In vivo tissue transparency in the visible light spectrum is beneficial for many research applications that use optical methods, whether it involves in vivo optical imaging of cells or their activity, or optical intervention to affect cells or their activity deep inside tissues, such as brain tissue. The classical view is that a tissue is transparent if it neither absorbs nor scatters light, and thus absorption and scattering are the key elements to be controlled to reach the necessary transparency. This review focuses on the latest genetic and chemical approaches for the decoloration of tissue pigments to reduce visible light absorption and the methods to reduce scattering in live tissues. We also discuss the possible molecules involved in transparency.

Tissue Transparency In Vivo.

Creating advanced properties out of simple building blocks remains a frontier in materials science. Two recent papers report advances to achieve toughening of graphene by mimicking a paradigm found in nature, realizing mechanical resiliency by mixing weak and strong bonding.

Nature’s Way: Hierarchical Strengthening through Weakness

Proteins are key building blocks of virtually all life, providing the material foundation of spider silk, cells, and hair, but also offering other functions from enzymes to drugs, and pathogens like viruses. Based on a nanomechanical analysis of the structure and motions of atoms and molecules at multiple scales, we report sonified versions of the coronavirus spike protein of the pathogen of COVID-19, 2019-nCoV. The audio signal, created using a novel nanomechanical sonification method, features an overlay of the vibrational signatures of the protein's primary, secondary and higher-order structures. Presenting musical encoding in two versions - one in the amino-acid scale and one based on equal temperament tuning - the method allows for expressing protein structures in audible space, offering novel avenues to represent, analyze and design architectural features across length- and time-scales. We further report a hierarchical frequency spectrum analysis of five distinct protein structures, which offer insights into how genetic mutations, and the binding of the virus spike protein to the human ACE2 cell receptor directly influence the audio. Applications of the approach may include the development of de novo antibodies by designing protein sequences that match, through melodic counterpoints, the binding sites in the spike protein. Other applications of audible coding of matter include material design by manipulating sound, detecting mutations, and offering a way to reach out to broader communities to explain the physics of proteins. It also forms a physics-based compositional technique to create new art, referred to as materiomusic, which is akin to finding a new palette of colors for a painter. Here, the nanomechanical structure of matter, reflected in an oscillatory framework, presents a new palette for sound generation, and can complement or support human creativity.

Nanomechanical sonification of the 2019-nCoV coronavirus spike protein through a materiomusical approach

Engineered nasal dry powder for the encapsulation of bioactive compounds.

WebNet: A biomateriomic three-dimensional spider web neural net

Summary The dragonfish is a voracious predator of the deep sea with an arsenal of tools to hunt prey and remain concealed. In contrast to its dark pigmented skin, the dragonfish is equipped with transparent teeth. Here, we establish the structure, composition, and mechanical properties of the transparent teeth for the first time. We find the enamel-like layer to consist of nanocrystalline hydroxyapatite domains (∼20 nm grain size) embedded in an amorphous matrix, whereas in the dentin layer the nanocrystalline hydroxyapatite coats nanoscale collagen fibrils forming nanorods. This nanoscale structure is responsible for the much-reduced Rayleigh light scattering, which is further ensured by the sufficiently thin walls. Here, we suggest that the nanostructured design of the transparent dragonfish teeth enables predatory success as it makes its wide-open mouth armed with saber-like teeth effectively disappear, showing no contrast to the surrounding blackness of the fish nor the background darkness of the deep sea.

On the Nature of the Transparent Teeth of the Deep-Sea Dragonfish, Aristostomias scintillans

Pulmonary delivery of nanocarriers for novel antimycobacterial compounds is challenging because the aerodynamic properties of nanomaterials are sub-optimal for such purposes. Here, we report the development of dry powder formulations for nanocarriers containing benzothiazinone 043 (BTZ) or levofloxacin (LVX), respectively. The intricacy is to generate dry powder aerosols with adequate aerodynamic properties while maintaining both nanostructural integrity and compound activity until reaching the deeper lung compartments. Microparticles (MPs) were prepared using vibrating mesh spray drying with lactose and leucine as approved excipients for oral inhalation drug products. MP morphologies and sizes were measured using various biophysical techniques including determination of geometric and aerodynamic mean sizes, X-ray diffraction, and confocal and focused ion beam scanning electron microscopy. Differences in the nanocarriers' characteristics influenced the MPs' sizes and shapes, their aerodynamic properties, and, hence, also the fraction available for lung deposition. Spay-dried powders of a BTZ nanosuspension, BTZ-loaded silica nanoparticles (NPs), and LVX-loaded liposomes showed promising respirable fractions, in contrast to zirconyl hydrogen phosphate nanocontainers. While the colloidal stability of silica NPs was improved after spray drying, MPs encapsulating either BTZ nanosuspensions or LVX-loaded liposomes showed the highest respirable fractions and active pharmaceutical ingredient loads. Importantly, for the BTZ nanosuspension, biocompatibility and in vitro uptake by a macrophage model cell line were improved even further after spray drying.

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Birgit Nothdurft

Papers

On the Nature of the Transparent Teeth of the Deep-Sea Dragonfish, Aristostomias scintillans

Spray-dried lactose-leucine microparticles for pulmonary delivery of antimycobacterial nanopharmaceuticals.