Table 1.

Comparison between conventional in vitro (2D and 3D), ex vivo, in vivo models and microfluidics systems.

Characteristics	2D culture	3D culture	in vivo	ex vivo	Microfluidics
Ease of assay	Easy to perform	Difficult to form uniform 3D models	Requires specialization. It is also laborious and time-consuming	Requires optimization. It is time consuming	Requires specialized equipment for chip fabrication and trained personnel
Time required	Low	Moderate	Very high	Very high	Moderate
Reproducibility	High	Moderate	Low	Low	High
Cost	Low	Moderate	Very expensive	Expensiv	Moderate (The assays are cheap but expensive equipment is needed)
High throughput screening	Possible	Possible	Not possible	Not easy	Possible
Main applications	Invasion, proliferation, cell-signaling, drug response studies	Invasion, cell-cell/matrix interactions, intra and extravasation, hypoxia, drug response	Metastasis, drug response, mutation studies	Anticancerous drug testing and biomarkers discovery	Multicellular interactions and recapitulation of in vivo conditions such as vasculature, fluid flow, biochemical gradient is possible; can incorporate immune cells; provides an ethically relevant substitution of in vivo model
Sample volume requirement	Low	Low	High	High	Very low
Biological relevance	Limited relevance (cell display artificial phenotypes and perturbed gene expressions)	Higher biological relevance (compared to 2D)	Very high biological relevance (compared to 2-D and 3-D); Provides physiological microenvironment and vasculature;	Higher biological relevance	Very high biological relevance
Main limitations	Lack of vasculature and cell-matrix interactions Lack of perfusion	Lack of vascularization. Lack of perfusion	Mostly suffer to demonstrate immunomodulatory effect. Non-predictive	Lack of vasculature and perfusion. Short observation period.	Difficult to collect cells for analysis