant activities that can effectively reduce free radical damage, therefore could be used as anti-aging agent for topical cosmetics. However, it is well known that the stratum corneum, the outermost layer of the skin, constitutes an dense barrier to substances, pose a major difficulty for the transdermal delivery system. Therefore, it is necessary to construct an appropriate carrier to protect the internal active ingredients from deterioration and enhance its percutaneous absorption. The aim of this study was to combine the concepts of multiple emulsification technique and nanostructured lipid carriers to develop a W/O/W type nano-lipid particle system, which can encapsulate both lipophilic and hydrophilic phytochemicals with particle size distribution ranged from 50 to 500 nm. To optimize the composition of this carrier, we used Taguchi method and Response Surface Methodology as tools to get proper quadratic polynomial models, and used smaller size and higher encapsulation efficiency as desired functions. Results showed that the formulation with the lowest particle size had the highest enhancement ratio of permeation, most likely due to the occlusion effect of nano-size on skin hydration. Furthermore, cytotoxicity on skin fibroblast, histological appearance of skin and storage stability of carriers were evaluated. Results showed that the W/O/W type nano-lipid particle system posed limited risks to human skin. In addition, the system can remain stable after repeated Freeze-thaw cycles. In conclusion, the carrier system developed in this study is a safe and effective vehicle for transdermal delivery of phytochemicals.