Question 1

What are nanocarriers and why are they used for drug delivery?

Accepted Answer

Nanocarriers are submicron particles, typically less than 200 nanometers, loaded with therapeutic agents. Their small size enables access to many body sites and organs. Nanocarriers are usually biocompatible, meaning they don't harm living tissue or trigger immune responses. Their large surface area can be functionalized with ligands like antibodies to enable targeted delivery to specific cells.

Question 2

How does the EPR effect enable passive targeting of nanoparticles to tumors?

Accepted Answer

The enhanced permeability and retention effect, or EPR effect, occurs because tumor blood vessels form rapidly and are abnormal with large gaps in their endothelial lining. This leaky vasculature increases permeability, allowing nanoparticles to escape the bloodstream and accumulate within the tumor microenvironment without requiring specific targeting ligands.

Question 3

What is the difference between passive and active targeting with nanocarriers?

Accepted Answer

Passive targeting relies on the EPR effect, where nanoparticles naturally accumulate in tumors through leaky blood vessels. Active targeting uses functionalized nanocarrier surfaces with specific ligands that recognize and bind to receptors overexpressed by tumor cells, triggering receptor-mediated endocytosis for enhanced cellular uptake.

Question 4

How is scanning electron microscopy used to visualize nanoparticle biodistribution in tissue samples?

Accepted Answer

SEM uses backscatter electron detection to visualize metallic nanoparticles as high-contrast regions within tissue sections. Energy dispersive X-ray spectroscopy confirms nanoparticle composition by identifying characteristic X-rays emitted during electron beam interaction. This combination provides high-resolution imaging and increased confidence in detection compared to fluorescence methods.

Question 5

What tissue preparation steps are necessary before SEM imaging of nanoparticles?

Accepted Answer

Organs are fixed in phosphate-buffered formalin, then rinsed in PBS to remove excess fixative. Tissue is embedded in optimal cutting temperature compound and frozen at minus 80 degrees Celsius overnight. Cryostat sectioning produces 7-8 micrometer sections, which are collected on slides and treated with ethanol and acetone to remove OCT before SEM analysis.

Question 6

What does nanoparticle biodistribution data reveal about how the body processes metallic nanoparticles?

Accepted Answer

Biodistribution graphs show nanoparticle concentration in organs over time. An overall decrease after eight weeks indicates clearance from the body. However, increased liver concentration at four weeks suggests the body may process metallic nanoparticles as toxins. Nanoparticle size significantly affects cellular uptake rates and clearance kinetics.

Question 7

What are theranostics and how do they combine diagnostic and therapeutic functions?

Accepted Answer

Theranostics are loaded nanocarriers designed to simultaneously detect early-stage cancer and deliver chemotherapeutic agents. Metallic nanoparticles serve as contrast agents in imaging for tissue visualization, while also functioning as drug carriers. This integration of diagnostic imaging and therapeutic delivery enables both disease detection and treatment in a single platform.

Biodistribution of Nano-drug Carriers: Applications of SEM - Assessment Quiz