Encapsulation of living cells into sporopollenin microcapsules

Abstract

We demonstrate that living cells can be encapsulated inside sporopollenin microcapsules derived from Lycopodium clavatum. To encapsulate large objects like cells, the sporopollenin particles are compressed into a pellet which forces their trilite scars to open up. Our method involves exposing a sporopollenin pellet to an aqueous suspension of cells in the presence of a surface active agent which facilitates the capillary suction of the cells suspension inside the compressed sporopollenin and its ''re-inflating'' and closure of trilite scars. We demonstrate that the viability of the cells is preserved after the encapsulation in the sporopollenin capsules which contain a significant amount of entrapped cells and show biological activity when placed into a culture medium. Since the sporopollenin nanopores allow nutrient transport across the capsule wall, it could be used for controlling the rate of in situ fermentation reactions or as bio-reactors. We also show that sporopollenin can be loaded with magnetic nanoparticles and live cultures simultaneously which would allow remote manipulation, fixation, removal or potentially targeted delivery of such bio-microreactors. The encapsulation of living cells inside sporopollenin can be used for many different purposes in the food and pharmaceutical industries, including protection of probiotics in foods and delivery of live vaccines for pharmaceutical applications.

Fabrication and Characterisation of Novel Natural <i>Lycopodium clavatum</i> Sporopollenin Microcapsules Loaded <i>In-Situ</i> with Nano-Magnetic Humic Acid-Metal Complexes

“…It is worth stress that loading these empty SP microparticles with the desired materials can be achieved either by passive diffusion of active materials through the nano-channels present on their surface and/or through the opening of the Y-shaped trilete scars (Figure 1(c)) via compressing the SP powder as a tablets (disk) before introducing to the solution in the correct step of loading to allow more materials to be entrapped inside the empty core ensuring an efficient encapsulation. That latter compressed tablet protocol was recently introduced by Paunov et al [12] for encapsulating of large living cells into SP.…”

“…We extracted sporopollenin from Lycopodium clavatum pollen by suspending 100 g raw dry pollen powder in 800 mL acetone and stirred under reflux for 5 hours [12]. The de-fatted pollens were then filtered and 800 mL of 6 wt% KOH solution was added under reflux for 12 hours while the suspension was filtered and replaced once in the middle of the process.…”

“…These different materials were loaded into the empty sporopollenin via either surface physical adsorption and/or the passive diffusion through the nano-channels (40 nm in diameter), existing on the SP surface, into the inside core of SP [11]. Paunov et al [12] [13] demonstrated a new protocol for the encapsulation of living large cells such as yeast cells and different organic or inorganic materials into the exine of pollens from Lycopodium clavatum plants.…”

Sporopollenin microcapsules for microencapsulation of living cells

“…Mackenzie et al Paunov et al [9] developed a simple and robust method for loading sporopollenin exine of Lycopodium Clavatum with inorganic and organic nanoparticles synthesized in situ by using sporopollenin microcapsules as chemical micro-reactors with chemical reaction (or precipitation process) generating a large amount of a product of low solubility inside the microcapsule shells. Recently, Hamad et al [10] extended this technique to allow effective encapsulation of bigger particles, like cells, into sporopollenin microcapsules. This allowed alternative techniques for protection of cells to be developed.…”

Sporopollenin, The Least Known Yet Toughest Natural Biopolymer

“…Normally, encapsulation into the exine's available chamber is via the nano-diameter channels that penetrate them. However, it would appear that compression of the dry exines under some 5-10 tonnes/cm 2 can open the trilete scar feature of the exines, allowing entry of living yeast cells into the exines' chambers Hamad et al, 2011). After this process, the cells still remain viable within the chamber and the exines undamaged, which further illustrate the remarkable elasticity and physical robustness of the exines.…”