Fig. 4.

a) FTIR spectra of representative samples highlighting prominent absorptions bands from the different AlOOH and Tdap formulations, from 1700 cm⁻¹ to 900 cm⁻¹. a1) shows E6020-AlOOH adjuvant (dashed line) and Tdap-E6020-AlOOH formulations; a2) shows CpG-AlOOH adjuvant (dashed line) and Tdap-CpG-AlOOH formulations; a3) shows AlOOH alone (dashed) and Tdap AlOOH controls. Linear baseline correction with 42 iterations was applied to each spectrum to remove baseline drift. All formulations have an Al-O–H bending absorption band (1065 – 1068 cm⁻¹), and all adsorbed samples have peaks in the Amide I (1600–1700 cm⁻¹) and Amide II (1500–1600 cm⁻¹) region. b) FTIR spectra of representative samples of pre-adsorbed antigens and their AlOOH absorbed counterparts, from 1700 cm⁻¹ to 900 cm⁻¹.