Controlled Release and Target Delivery of Nanoencapsulated Compounds

Based on the application of the encapsulated compounds, its release mechanism is tailored, such as a rapid-release system in local anesthetic lotions and slow release in sunscreens lotions. The release is generally controlled by the structure of the carrier matrices and Ficks’s diffusion, swelling, erosion, etc., mechanism. For example, if the compound is loaded in the outer shell of the nanocarrier, the release profile is rapid such as in the case of bioactive cyclosporine (Muller and Runge 1998). The release is slow if the compound is mixed in carrier matrice in solid-state (molecular dispersion). If the compound is entrapped within the core of the carrier matrix, the release is relatively slow. The matrix of the nanocarriers is controlled by its composition and physicochemical properties, such as solubility in different media. Once the nanosystem interacts with the changing environment, such as a change in pH value, temperature, ionic strength, etc., the structure tends to shift based on the above mentions mechanism. These mechanisms are broadly categorized into three different classes, including class I ideal fickian diffusion (Brownian transport), class II polymer relaxation-driven transport, class III anomalous behaviour (combination of class I and class II) (Bourbon et al. 2016a). During the preparation of nanostructures, if the concentration of the bioactive compound is soluble in liquid lipid but insoluble in a solid lipid, the compound will precipitate on cooling resulting in an active core coated with some dissolved compounds in lipid. But if the lipid solidifies rapidly, a bioactive shell will be formed. Generally, the prolonged-release is applicable for encapsulation of bioactive compounds as it tends to degrade in GIT due to the lipase-colipase complex. Therefore, the compounds’ release mechanism needs to be understood before fabricating nanostructures for its effective application in food formulations, pharmaceuticals, and nutraceuticals. Several experiments on the release mechanism of encapsulated compounds have been conducted in recent years (Bourbon et al. 2016b, 2003; Ramos et al. 2016). In one of the studies, the effect of GIT condition and release mechanism of curcumin and caffeine was evaluated in protein-based nano-hydrogels coated with chitosan. The results indicated enhanced stability and bioaccessibility of the bioactive compound in vitro GIT conditions (Bourbon et al. 2018). Stimuli-sensitive nanocarriers tend to modify their physicochemical properties and structure based on the internal or external stimulus actions. Presently, stimuli-based delivery of bioactive compounds with time and site-specific has gained popularity in the nutraceutical and pharmaceutical industries. Several modes of stimuli mechanisms have been developed, such as chemical (change in pH value), biological (wall matrices degradation enzyme), and physical (light, ultrasound, and temperature) for effective controlled target delivery of encapsulated bioactive compounds/drugs. Additionally, the stimulus release is extremely beneficial in the case of disease management, as when a unique stimulus compound is fabricated in nanocarriers, it specifically responds to the pathological trigger of that stimulus (Daglar et al. 2014).