Table 2.

Potential Spectroscopic PAT Sensors

Optical technique	Wavelength range	Attributes for PAT sensing	Companies implementing in-line sensors in their process	Refsa
UV-vis spectroscopy	240–340 nm	Cell density, aromatic amino acids	–	[48]
Circular dichroism	190–260 nm	Proteins secondary structure, aggregation.	–	[49]
FT-NIR spectroscopy	750–2500 nm	Chemical/biological compositions	Brucker, USA	[48]
Raman spectroscopy	100–3500 cm–1	antibody concentration	Pfizer, USA; GlaxoSmithKline, USA	[50]
Fluorescence spectroscopy	Excitation: 240–300 nm; emission: 260–450 nm	Cell metabolism, fluorescent compounds in media.	Sartorius Stedim Biotech GmbH, Germany	[28]
DLS	Visible light	Macromolecule diffusion	Colloid Metrix GmbH, Germany; Sanofi-Aventis Deutschland GmbH, Germany	[9]
SLS	Visible light	Size of macromolecules in solution	Sanofi-Aventis	[9]
Multiangle light scattering	Visible light	Protein aggregation	Merck & Co., Inc., USA; Wyatt Technology Corporation, USA	[51]

^aSee also [59., 60., 61., 62., 63., 64.].