Direct Observation of the Distribution of Gelatin in Calcium Carbonate Crystals by Super-Resolution Fluorescence Microscopy

Spatial mapping and quantitative evaluation of protein corona on PEGylated mesoporous silica particles by super-resolution fluorescence microscopy

Nanoparticles (NPs) adsorb serum proteins when exposed to biological fluids, forming a dynamic protein corona that has a profound impact on their overall biological profile and fate. Polyethylene glycol (PEG) modification is the most widely used strategy to mitigate and inhibit protein corona formation. Nevertheless, the accurate mapping and quantification of PEG inhibition effects on protein corona formation have scarcely been reported. Herein, we demonstrate the direct observation and quantification of protein corona adsorbed onto PEGylated mesoporous silica particles by direct stochastic optical reconstruction microscopy (dSTORM). The variation tendency of protein penetration depth in terms of PEG molecular weights and incubated time is investigated for the first time. The maximum penetration depths present slight increase with the prolonged incubation time, while they tend to remarkably decrease with increased chain length of modified PEG. Moreover, the co-localization of preformed protein corona with lysosomes and the destination of adsorbed protein are demonstrated. Our method provides important technical characterization information and in-depth understanding of protein corona adsorbed onto PEGylated mesoporous silica particles. This shines new light on the behaviors of silica materials in cells and may promote their practical applications in biomedicine.

The power of super-resolution microscopy in modern biomedical science

Super-resolution microscopy (SRM) technology that breaks the diffraction limit has revolutionized the field of cell biology since its appearance, which enables researchers to visualize cellular structures with nanometric resolution, multiple colors and single-molecule sensitivity. With the flourishing development of hardware and the availability of novel fluorescent probes, the impact of SRM has already gone beyond cell biology and extended to nanomedicine, material science and nanotechnology, and remarkably boosted important breakthroughs in these fields. In this review, we will mainly highlight the power of SRM in modern biomedical science, discussing how these SRM techniques revolutionize the way we understand cell structures, biomaterials assembly and how assembled biomaterials interact with cellular organelles, and finally their promotion to the clinical pre-diagnosis. Moreover, we also provide an outlook on the current technical challenges and future improvement direction of SRM. We hope this review can provide useful information, inspire new ideas and propel the development both from the perspective of SRM techniques and from the perspective of SRM's applications.

Novel Colloidal Dispersing Concept in Aqueous Media for Preparation by Wet-Jet Milling Dispersing Method

Dispersing particles in a liquid phase is significant for producing various functional nano/bio applications. The wet-jet milling method has been gaining attention as an attractive dispersing method in the preparation of soft material suspensions. This is because the main driving force of dispersion by the wet-jet milling method is the shear force, which is weaker than that it is in the ultrasonication dispersing method. In the wet-jet milling method, the pressure of the narrow channel which the liquid is passes through and the number of passes are used as the control parameters for dispersing the particles. However, the values of the pressure depend on the size (diameter and length) of the narrow channel, thus, it is not a commonly used dispersing parameter in dispersing by wet-jet milling to set the dispersing condition by various wet-jet milling instruments. In addition, wet-jet milling users must optimize the dispersing conditions such as the pressure and number of passes in the narrow channel, therefore, a simple prediction/optimization method of the dispersing size by the wet-jet milling method is desired. In this study, we established a novel colloidal dispersing concept, the dispersing energy input based on a calorimetric idea, for particle suspension preparation using the wet-jet milling method. The dispersing energy input by wet-jet milling was quantitatively calculated under various conditions during the dispersing by wet-jet milling, and then, the dispersing size of the particles was easily predicted/optimized. We demonstrated the usability of the concept by preparing aqueous suspensions of calcium carbonate (CaCO₃) particles with various surfactants using the wet-jet milling method. Based on the established concept, in a case study on dispersing CaCO₃, we found that changes in the micelle sizes of the surfactants played a role in wet-jet milling. The novel idea of the representation of energy input makes it possible to estimate the appropriate condition of the dispersing process by wet-jet milling to control the size of particles.

Assembly and Applications of Macrocyclic-Confinement-Derived Supramolecular Organic Luminescent Emissions from Cucurbiturils

Cucurbit[n]urils (Q[n]s or CB[n]s), as a classical of artificial organic macrocyclic hosts, were found to have excellent advantages in the fabricating of tunable and smart organic luminescent materials in aqueous media and the solid state with high emitting efficiency under the rigid pumpkin-shaped structure-derived macrocyclic-confinement effect in recent years. This review aims to give a systematically up-to-date overview of the Q[n]-based supramolecular organic luminescent emissions from the confined spaces triggered host-guest complexes, including the assembly fashions and the mechanisms of the macrocycle-based luminescent complexes, as well as their applications. Finally, challenges and outlook are provided. Since this class of Q[n]-based supramolecular organic luminescent emissions, which have essentially derived from the cavity-dependent confinement effect and the resulting assembly fashions, emerged only a few years ago, we hope this review will provide valuable information for the further development of macrocycle-based light-emitting materials and other related research fields.

