Infrared nanoimaging of neuronal ultrastructure and nanoparticle interaction with cells

Here we introduce scattering-type scanning near-field optical microscopy (s-SNOM) as a novel tool for nanoscale chemical-imaging of sub-cellular organelles, nanomaterials and of the interactions between them. Our setup uses a tuneable mid-infrared laser and a sharp scanning probe to image at a resolution substantially surpassing the diffraction limit. The laser can be tuned to excite vibrational modes of functional groups in biomolecules, (e.g. amide moieties), in a way that enables direct chemical mapping without the need for labelling. We, for the first time, chemically image neuronal ultrastructure, identify neuronal organelles and sub-organelle structures as small as 10 nm and validate our findings using transmission electron microscopy (TEM). We produce chemical and morphological maps of neurons treated with gold nanospheres and characterize nanoparticle size and intracellular location, and their interaction with the plasma membrane. Our results show that the label-free nature of s-SNOM means it has a 'true' chemical resolution of up to 20 nm which can be further improved. We argue that it offers significant potential in nanomedicine for nanoscale chemical imaging of cell ultrastructure and the subcellular distribution of nanomaterials within tissues.

Label-free nanoscale mapping of intracellular organelle chemistry

The ability to image cell chemistry at the nanoscale is key for understanding cell biology, but many optical microscopies are restricted by the ~(200-250)nm diffraction limit. Electron microscopy and super-resolution fluorescence techniques beat this limit, but rely on staining and specialised labelling to generate image contrast. It is challenging, therefore, to obtain information about the functional chemistry of intracellular components. Here we demonstrate a technique for intracellular label-free chemical mapping with nanoscale (~30 nm) resolution. We use a probe-based optical microscope illuminated with a mid-infrared laser whose wavelengths excite vibrational modes of functional groups occurring within biological molecules. As a demonstration, we chemically map intracellular structures in human multiple myeloma cells and compare the morphologies with electron micrographs of the same cell line. We also demonstrate label-free mapping at wavelengths chosen to target the chemical signatures of proteins and nucleic acids, in a way that can be used to identify biochemical markers in the study of disease and pharmacology.

A95 OUTCOMES OF ERCP UNDER CONSCIOUS SEDATION COMPARED TO GENERAL ANESTHESIA: A PRE-POST RETROSPECTIVE COHORT REVIEW

Background

Endoscopic retrograde cholangiopancreatography (ERCP) is a diagnostic and therapeutic procedure used to address pathologies of the pancreatic and biliary systems. ERCP performed under conscious sedation (CS) is the current standard of care but is limited by patient movement and agitation, especially in the context of lengthy or technically complex cases. Recent literature suggests that general anesthesia (GA) may optimize patient comfort and safety while reducing complications such as pancreatitis, perforation, and mortality. In October 2017, Kelowna General Hospital (KGH) transitioned the standard anesthesia modality for ERCP from CS to GA.

Aims

To investigate differences in complications and patient outcomes for ERCP performed under CS (n=1334) before the practice change compared to GA (n=899) after the practice change.

Methods

Our study is a pre-post retrospective chart review of 2,233 patients who underwent ERCP between 2015 and 2020 at KGH. Demographic, clinical, procedural and outcome data were extracted from patient charts, and the data in CS and GA groups were compared using univariate statistical analysis.

Results

Preliminary results show rates of post-ERCP pancreatitis (6% vs. 4%; p=0.018) and rates of procedure failure (8% vs. 3%; p<0.001) were statistically significant and higher under CS before the practice change compared to under GA afterwards, respectively. The 30-day mortality rates, ICU transfer rates, return rates post-discharge, and rates of cholangitis were similar.

Our study showed improvements in several patient safety outcomes, including lower procedure failure rates and lower post-ERCP pancreatitis rates with ERCP performed under GA compared to CS.

Conclusions

Performing ERCP under GA rather than under CS is a valuable practice change that should be considered by ERCP-related programs across all health authorities due to its potential to optimize both patient comfort and safety significantly. The reduction in complication rates may have implications for net cost savings in the long term.

Funding Agencies

Kelowna General Hospital Foundation, Interior Health