Plant pollen is one of the most popular natural encapsulants. It can protect the genes and other enclosed biomolecules with its double-layered wall structure composed of cellulosic intine and sporopollenic exine and is produced in copious amounts, which makes it an ideal potential drug delivery platform with various health benefits. [13][14][15][16] We have previously used a protein-free microcapsule derivative known as a sporopollenin exine capsule from Helianthus [13] and Lycopodium [14] for molecular encapsulation purposes. The overall process simplicity and the advantage of high biocompatibility of natural microcapsules from pollens and spores makes them preferred drug carriers. However, ordinary natural encapsulants have demonstrated limited ability to accommodate single-component loads such as proteins and cells. [16]
Results and Discussion
Structural Characterization of Pine Pollen MicrocapsuleIn the present work, to overcome the problems associated with drug loading in conventional carriers, we developed a dual-molecular loading method utilizing natural pine pollen, which exhibits a bisaccate shape with a core-shell structure and is one of the most industrially active and consumed pollen species (Figure 1). [17] This structural uniqueness of pine pollen could impart it with a distinct loading-methoddependent spatial pattern. In this study, five molecular compounds with different sizes and electrical charges were chosen as a therapeutic and diagnostic model to explore their encapsulation behavior into natural pine pollen. The encapsulated molecules were fluorescein-isothiocyanate-labeled bovine serum albumin (FITC-BSA) and FITC-modified immunoglobulin G (IgG) as model therapeutic proteins; Doxorubicin HCl, an anticancer drug; and two organic dyes: Nile Red and Calcein. Simple loading methods namely: passive and vacuum-assisted loading were used with the mole cular loading being spatially and quantitatively ascertained. In addition, the structure of BSA molecules in the natural pine pollen was also investigated by circular dichroism (CD) to determine whether pollen can stabilize and protect encapsulated molecules and thereby function as future effective drug delivery systems.The loading of multiple drugs into a single carrier is an effective advanced clinical therapeutic for various diseases. Here, by exploiting the architectural features of natural pine pollen from Pinus massoniana, the spatially controlled encapsulation of two types of molecules in distinct compartments of a single microparticulate carrier is demonstrated. By simple vacuum and passive loading, diverse molecules such as proteins, organic dyes, and a drug are effectively encapsulated into the pollen microcapsule in binary fashion. This technique represents an advancement toward the use of natural pollen grains as a multifunctional molecular vehicle for functional drug delivery systems and innovative theranostic microdevices.
Dual Molecular Loading