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Carbene-based macromolecules are an emerging new stimuli-sensitive class of biomaterials that avoid the impediments of free radical polymerization but maintain a rapid liquid-to-biorubber transition. Activation of diazirine-grafted polycaprolactone polyol (CaproGlu) is limited to UVA wavelengths that have tissue exposure constraints and limited light intensities. For the first time, UVA is circumvented with visible light-emitting diodes at 445 nm (blue) to rapidly activate diazirine-to-carbene covalent cross-linking. Iridium photocatalysts serve to initiate diazirine, despite having little to no absorption at 445 nm. CaproGlu’s liquid organic matrix dissolves the photocatalyst with no solvents required, creating a light transparent matrix. Considerable differences in cross-linking chemistry are observed in UVA vs visible/photocatalyst formulations. Empirical analysis and theoretical calculations reveal a more efficient conversion of diazirine directly to carbene with no diazoalkane intermediate detected. Photorheometry results demonstrate a correlation between shear moduli, joules light dose, and the lower limits of photocatalyst concentration required for the liquid-to-biorubber transition. Adhesion strength on ex vivo hydrated tissues exceeds that of cyanoacrylates, with a fixation strength of up to 20 kg·f·cm2. Preliminary toxicity assessment on leachates and materials directly in contact with mammalian fibroblast cells displays no signs of fibroblast cytotoxicity.

The quest to develop ideal nanoparticles capable of molecular, cellular, and tissue level imaging is ongoing. Since certain imaging probes and nanoparticles face drawbacks such as low aqueous solubility, increased ROS generation leading to DNA damage, apoptosis, and high cellular/organ toxicities, the development of versatile and biocompatible nanocarriers becomes necessary. Protein nanoparticles (PNPs) are one such promising class of nanocarriers that possess most of the desirable properties of an ideal nanocarrier for bioimaging applications. PNPs demonstrate high aqueous solubility, minimal cytotoxicity, and multi‐cargo loading capacity. They are also amenable to surface‐functionalization, as well as modulation of their hydrophobicity and hydrophilicity. The use of PNPs for bioimaging applications has made rapid advancements in the past two decades. Being comparatively less explored, the field opens up a plethora of opportunities and focus areas to engineer ideal bioimaging protein nanocarriers. The use of PNPs as carriers of their natural ligands as well as other heavy metals and fluorescent probes, along with drug molecules for combined theranostic applications has been reported. In addition, surface functionalization to impart specificity of targeting the PNPs has been shown to reduce nonspecific cellular interactions, thus reducing systemic toxicity. PNPs have been explored for their application in imaging of numerous cancers, cardiovascular diseases as well as imaging of the brain using near infrared fluorescence (NIRF) imaging, magnetic resonance imaging (MRI), X‐ray computed tomography (CT), positron emission tomography (PET), single‐photon emission computed tomography (SPECT), ultrasound (US), and photoacoustic (PA) imaging. This article is categorized under: Biology‐Inspired Nanomaterials > Protein and Virus‐Based Structures Diagnostic Tools > In Vivo Nanodiagnostics and Imaging

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