Table 2.
List of analytical tools useful for providing different types of information directly on aluminum-adsorbed antigen(s) without any desorption needed. Full names of techniques listed in the table: attenuated total reflectance Fourier transform infrared (ATR-FTIR), near-infrared (NIR), circular dichroism (CD), intrinsic fluorescence (IF), extrinsic fluorescence (EF), differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR), confocal microscopy and high content fluorescence imaging analysis (Imaging), flow cytometry (FC), enzyme-linked immunosorbent assay (ELISA), direct Alhydrogel formulation immunoassay (DAFIA), Raman spectroscopy (Raman), and liquid chromatography–mass spectrometry (LC–MS).
| Analytical Tool | Type of Information | Application | Type of Vaccine | References |
|---|---|---|---|---|
| ATR-FTIR | Secondary protein structure: focus on β-strand conformation |
Routinely implemented: challenging data interpretation | Only monovalent | [61,62,63,64,65,66] |
| NIR | Determination of the adsorbed protein content | Exploratory | Only monovalent | [67] |
| CD | Secondary protein structure: focus on α-helix conformation |
Routinely implemented: challenging data interpretation and execution | Only monovalent | [68,69,70] |
| IF | Tertiary protein structure: focus on conformational changes; Determination of the adsorbed protein content: useful for inline process monitoring and HTP analysis. |
Routinely implemented | Only monovalent | [63,64,65,71,72,73,74] |
| EF | Tertiary protein structure: focus on conformational changes. |
Routinely implemented | Only monovalent | [68,75,76] |
| DSC | Tertiary protein structure: focus on thermal stability. |
Routinely implemented | Only monovalent | [77,78,79] |
| NMR | Atomic structural analysis: solid state analysis performed on adsorbed antigen. |
Exploratory | Only monovalent | [80,81] |
| Imaging | Determination of the adsorbed protein content; Antigen distribution/orientation on aluminum adjuvants. |
Exploratory | Mono- and multivalent | [82,83,84] |
| FC | Determination of the adsorbed protein content; Antigen distribution on aluminum adjuvants; Focus on freeze/thaw damage. |
Exploratory | Mono- and multivalent | [85,86,87,88] |
| ELISA/DAFIA | Determination of the adsorbed protein content; Useful for QC analysis: focus on antigenicity, potency, and product consistency. |
Routinely implemented | Mono- and multivalent | [89,90,91,92,93] |
| Raman | Structural fingerprint of complex vaccine products: high specificity and sensitivity. |
Exploratory | Mono- and multivalent | [94] |
| LC–MS | Determination of the adsorbed protein content. | Exploratory | Mono- and multivalent | [95] |