Pectin-Zein Hydrogel for delivery of Drug and Nutrient.

ZK Muhidinov1, GF Kasimova1, AS Nasridinov1 KH.Teshaev1and LS Liu2

1Chemistry Institute of Tajikistan Academy of Sciences, Dushanbe 734063, Tajikistan
2Easter Regional Research Center ARS USDA, 600 East Mermaind line, Wyndmoor, PA 19038, USA

One of the current objectives in the development of microencapsulated drug and diet for medical application is to increase delivery of water-soluble drug and nutrients High inclusion (IE), encapsulation (EE), delivery (DE) and retention efficiencies (RE) are necessary to compensate for high leaching losses1. However, most encapsulation methods developed for delivering drug& nutrients to organisms result in inherently low IE, EE, DE and RE due to preparation methods and physical characteristics of particles2. 
This study aimed to develop a hydrogel microparticle from hydrophilic and hydrophobic biopolymers of corn zein and different pectin that effectively entraps and retained colon specific drugs and nutrients. Differential turbidimetric titrations curves in combination with potentiometric and conductometric curves were explored to evaluate corn zein molecular fractions and its complex formation with different pectic polysaccharides. Isolated corn  zein fractions profile corresponding to the literature data related to the two polypeptides of α-zein; γ-zein; β-Zein  and δ -zein, respectively were used as hydrophobic polymers. Pectic polysaccharides having different molar mass and degry of esterificatiuon were applied as a hydrophilic polymers. Here turbidimetric titration method for investigation of ionotropic geletion process between corn zein and different pectins in water-ethanol solution in presence of Ca++ and Zn++ ions was studied. From differential curves the solution turbidity (complex formation) increase with increasing of zein concentration in solution from 0.05 to 0.5%. The maximum peaks values increase also with increasing of croslinking ion consentration from 0.0028 to 0.028%, but moves to higher zein/pectin ratio. Bimodal distribution of the curves, probably, related with the formation of two type of complexs: one through of elctrostaic interaction by pectin-Me++-zein and the second via hydrophobic interaction of pectin-zein macromolecules. 
To evaluate the drug transport mechanism, thus optimized zein/pectin gelation process were applied to tailore a delivery system for encapsulation of model drug, than drug relaese was tested by in vitro, ex vivo and in vivo experiments through mathematical models. The results shows that hydrogel prepared with different pectin/zein ratio exhibited a lower drug diffusion coefficient. Values of De and Dl for the hydrogels prepared with LM citrus pectin slightly increase with  increasing zein fraction, whereas in case of apple pectin hydrogels the value of De significantly increase from 13.92x10-9 cm2s-1 to the 460.4 x10-9 cm2s-1. This indicate that the drug diffusion manly controlled by zein fraction and its interaction with pectin in the hydrogel. Obtained data represent the certain interest, as for preparation of complexes stable to the degradation at the upper gastrointestinal site, which retard drug release and protect protein fraction from the pepsin attacks. Pectin fraction in complex stabilized by metal cross linking network protects protein from protease attacks. While zein fraction, in turn, suppressed pectin polyelectrolyte swelling degree favoring drug release.
The relevant relationship existing between the microspheres composition and drug release behavior can be exploited to develop unique drug&nutrient delivery devices with exclusive defined release properties.  

References:
1.	Önal, U., Langdon, C.J., (2005). Performance of zein-based particles for delivery of riboflavin to early fish larvae. Aquac. Nutr. 11, 351–358.
2.	Liu LS.,Kost J.,Fishman M.L.,Hicks K. A (2008). Review: Controled Release Systems for Agricultural and Food Applications, in New Delivery Systems for Controled Drug Release from Naturally Ocuring Materials. Ed. N.Parris, LS Liu et al. ACS Symposyum series 992, 265-281.