Table 2:
Methods to measure cell density
| Method | Measured Parameter | Advantages | Disadvantages | Ref. |
|---|---|---|---|---|
| Density Gradient Centrifugation | Buoyant density | Can be used to isolate cells, Easily accessible technology | Batch analysis, Suspended cells only | [10,40, 52] |
| Suspended microchannel resonator (SMR ) | Buoyant density | High accuracy, Single cell resolution | Suspended cells only | [15,16] |
| Particle tracking | Diffusion (large particles) | Spatial resolution, Takes particle size into account | Indirect density measurement, Sensitive to pH and specific interactions | [20,22–24,26] |
| Fluorescence correlation spectroscopy (FCS) | Diffusion (small particles) | Additional Information: concentration and complex stoichiometry | Indirect density measurement, Sensitive to pH and specific interactions | [27] |
| Fluorescence | Diffusion | Distinguishes | Indirect density | [28,29] |
| recovery after photobleaching (FRAP) | (small particles) | between mobile and immobile fraction | measurement, Sensitive to pH and specific interactions | |
| Refractive index tomography | Refractive index (proportional to density) | Spatial resolution, tag free, suitable for live imaging | [18,19] | |
| Cryo-electron tomography | Number and density of large structures | High spatial resolution | Fixed specimens only | [20,21] |
| Stimulated raman scattering microscopy (SRS) | Biomass composition and concentration | Distinguishes different classes of macromolecules, can be applied to tissues | Sensitive to autofluorescence | [35–37,39,123] |