In vitro crystallization of calcium carbonate mediated by proteins extracted from P. placenta shells

The ASM extracted from the shells of P. placenta can stabilize ACC and inhibit secondary nucleation for 10 hours, and an explosive secondary nucleation and quick crystal growth from 50 nm to 10 μm can be finished on the shell surface in one hour.

Dopamine-Mediated Biomineralization of Calcium Phosphate as a Strategy to Facilely Synthesize Functionalized Hybrids

Organic-inorganic hybrid materials have been considered to be promising carriers or immobilization matrixes for biomolecules due to their high efficiency and significantly enhanced activities and stabilities of biomolecules. Here, the well-defined dopamine/calcium phosphate organic-inorganic hybrids (DACaPMFs) are fabricated via one-pot dopamine-mediated biomineralization, and their structure and properties are also characterized. Direct stochastic optical reconstruction microscopy (dSTORM) is first used to probe the distribution of organic components in these hybrids. Combined with spectroscopic data, the direct observation of dopamine in the hybrids helps to understand the formation of a physical chemistry mechanism of the biomineralization. The obtained DACaPMFs with multiple-level pores allow the loading of doxorubicin with a high loading efficiency and a pH-responsive property. Furthermore, thrombin is entrapped by the hybrids to prove the controlled release. It is expected that such organic-inorganic hybrid materials may hold great promise for application in drug delivery as well as scaffold materials in bone tissue engineering and hemostatic material.

Pollen-inspired enzymatic microparticles to reduce organophosphate toxicity in managed pollinators

Pollinators support the production of the leading food crops worldwide. Organophosphates are a heavily used group of insecticides that pollinators can be exposed to, especially during crop pollination. Exposure to lethal or sublethal doses can impair fitness of wild and managed bees, risking pollination quality and food security. Here we report a low-cost, scalable in vivo detoxification strategy for organophosphate insecticides involving encapsulation of phosphotriesterase (OPT) in pollen-inspired microparticles (PIMs). We developed uniform and consumable PIMs capable of loading OPT at 90% efficiency and protecting OPT from degradation in the pH of a bee gut. Microcolonies of Bombus impatiens fed malathion-contaminated pollen patties demonstrated 100% survival when fed OPT-PIMs but 0% survival with OPT alone, or with plain sucrose within five and four days, respectively. Thus, the detrimental effects of malathion were eliminated when bees consumed OPT-PIMs. This design presents a versatile treatment that can be integrated into supplemental feeds such as pollen patties or dietary syrup for managed pollinators to reduce risk of organophosphate insecticides.

PU14, a Novel Matrix Protein, Participates in Pearl Oyster, Pinctada Fucata, Shell Formation

Biomineralization is a widespread biological process, involved in the formation of shells, teeth, and bones. Shell matrix proteins have been widely studied for their importance during shell formation. In 2015, our group identified 72 unique shell matrix proteins in Pinctada fucata, among which PU14 is a matrix protein detected in the soluble fraction that solely exists in the prismatic layer. However, the function of PU14 is still unclear. In this study, the full-length cDNA sequence of PU14 was obtained and functional analyses of PU14 protein during shell formation were performed. The deduced protein has a molecular mass of 77.8 kDa and an isoelectric point of 11.34. The primary protein structure contains Gln-rich and random repeat units, which are typical characteristics of matrix protein and indicate its potential function during shell formation. In vivo and in vitro experiments indicated PU14 has prismatic layer functions during shell formation. The tissue expression patterns showed that PU14 was mainly expressed in the mantle tissue, which is consistent with prismatic layer formation. Notching experiments suggested that PU14 responded to repair and regenerate the injured shell. After inhibiting gene expression by injecting PU14-specific double-stranded RNA, the inner surface of the prismatic layer changed significantly and became rougher. Further, in vitro experiments showed that recombinant protein rPU14 impacted calcite crystal morphology. Taken together, characterization and functional analyses of a novel matrix protein, PU14, provide new insights about basic matrix proteins and their functions during shell formation.

Fluorescence visualization of cucurbit[8]uril-triggered dynamic host–guest assemblies

Dynamic assemblies of π-conjugated bispyridinium guests with cucurbit[8]uril in aqueous solution could be distinguished by real-time naked-eye observation of the resulting quantitative fluorescence emissions.

