Hi
I am trying to Synthesis gelatin (type A) nano particles by two-step desolvation method. By DLS, the dimension of gelatin particles are less than 50 nm. I am not sure what is wrong with my work.
I solved 1.25 g gelatin in 25 ml DI water at 50 OC under stirring (600 rpm) for 40 min. Then I added 25 ml acetone and left it for 1 hour at room Temp. A thin layer of gelatin was formed on the bottom of the beaker. I removed the top solution and solved the precipitated gelatin to 25 ml DI water at 50 oC for 40 min, again. Then I adjusted the pH on 3.5 by HCl. After that, 75 ml acetone added to the sample drop-wise (by syringe pump, 4 ml/min, stirrer: 1000 rpm). Then 126 um Glutaraldehyde (50 wt.%) was added to the sample under stirring for 16 h. In this step I checked the particle size by DLS. The size-number graphs showed that the size of the particles is about 20 nm. The poly dispersity is 0.57.
I do not know what is the problem.
In advance, thank you for your help.
Dear Gelareh,
I would never use Number-based DLS data, but rather Intensity-based data. Number-based is derived mathematically from intensity data and involves conversion of the size distribution over D6 . So, any random noise is blown up out of proportion. If also in intensity-based data you see 20 nm 'particles' with a PDI of 0.57 it seems to suggest that you have only dissolved and partly aggregated macromolecules. Something in your cross-linking (this is what the glutaraldehyde is for, right?) may have gone wrong.
Next, I note that you use pH= 3.5. If your procedure aims at neutralizing the gelatin this is the right pH, but if you need gelatin to be charged this pH is below its pKa (which is about 4).
I would review the procedure you use iwth the original method given by Marty and coworkers: Marty JJ, Oppenheim RC, Speiser P.,Nanoparticles - a new colloidal drug delivery system. Pharm Acta. Helv. 53(1): 17-23, 1978
I hope this helps, kind regards, Leo
gelatin can be considered as a culture medium, a possible contamination can be the source of the problem. It is advisable to work in septic conditions.
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