Himanshu Antil

Plga has a non-ionic water-soluble polymer structure. In water, like surfactants, Plga form micelles. The formation of micelles is accompanied by a liquid-liquid (water-water) phase transition in an ensemble of small water systems. This occurs in the femtosecond range and is recorded by the DLS as water fluctuations. When you remove Plga, only water fluctuations remain.

Doctors of homeopathy treat with such fluctuations of water after medicines. However, as in your case, fluctuations of water ("polymer traces") remain. After a while, they should disappear. Check it out. Read about the water-water phase transition in our article

Article Liquid Polyamorphous Transition and Self-Organization in Aqu...

Himanshu Antil

I assume you're filtering all your liquids to better than 0.02 μm? All the signs you give point to large contamination of your system which is improved after centrifugation. For small systems I'd be looking at quartz (rather than plastic) cuvettes as the optical quality is far superior.

It can certainly happen that lyophilization can lead to aggregation, see for example

Article Protein aggregation and lyophilization: Protein structural d...

@Ulf nobbmann what can i do to avoid the protein aggregation in the lypholization step.

Himanshu Antil to avoid nanoparticle aggregation during lyophilization, use a stabiliser eg. tween 80 or a cryoprotectant. I am using cryoprotectant, Trehalose (2.5% w/v) in water to wash my pellets before lyophilization. They stabilise the nanoparticle and prevents agglomeration.

@abhinaya shanmugavadivu...thankyou i will follow the same .. actually I was using mannitol as a cryoprotectant before lypholization still it was showing aggregation..