Chemical mapping of the distribution of viruses into infected bacteria with a photothermal method

Quantifying nanoscale biochemical heterogeneity in human epithelial cancer cells using combined AFM and PTIR absorption nanoimaging

“…These studies indicate that while complex biological systems can be chemically probed with this method, the actual deflection observed is not only a function of the material absorption coefficient, but also of the amount of the absorbing material that is present in the vicinity of the tip [21]. This is likely a significant contributor to the intensity variation observed in previous studies when imaging the same region at different wavelengths [18][19][20][21]. Further to this we illustrate that a combined topographic-IR analysis not only permits chemical discrimination on the nanoscale, but can also give insight into chemical heterogeneity at sub-optical diffraction limited resolution.…”

“…Examining the relationship between cell topography height and absorption enables assessment of chemical heterogenity. This is because absorption scales with the volume of the material contributing to the IR signal [21] only if the material is homogeneous i.e. if it is comprised of consistent biochemical species, possessing in this case a C-H density that correlates with the band analysed.…”

“…This has led to the use of the PTIR technique for absorption imaging and spectroscopy of numerous biomaterials, including lipids [17], proteins [18], bacteria [19] and live cells [20]. When probing small features such as viruses within a host organism [21], the power of the method for discriminating heterogeneous chemical signals far below the optical diffraction limit becomes apparent. ) present in the spectral derivative (1)(2)(3)(4).…”

Nanoscale optical imaging by atomic force infrared microscopy

“…It is noted however, that such mapping is limited in the Z plane. Studies of virus in bacteria demonstrated that viruses present beneath the host surface can be imaged but with undefined resolution [31]. Presently the inability to resolve information in the Z plane is a limit in the imaging ability of AFMIR.…”

“…Localised IR spectra of E. coli were recorded using AFMIR and compared with the spectrum of an assembly of bacteria (measured with a far-field FTICR) which showed the same features. AFMIR was then applied to study Escherichia coli bacteria infected with T5 phage (bacteria virus) [31]. Bacteria E. coli was grown in LB medium to the exponential growth phase and infected by phages, where the virus infection was studied at various stages using AFMIR.…”