الفهرس 
Chapter 1: IntroductionOnly 14 pages are availabe for public view
 |  | from | 266 |  |  |
| | | from | 266 | | |
Abstract
Pollen and spores naturally protect the organism’s genetic material and other sensitive biomolecules and retain it in a viable state for reproduction, hence proving to be highly effective natural encapsulants. This motivates the need to explore them for encapsulation of functional bioactive molecules likes therapeutic drugs, organic and inorganic nanoparticles, and synthetic dyes etc. In this study, we have used drug delivery systems based on natural biopolymeric sporopollenin microcapsules derived from Lycopodium clavatum and to investigate their microencapsulation and release efficiencies. We have used different types of drug models to assess the encapsulation and release efficiencies of sporopollenin microcapsules. Also, different types of raw pollens were investigated for the encapsulation of other functional molecules. Moreover, more than one material can be encapsulated into pollens microcapsules via a chemical reaction inside their cavities. We believe that the significance of this study will be appreciated by a wide community of researchers working in the area of pharmaceutical applications, particularly those developing novel drug carriers. Furthermore, the uniformity, reproducibility, availability, resilience, and stability of such low-cost natural microparticles could make them competitive with other commercially available polymeric particles. These microcapsules have the capability to encapsulate and release actives in a controlled manner. The following main conclusions can be drawn with regard to the results obtained in each chapter of this thesis:
In Chapter (3), Folic acid (FA) is a crucial vitamin for all living creatures. However, it is susceptible to degradation under pH, heat, ultraviolet (UV) and day sunlight conditions, resulting in lowering its bioavailability. Therefore, a versatile protective encapsulation system for FA is highly required to overcome its inherent instability. We report the use of the robust Lycopodium clavatum sporopollenin (LCS) microcapsules, extracted from their natural micrometre-sized raw spores, for FA microencapsulation. The loading capacity (LC) and encapsulation efficiency (EE) of FA were 8.63% and 21.6%, respectively. The physico-chemical characterisation of the LCS microcapsules is comprehensively investigated before and after the microencapsulation using SEM, elemental, CLSM, FTIR, TGA/DTG and XRD analyses, revealing a successful FA encapsulation within the LCS in an amorphous form. The phenylpropanoid acids, responsible for the UV protection and the autofluorescence of the LCS, were found in the LCS as evidenced by FTIR analysis. TGA/DTG results revealed that the hemi-cellulose and cellulose are the major component of the LCS. A controlled and sustained release of FA from FA-loaded LCS were achieved where the release profile of FA-loaded LCS was found to be pH-dependent. The percentages of cumulative FA released after 10 h at 37 ± 0.5 °C were 45.5% and 76.1% in pH 1.2 and 7.4, respectively, ensuring controlled and slow release in simulated physiological conditions. The FA release kinetic studies indicated the prevalence of the Fickian diffusion mechanism in pH 1.2, while anomalous non-Fickian transport was ascribed for FA release in pH 7.4. The in vitro cytotoxicity assay revealed that the obtained formulations were biocompatible against the human skin fibroblast (HSF) cell line. The versatile LCS microcapsules exhibited intriguing photostability for FA under UV or sunlight irradiation. Concretely, the obtained FA sustained delivery and photoprotection properties of these LCS microcapsules validate their multifunctional characteristics, opening up intriguing applications in oral and topical drug delivery as well as in food industry.
In Chapter (4), ASA is a phenomenal drug that can be used in variety of conditions, has therapeutic usage as an analgesic to relieve pains and aches, an antipyretic, anticoagulant, platelet aggregation inhibitor, and as an anti-inflammatory drug. However, aspirin irritates the stomach lining, which may lead to stomach ulcers in high dosages. As a result, an appropriate dose must be used to minimise the adverse reaction of the gastrointestinal tract to aspirin. We have explored the feasibility of microencapsulation of ASA within sporopollenin microcapsules obtained from natural Lycopodium clavatum (LCS) spores to provide controlled and sustained delivery platform. The ASA loading capacity (LC) and entrapping efficiency (EE) were 26.7% and 53.4%, respectively. The physico-chemical characterisation of the LCS microcapsules is comprehensively investigated before and after the microencapsulation using SEM, FTIR, TGA/DTG and XRD analyses, revealing a successful ASA encapsulation within the LCS in an amorphous form. The absence of chemical interaction between the ASA and the biopolymer sporopollenin microcapsules is evidenced by FTIR analysis. A controlled and sustained release of ASA from ASA-loaded LCS were achieved where the release profile of ASA-loaded LCS was found to be pH-dependent. The percentages of cumulative ASA released after 10 h at 37 ± 1 °C were 51.7% and 66.9% in pH 1.2 and 7.4, respectively, ensuring controlled and slow release in simulated physiological conditions. The ASA release kinetic studies indicated the prevalence of the Fickian diffusion mechanism in all pHs used in this study. Our findings indicate that these resilient LCS microcapsules could be useful for ASA’s regulated and sustained delivery, creating a new generation of innovative oral and topical medication delivery capabilities. This controlled carrier could reduce the side effects of ASA, which are caused by its increased release into the GI tract.
In Chapter (5), we have demonstrated the successful microencapsulation of different biomolecules into natural thin-walled raw pollens from different species by simple different encapsulation methods. Also, we have used pollen microcapsules as chemical micro-reactors where a chemical reaction occurs inside the microcapsules to produce magnetite nanoparticles after sequential molecular loading inside. Our studies provide a clear proof that natural raw pollens are promising attractive microencapsulants employed for loading of various compounds. The demonstrated potential of natural pollens for encapsulation applications motivates further investigation as a delivery vehicle for various materials.