Metformin loaded silver nanoparticles were synthesized using ecofriendly method withextract of Azadiractha indica as reducing agent and two natural polymers; guar gum andxanthan gum, Sodium alginate, and a semi- synthetic polymer (AMS) as stabilizing agents.Twelve batches of nanoparticles were synthesized. Nanocomposites synthesized from AMSwere designated as AMS 1% NANOmet, AMS3% NANOmet and AMS5% NANOmet. Guargum stabilized nanoparticles were designated as GG1% NANOmet, GG3% NANOmet andGG5% NANOmet while Xanthan gum nanocomposites were coded as XG1% NANOmet,XG3% NANOmet and XG5% NANOmet respectively. Sodium alginate stabilizednanocomposites were designated as NaALG1% NANOmet, NaALG3% NANOmet andNaALG5% NANOmet respectively. The percentage yield of nanocomposites was high withvalues ranging from 80 % to 99.87 %. The entrapment efficiencies of the samples rangedfrom 63.06 % to 80.22 % while the loading capacities were in the range of 7.24 % to 24.10%. Differential scanning calorimetry showed there was no interaction between the polymersand metformin. Characterization of the metformin nanocomposites using UV- visspectroscopy, zeta sizer, scanning electron microscopy (SEM) and polydispersity wereperformed. The UV-vis spectroscopy showed surface plasmon resonance of 371nm for all thenanocomposites except XG5%NANOmet which had SPR of 335nm. The mean particle sizeof GG1%NANOmet was ideal with a value of 188.7nm followed by AMS1%NANOmet(386.7 nm). All the batches showed extended and sustained release profile with initial bursteffect at the first 30 min of release studies. Release of metformin in SIF was predominantlyhigher than in SGF. The kinetics of release was mainly zero order for all the nanocompositeswith the exception of NaALG5% NANOmet which released the drug by higuchi kinetics.Antimicrobial property of the optimized nanocomposites were similar (P>0.05). Generally,MIC values of the samples against the microorganisms tested ranged from 2500- 5000μg/ml.16In vivo anti hyperglycemic property of the optimized metformin nanocomposite usingglucose hyperload model results showed GG5%NANOmet as the optimum batch. At equaldoses it produced sustained and consistent significant (p<0.001) decrease in elevated bloodglucose level in glucose loaded hyperglycemic rats when compared with metformin and othernanocomposites treated groups.17CHAPTER ONE1.0. INTRODUCTIONIn recent years, there has been an exponential interest in the development of noveldrug delivery systems using nanoparticles . The transition from microparticles tonanoparticles has led to a number of changes in physical properties of materials . Two of themajor factors in this are the increase in the ratio of surface area to volume, and the size of theparticle moving into the realm quantum effects predominate. The increase in the surface-area-tovolumeratio, which is a gradual progression as the particle gets smaller, leads to an increasingdominance of the behaviour of atoms on the surface of the particle over that of those in theinterior of the particle. This affects both the properties of the particle in isolation and itsinteraction with other material. 
There have been tremendous developments in the field of Nanotechnology in recenttime with various technologies formulated to synthesize nanoparticles with specificcharacteristics on morphology and distribution . Although, there are several methods forthe synthesis of nanoparticles, they are very expensive and involve the use of toxic andhazardous chemicals which cause danger to humans and the environment . To overcomethese challenges, the eco-friendly synthesis of nanoparticles using environmentally benignmaterials like Plants , microorganisms [4,5], seaweed  and enzymes  were employed.It is a single step and offers several advantages such as time reducing, cost effective and Nontoxic.Nanocrystalline silver is a known Noble metal and they have tremendous applicationsin the field of Detection, Diagnostics, Therapeutics and Antimicrobial activity .In general, nanoparticles offer significant advantages over the conventional drug delivery interms of high stability, high specificity, high drug carrying capacity, ability for controlledrelease, possibility to use in different route of administration and the capability to deliverboth hydrophilic and hydrophobic drug molecules .