I am preparing nanoparticle based drug nano carriers. I have seen in literature people discussing about 'long term stability' of nanocarrier. Long term stability' refer to how many hours or days ??? What are simple ways or technique by which we can study this.?
Z-potential and particle size measurements by dynamic light scattering.
long term (physical) stability usually means month, years.
Main processes of aging to consider in your case are agglomeration and Ostwald ripening. To be sensitive to appearance of first agglomerates separating methods for particle sizing, e.g. analytical centrifugation are of advantage.
Thanks for valuable suggestions. If I want to study long term stability , how can I do that, using which technique ?Which test?
As was suggested one can study change in particle size distribution, best with a separating method like analytical centrifugation. Could be also by a counting method, however, related methods are limited to larger size than nano.
Studying separation behaviour itself by analytical centrifugation or ultracentrifugation could also trace agglomeration or Ostwald ripening.
Whether for long term stability , I need to study chemical stability ( change in structure by xrd or ftir) also or studying physically stability ( size of particle) is enough.
of course both are basically important and the first will have an effect on the second. If you know there is high chemical stability obviously you can focus on physical stability.
I can say, Zeta Potential is an important and most advance tool for understanding the state of the nanoparticle surface and predicting the long term stability of the nanoparticle. Zeta Potential analysis is a technique for determining the surface charge of nanoparticles in solution (colloids). Nanoparticles have a surface charge that attracts a thin layer of ions of opposite charge to the nanoparticle surface. This double layer of ions travels with the nanoparticle as it diffuses throughout the solution. The electric potential at the boundary of the double layer is known as the Zeta potential of the particles and has values that typically range from +100 mV to -100 mV. The magnitude of the zeta potential is predictive of the colloidal stability. Nanoparticles with Zeta Potential values greater than +25 mV or less than -25 mV typically have high degrees of stability. Dispersions with a low zeta potential value will eventually aggregate due to Van Der Waal inter-particle attractions.
there is no long term thermodynamic stability of nanoparticles only kinetic stability. Electrostatic stabilization is only one option for stabilization against agglomeration, which is only one form of destabilization besides Ostwald ripening and coalescence. Besides at isoelectric point e.g. silica nanoparticles are highly stable against agglomeration.
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