Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States.
Pendar Technologies, 30 Spinelli Place, Cambridge, Massachusetts 02138, United States.
Anal Chem. 2022 May 3;94(17):6512-6520. doi: 10.1021/acs.analchem.1c05504. Epub 2022 Apr 21.
Label-free autofluorescence-detected photothermal mid-IR (AF-PTIR) microscopy is demonstrated experimentally and applied to test the distribution of active pharmaceutical ingredients (APIs) in a mixture containing representative pharmaceutical excipients. Two-photon excited UV-fluorescence (TPE-UVF) supports autofluorescence of native aromatic moieties using visible-light optics. Thermal modulation of the fluorescence quantum yield serves to report on infrared absorption, enabling infrared spectroscopy in the fingerprint region with a spatial resolution dictated by fluorescence. AF-PTIR provides high selectivity and sensitivity in image contrast for aromatic APIs, complementing broadly applicable optical photothermal IR (O-PTIR) microscopy based on photothermal modulation of refractive index/scattering. Mapping the API distribution is critical in designing processes for powdered dosage form manufacturing, with high spatial variance potentially producing variability in both delivered dosage and product efficacy. The ubiquity of aromatic moieties within API candidates suggests the viability of AF-PTIR in combination with O-PTIR to improve the confidence of chemical classification in spatially heterogeneous dosage forms.
无标记自发荧光探测光热中红外（AF-PTIR）显微镜在实验中得到了验证，并应用于测试含有代表性药物赋形剂的混合物中活性药物成分（API）的分布。双光子激发紫外荧光（TPE-UVF）使用可见光光学支持本征芳香基团的自发荧光。荧光量子产率的热调制可用于报告红外吸收，从而在指纹区域进行红外光谱测量，其空间分辨率由荧光决定。AF-PTIR 为芳香族 API 提供了高选择性和高灵敏度的图像对比度，补充了基于折射率/散射光热调制的广泛适用的光学光热红外（O-PTIR）显微镜。在设计粉末剂型制造工艺时，绘制 API 分布至关重要，因为高空间变异性可能会导致给药剂量和产品功效产生变化。在 API 候选物中普遍存在芳香基团，这表明 AF-PTIR 与 O-PTIR 相结合具有提高空间不均匀剂型化学分类置信度的可行性。
