Question

16. In designing nanomaterials for drug delivery application, size and shape of nanomaterials are important design factors. Provide your brief explanation as to why considering size and shape of nanomaterials will be critical for targeted drug delivery application. (5 pt)

Answer 1

Size :

Particle size plays a key role in particle functions, such as degradation, vascular dynamics, targeting, clearance and uptake mechanisms. Particles have been shown to have different velocities, diffusion characteristics and adhesion properties, depending on their size, resulting in different uptake efficiencies. The size of nanodrugs should be large enough to prevent rapid leakage in blood capillaries, but, at the same time, small enough to escape the capture of macrophages in the reticuloendothelial system, such as the liver and spleen.

Some outcomes

a. particles less than 200 nm in size will mainly follow endocytic pathways;

b. particles more than 200 Nm can be either engulfed through endocytosis or not internalized at all. Also they are filtered by liver, bone marrow and kidneys.

c. Particles less than 10 Nm are easily cleared by kidneys. Hence ideal size is between 10 - 200nm

Shape : The shapes of the nano particles play an important role in therapeutic delivery processes, such as particle adhesion, distribution and cell internalization. Most NPs have a spherical shape. With advanced nanofabrication techniques, different shapes and forms of NPs are developed with different geometrical, physical and chemical properties.

For example,

a. nanorods with suitable aspect ratios have been fabricated as a novel contrast agent for photothermal cancer therapy b. asymmetrically functionalized nanaoparticles have been assembled as nanochains

c. iron oxide-based nanoworms are developed for tumor targeting

d. nanonecklaces are assembled using gold NPs by covalent bonding