If you lyophilize without any cryoprotectant aggregation is bound to occur and the aggregates will take longer time to get dispersed in water. So add 5% mannitol to aqueous dispersion of nanoparticle and lyophilize.You will get the desired particles.

Please refer our paper entitled "Diclofenac-loaded Eudragit S100 nanosuspension for ophthalmic delivery , Journal of microencapsulation. 01/2011; 28(1):37-45."

We have discussed the same.

Please make a more specific question saying what is the nanoparticles composition, what is the solvent, what is the particle size, if the nanoparticle are functionalized, etc...

Solvent is cholroform, its not functionalized and particle is around 120nm and the polymer is pla

If you are talking about polymeric nanoparticles, then it could have been aggregated, rendering the particles non dispersible.

Then wat can be done ... They are pretty much stable before lyophilizing it ..

Do you lyophilized or Vacuum dried.............if you use cholroform surely you can redissolve it in the same along with polar buffer.

To: thomas .. I dont want to dedissolve it... I just want to re disperse it in water.

You can sonicate your samples for say 30 min and then examine there zeta potential that will give you some idea whether they agglomerated or not..!!!! I hope this will work or else try preparing NPs with some capping agent or stabilizer e.g. starch or some organic acid..

Thank u..

What is your cryoprotectant? If glucose the problem was it... maybe if you test the trehalose... which is the manner of you freeze your samples? I don't recommend the sonication because sonication itself is a high energy disgregating, and thus you could have an "apparent" and unstable size of particle...

to rivera : i dont use any cyroprotectant as of now. will that help in redispersing my the NPs? i dont much insight about using glucose or trehalose ... just help me na...

Lyophylization would not cause any change in the particle characteristics. The material should have the same properties as before. If it was soluble in water previously, it should be soluble in water after lyophylization too ! Now, since chloroform is a highly polar solvent and water is not as polar as chloroform, the solubility might be less in water when compared to chloroform. But, some of it would still go in the solution. What exactly is the polymer? We had similar issues with HPMA !

hi gaurav ..

i am using PLLA. i used cholroform dissolving the polymer . NPs are formed in water only using nanoemulsification technique. it wat pretty stable in water for a week ... after lyophilzation its not redispersing ..

Use acetone instead of chloroform, for example. Increase the proportion of water versus solvent, during the emulsion process. Also important is the molecular weight of PLLA. Suitable lower molecular weight.

Salt is too high. Salts screen the charge of ligands on particles, allowing aggregation and can reduce solubility in polar environments. Try washing 3x with fresh 70% ethanol by letting it roll gently across the surface of the pellet and then pulling off. Or mix well and centrifuge for ~20 mins.

Maybe a sonication can help resuspend. Usually works with nanoparticules covered with citric acid. But be careful with the frequency and intensity.

hi Dr Nenad .

i found PLLA donot dissolve in acetone in 25 degree celcius. i think i need to heat atleast to 40 degree celcius to dissolve. problem is the drug which i ll using is heat sensitive . so i thought this wouldnt be proper to use. i hope this will correct. your suggestions are welcomed .

After determining the zeta potential you can use the appropriate surfactant (anionic or cationic) to improve redispersion. Normally using the correct surfactant with sonication process it is possible to obtain a high redispersion degree. It is important to study the appropriate amount of surfactant to prevent new reagglomeration through the depletions phenomena, for example.

Find attached our paper describing several excipients for protectinhg nanoparticels against freezing and dehydration stress

thank u Dr.Wagner for sharing your paper.

You may consider contact with who works at HCTM, Kaithal, India and is actively engaged in preparing new nanomaterials in his lab. there

Narendra Nath

Try to follow the manufacturer's recommendation regarding the solvent to use.

When you lyophilize your nanomaterials (NMs) you need to find the most suitable stabilizing agent. You also need to find the most suitable ratio between the stabilizer and the nanomaterials. At the happy medium, the NMs will redisperse very easily; otherwise they aggregate.

If you lyophilize without any cryoprotectant aggregation is bound to occur and the aggregates will take longer time to get dispersed in water. So add 5% mannitol to aqueous dispersion of nanoparticle and lyophilize.You will get the desired particles.

Please refer our paper entitled "Diclofenac-loaded Eudragit S100 nanosuspension for ophthalmic delivery , Journal of microencapsulation. 01/2011; 28(1):37-45."

We have discussed the same.

A useful method was adding some water-soluble polymer(oligomer), such as PEG and Dextran, into the solution before lyophilizating the nanoparticle. Owing to the strong inter-particle interaction, the lyophilized nanoparticles are hard to re-disperse. The water soluble polymer could reduce the interaction; if needed, it could be removed by dialysis with ease.

You can also try mannitol, glucose, and other sugars as stabilizers during lyophilization of nanomaterials.

Powders of nano particles have tend to have agglomerates. Because of the little diameters these agglomerates are harder to disperse than agglomarates of the same material with micro-sized particles. So you won't get along just with stirring or rotor-stator mills. But a bead mill will do a good job, filled with 0,8mm -1mm CeO-beads.

A disersing agent might be used to stabilize the particles and to prevent reagglomeration. But this will influence the of the final product, filled with your nano-particles.

In which solvent you want to suspend them. Chances are there that they are gettin g aggregated. you can use sucrose as cryoprotectant during lyophilisation

Hello,

first optimize the suitable cryoprotectant concetration using various concentrations of cryoprotectating agents like : 1%,2%, 5% of sucrose, mannitol, dextrose, lactose, trehalose. If cryoprotectnat concentration is not sufficient to stabilize the nanopartilces, they may aggregate and unable to re suspend in water, so you have to optimize the suitable concentration of cryoprotectant or optimize the freeze drying cycle. Please not that sf/si valUE should be near to 1.

Hi dalapathi... thank u... whatz mean by sf/si ?? how does disaccharides help in re-suspending NPs???

Hi Sf/si vale is : particle size of after freeze drying/particle size of before freeze drying;and while selection of cryoprotectants we need to select water soluble agents mostly prepare disacharides...