Correlative light-electron microscopy using small gold nanoparticles as single probes

Effective alignment method using a diamond notch knife for correlative array tomography

Correlative array tomography, combining light and electron microscopy via serial sections, plays a crucial role in the three-dimensional ultrastructural visualization and molecular distribution analysis in biological structures. To address the challenges of aligning fluorescence and electron microscopy images and aligning serial sections of irregularly shaped biological specimens, we developed a diamond notch knife, a new tool for puncturing holes using a diamond needle. The diamond needle featured a triangular and right-angled tip, enabling the drilling of deep holes upon insertion into the polished block face. This study describes the application of the diamond notch knife in correlative array tomography.

Beyond the Gut: The intratumoral microbiome's influence on tumorigenesis and treatment response

The intratumoral microbiome (TM) refers to the microorganisms in the tumor tissues, including bacteria, fungi, viruses, and so on, and is distinct from the gut microbiome and circulating microbiota. TM is strongly associated with tumorigenesis, progression, metastasis, and response to therapy. This paper highlights the current status of TM. Tract sources, adjacent normal tissue, circulatory system, and concomitant tumor co-metastasis are the main origin of TM. The advanced techniques in TM analysis are comprehensively summarized. Besides, TM is involved in tumor progression through several mechanisms, including DNA damage, activation of oncogenic signaling pathways (phosphoinositide 3-kinase [PI3K], signal transducer and activator of transcription [STAT], WNT/β-catenin, and extracellular regulated protein kinases [ERK]), influence of cytokines and induce inflammatory responses, and interaction with the tumor microenvironment (anti-tumor immunity, pro-tumor immunity, and microbial-derived metabolites). Moreover, promising directions of TM in tumor therapy include immunotherapy, chemotherapy, radiotherapy, the application of probiotics/prebiotics/synbiotics, fecal microbiome transplantation, engineered microbiota, phage therapy, and oncolytic virus therapy. The inherent challenges of clinical application are also summarized. This review provides a comprehensive landscape for analyzing TM, especially the TM-related mechanisms and TM-based treatment in cancer.

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.

Some tips and tricks for a Correlative Light Electron Microscopy workflow using stable expression of fluorescent proteins

Correlative Light Electron Microscopy (CLEM) encompasses a wide range of experimental approaches with different degrees of complexity and technical challenges where the attributes of both light and electron microscopy are combined in a single experiment. Although the biological question always determines what technology is the most appropriate, we generally set out to apply the simplest workflow possible. For 2D cell cultures expressing fluorescently tagged molecules, we report on a simple and very powerful CLEM approach by using gridded finder imaging dishes. We first determine the gross localization of the fluorescence using light microscopy and subsequently we retrace the origin/localization of the fluorescence by projecting it onto the ultrastructural reference space obtained by transmission electron microscopy (TEM). Here we describe this workflow and highlight some basic principles of the sample preparation for such a simple CLEM experiment. We will specifically focus on the steps following the resin embedding for TEM and the introduction of the sample in the electron microscope.

Some Guiding Principles for a "Simple" Correlative Light Electron Microscopy Experiment

In recent years, Correlative Multimodal Imaging (CMI) has become an "en vogue" technique and a bit of a buzzword. It entails combining information from different imaging modalities to extract more information from a sample that would otherwise not be possible from each individual technique. The best established CMI technology is correlative light and electron microscopy (CLEM), which applies light and electron microscopy on the exact same sample/structure. In general, it entails the detection of fluorescently tagged proteins or structures by light microscopy and subsequently their relative intracellular localization is determined with nanometer resolution using transmission electron microscopy (TEM). Here, we describe the different steps involved in a "simple" CLEM approach. We describe the overall workflow, instrumentation, and basic principles of sample preparation for a CLEM experiment exploiting stable expression of fluorescent proteins.

Correlative Imaging to Detect Rare HIV Reservoirs and Associated Damage in Tissues

Correlative light-electron microscopy (CLEM) has evolved in the last decades, especially after significant developments in sample preparation, imaging acquisition, software, spatial resolution, and equipment, including confocal, live-cell, super-resolution, and electron microscopy (scanning, transmission, focused ion beam, and cryo-electron microscopy). However, the recent evolution of different laser-related techniques, such as mass spectrometry imaging (MSI) and laser capture microdissection, could further expand spatial imaging capabilities into high-resolution OMIC approaches such as proteomic, lipidomics, small molecule, and drug discovery. Here, we will describe a protocol to integrate the detection of rare viral reservoirs with imaging mass spectrometry.

Single probes and resonant four-wave-mixing enabling novel correlative light electron microscopy workflow

Correlative light electron microscopy prefers single probes with stable performance in both optical and electron microscopy. Now researchers have shown how to harness gold nanoparticles featuring exceptional photostability and four-wave-mixing nonlinearity to realize a new correlation imaging approach.