Dynamic Detection of Active Enzyme Instructed Supramolecular Assemblies In Situ via Super-Resolution Microscopy

Inspired by the self-assembly phenomena in nature, the instructed self-assembly of exogenous small molecules in a biological environment has become a prevalent process to control cell fate. Despite mounting examples of versatile bioactivities, the underlying mechanism remains less understood, which is in large hindered by the difficulties in the identification of those dynamic assemblies in situ. Here, with direct stochastic optical reconstruction microscopy, we are able to elucidate the dynamic morphology transformation of the enzyme-instructed supramolecular assemblies in situ inside cancer cells with a resolution below 50 nm. It indicates that the assembling molecules endure drastically different pathways between cell lines with different phosphatase activities and distribution. In HeLa cells, the direct formation of intracellular supramolecular nanofibers showed slight cytotoxicity, which was due to the possible cellular secretory pathway to excrete those exogenous molecules assemblies. In contrast, in Saos-2 cells with active phosphatase on the cell surface, assemblies with granular morphology first formed on the cell membranes, followed by a transformation into nanofibers and accumulation in cells, which induced Saos-2 cell death eventually. Overall, we provided a convenient method to reveal the in situ dynamic nanomorphology transformation of the supramolecular assemblies in a biological environment, in order to decipher their diverse biological activities.

Super-Resolution Microscopy Reveals Shape and Distribution of Dislocations in Single-Crystal Nanocomposites

With their potential to offer new properties, single crystals containing nanoparticles provide an attractive class of nanocomposite materials. However, to fully profit from these, it is essential that we can characterise their 3D structures, identifying the locations of individual nanoparticles, and the defects present within the host crystals. Using calcite crystals containing quantum dots as a model system, we here use 3D stochastic optical reconstruction microscopy (STORM) to locate the positions of the nanoparticles within the host crystal. The nanoparticles are shown to preferentially associate with dislocations in a manner previously recognised for atomic impurities, rendering these defects visible by STORM. Our images also demonstrate that the types of dislocations formed at the crystal/substrate interface vary according to the nucleation face, and dislocation loops are observed that have entirely different geometries to classic misfit dislocations. This approach offers a rapid, easily accessed, and non-destructive method for visualising the dislocations present within crystals, and gives insight into the mechanisms by which additives become occluded within crystals.

A basic protein, N25, from a mollusk modifies calcium carbonate morphology and shell biomineralization

Biomineralization is a widespread biological process in the formation of shells, teeth, or bones. Matrix proteins in biominerals have been widely investigated for their roles in directing biomineralization processes such as crystal morphologies, polymorphs, and orientations. Here, we characterized a basic matrix protein, named mantle protein N25 (N25), identified previously in the Akoya pearl oyster (Pinctada fucata). Unlike some known acidic matrix proteins containing Asp or Glu as possible Ca²⁺-binding residues, we found that N25 is rich in Pro (12.4%), Ser (12.8%), and Lys (8.8%), suggesting it may perform a different function. We used the recombinant protein purified by refolding from inclusion bodies in a Ca(HCO₃)₂ supersaturation system and found that it specifically affects calcite morphologies. An X-ray powder diffraction (XRD) assay revealed that N25 could help delay the transformation of vaterites (a metastable calcium carbonate polymorph) to calcite. We also used fluorescence super-resolution imaging to map the distribution of N25 in CaCO₃ crystals and transfected a recombinant N25-EGFP vector into HEK-293T cells to mimic the native process in which N25 is secreted by mantle epithelial cells and integrated into mineral structures. Our observations suggest N25 specifically affects crystal morphologies and provide evidence that basic proteins lacking acidic groups can also direct biomineralization. We propose that the attachment of N25 to specific sites on CaCO₃ crystals may inhibit some crystal polymorphs or morphological transformation.

Monitoring drug nanocarriers in human blood by near-infrared fluorescence correlation spectroscopy

Nanocarrier-based drug delivery is a promising therapeutic approach that offers unique possibilities for the treatment of various diseases. However, inside the blood stream, nanocarriers' properties may change significantly due to interactions with proteins, aggregation, decomposition or premature loss of cargo. Thus, a method for precise, in situ characterization of drug nanocarriers in blood is needed. Here we show how the fluorescence correlation spectroscopy that is a well-established method for measuring the size, loading efficiency and stability of drug nanocarriers in aqueous solutions can be used to directly characterize drug nanocarriers in flowing blood. As the blood is not transparent for visible light and densely crowded with cells, we label the nanocarriers or their cargo with near-infrared fluorescent dyes and fit the experimental autocorrelation functions with an analytical model accounting for the presence of blood cells. The developed methodology contributes towards quantitative understanding of the in vivo behavior of nanocarrier-based therapeutics.