The study of growth and possible metastasis in animal models of tumors would benefit from reliable cell labels for noninvasive whole-organism imaging techniques such as magnetic resonance imaging. Genetically encoded cell-tracking reporters have the advantage that they are contrast-selective for viable cells with intact protein expression machinery. Besides, these reporters do not suffer from dilution during cell division. Encapsulins, which are bacterial protein nanocompartments, can serve as genetically controlled labels for multimodal detection of cells. Such nanocompartments can host various guest molecules inside their lumen. These include, for example, fluorescent proteins or enzymes with ferroxidase activity leading to biomineralization of iron oxide inside the encapsulin nanoshell. The aim of this work was to implement heterologous expression of encapsulin systems from Quasibacillus thermotolerans using the fluorescent reporter protein mScarlet-I and ferroxidase IMEF in the human hepatocellular carcinoma cell line HepG2. The successful expression of self-assembled encapsulin nanocompartments with functional cargo proteins was confirmed by fluorescence microscopy and transmission electron microscopy. Also, coexpression of encapsulin nanoshells, ferroxidase cargo, and iron transporter led to an increase in T2-weighted contrast in magnetic resonance imaging of HepG2 cells. The results demonstrate that the encapsulin cargo system from Q. thermotolerans may be suitable for multimodal imaging of cancer cells and could contribute to further in vitro and in vivo studies.

A prominent goal of neuroscience is to improve our understanding of how brain structure and activity interact to produce perception, emotion, behavior, and cognition. The brain’s network activity is inherently organized in distinct spatiotemporal patterns that span scales from nanometer-sized synapses to meter-long nerve fibers and millisecond intervals between electrical signals to decades of memory storage. There is currently no single imaging method that alone can provide all the relevant information, but intelligent combinations of complementary techniques can be effective. Here, we thus present the latest advances in biomedical and biological engineering on photoacoustic neuroimaging in the context of complementary imaging techniques. A particular focus is placed on recent advances in whole-brain photoacoustic imaging in rodent models and its influential role in bridging the gap between fluorescence microscopy and more non-invasive techniques such as magnetic resonance imaging (MRI). We consider current strategies to address persistent challenges, particularly in developing molecular contrast agents, and conclude with an overview of potential future directions for photoacoustic neuroimaging to provide deeper insights into healthy and pathological brain processes.

Degenerative alterations of the spine occur in an individual-specific manner with increasing age. This is not only dependent on external factors, such as hard physical labor over many years but can also be genetically influenced as demonstrated in recent studies. The spinal cord is well-protected within the spinal canal but can be impaired by degenerative alterations of the intervertebral discs and functional spinal segments. Depositions or narrowing of nerve structures can cause lasting pain or focal neurological deficits, such as paralysis or sensitivity disorders. These complaints can slowly develop over years, e.g. by a gradually increasing bony narrowing of the spinal canal (spinal canal stenosis) or can occur suddenly, e.g. an acute herniated disc. However, low back pain is much more common and occurs in approximately 80 % of people sometime during their lifetime. It is necessary to recognize the normal age-related anatomical alterations in magnetic resonance imaging (MRI), particularly for intervertebral discs in order to interpret these correctly. Knowledge of the spectrum of the various age-related degenerative processes which can occur in intervertebral discs and vertebral bodies is necessary to be able to differentiate them from pathological alterations. This is important because therapy decisions are often made as a direct result of MRI.