I think the barrier is in two issues. First in the composition of the nanoparticles. These are generally metallic (gold or silver) and must overcome the pharmacokinetic and pharmacodynamic limitations that allow their authorization. The second key is "vectorization". That is, how to selectively direct them to the appropriate and specific "stable" target. I believe that in this sense the use of combined technologies (for example: nanoparticles with a specific pharmacological load, selective and activated by radiotherapy).

Dear @ Dr Eduardo García-Rico

Thanks for your insight in to a difficult situation. You are very right in explaining the barriers. What about liposomes as carrier? And what about any breakthrough in near future?

Hello Lileswar Kaman

Though Nanotechnology has advanced it will still take a while to reach the clinics for the following reasons:

1. The in-vitro and in-vivo physiochemical properties of nanoparticles still need to be understood fully. It is difficult to predict how they will penetrate organs or get metabolized. This makes biodistribution and toxicity studies more challenging.

2. Nanomaterials are not uniform in their toxic effects.

3. The in-vivo analysis of nanoparticles is yet in the stage of infancy. Tracking nanoparticles is difficult. In some cases they may stay for a long period without breakdown while in others the nanoparticles may bind to proteins and fail to show its effect on the target.

4. The ADME ( Absorption, Distribution, Metabolism and Excretion) for nanoparticles differ from those for other molecules. This could also pose a barrier in the development of nanomedicine.

5. Not much work has been carried out on surface interactions which could give an idea of the physical and chemical properties of nanomaterial that could put some light on the interaction of nanoparticles within the cells.

6.There are also issues concerning occupational safety for the researchers in the laboratory and the workers in the production unit as far as nanomaterial is concerned.

Thank you.

liposomes are already used, generally with more micrometric than nanometric sizes. For example with Doxorubicin or Trastuzumab, even to encapsulate mRNA in anti-SARS vaccines. However, in these the specificity depends more on the drug than on the vector. Alternative options with a future are polymersomes, dendrimers or other polymers that may have specificity.This specificity may depend on monoclonal antibodies or nucleotide sequences, for example.

Dear @ Dr Malcolm Nobre

Thanks for your answer. All six points you have mentioned are very valid and pertinent. These barriers are complex and may be working in combinations and making it more difficult for clinical applications. But how to overcome them is the challenge. The initial euphoria and enthusiasm is a bit waning. But basic and translational scientists should keep on trying. Potential is there.

Dear @ Dr Eduardo García-Rico Thanks for your answer. You are very right about the Polymersomes, dendrimers and other polymers and regarding monoclonal antibodies in drug delivery system. But still routine clinical applications is not there.

We can see the future but we are not there yet!

I think its important to keep in mind the properties of the tumor and incorporate direct targeting strategies to tumors. I think that biotechnological advances are paving the way for better clinical outcomes. Drug delivery systems need to be designed to mimic the in vivo environment and computer aided simulations are a growing resource for it.

Dear @ Dr Nabeela Sayed I will agree with you views regarding the need to keep in mind the tumor properties during development of drug delivery system. Regarding computer simulated environment for further development is a promising one.

Still the complexity of barrier in clinical application will remain.