Biomineralization of skeletal components (e.g., bone and teeth) is generally accepted to occur under strict cellular regulation, leading to mineral–organic composites with hierarchical structures and ...properties optimized for their designated function. Such cellular regulation includes promoting mineralization at desired sites as well as inhibiting mineralization in soft tissues and other undesirable locations. In contrast, pathological mineralization, with potentially harmful health effects, can occur as a result of tissue or metabolic abnormalities, disease, or implantation of certain biomaterials. This progress report defines mineralization pathway components and identifies the commonalities (and differences) between physiological (e.g., bone remodeling) and pathological calcification formation pathways, based, in part, upon the extent of cellular control within the system. These concepts are discussed in representative examples of calcium phosphate‐based pathological mineralization in cancer (breast, thyroid, ovarian, and meningioma) and in cardiovascular disease. In‐depth mechanistic understanding of pathological mineralization requires utilizing state‐of‐the‐art materials science imaging and characterization techniques, focusing not only on the final deposits, but also on the earlier stages of crystal nucleation, growth, and aggregation. Such mechanistic understanding will further enable the use of pathological calcifications in diagnosis and prognosis, as well as possibly provide insights into preventative treatments for detrimental mineralization in disease.
Physiological biomineralization is a tightly regulated process characterized by multiple levels of synchronized cellular controls. In contrast, pathological calcification, occurring in nonskeletal tissues including vasculature and cancers, occurs via multiple pathways, with varying degrees of cellular regulation. Identifying “pathway components,” e.g., cell death, mineralization proteins, vesicle secretion, and mineralized collagen, provides a framework which is used to describe pathological mineralization pathways.
Abstract The nanoscale materials properties of bone apatite crystals have been implicated in breast cancer bone metastasis and their interactions with extracellular matrix proteins are likely ...involved. In this study, we used geologic hydroxyapatite (HAP, Ca10 (PO4 ) 6OH 2 ), closely related to bone apatite, to investigate how HAP surface chemistry and nano/microscale topography individually influence the crystal-protein interface, and how the altered protein deposition impacts subsequent breast cancer cell activities. We first utilized Förster resonance energy transfer (FRET) to assess the molecular conformation of fibronectin (Fn), a major extracellular matrix protein upregulated in cancer, when it adsorbed onto HAP facets. Our analysis reveals that both low surface charge density and nanoscale roughness of HAP facets individually contributed to molecular unfolding of Fn. We next quantified cell adhesion and secretion on Fn-coated HAP facets using MDA-MB-231 breast cancer cells. Our data show elevated proangiogenic and proinflammatory secretions associated with more unfolded Fn adsorbed onto nano-rough HAP facets with low surface charge density. These findings not only deconvolute the roles of crystal surface chemistry and topography in interfacial protein deposition but also enhance our knowledge of protein-mediated breast cancer cell interactions with apatite, which may be implicated in tumor growth and bone metastasis.
Phase-pure bismuth ferrites (BiFeO3 and Bi2Fe4O9) are grown using hydrothermal synthesis. In addition to varying the KOH, bismuth, and iron salt concentrations to tune which crystalline phases are ...formed, we identified that a 48h, pre-furnace, room temperature reaction is critical for the formation of phase-pure BiFeO3. To understand the reaction pathways leading to the different bismuth ferrite phases, we investigate the changes in composition of the intermediate products as a function of reagent concentrations and room temperature reaction times. During the syntheses that included a room temperature reaction, Bi25FeO40 is formed in the intermediate products, and BiFeO3 is the majority phase of the final products. The BiFeO3 crystals grown using this method are clusters of faceted subunits. These results indicate that forming Bi25FeO40 is a productive route to the formation of BiFeO3. Bi2Fe4O9 is formed via an alternate reaction pathway that proceeded via an amorphous precursor. This improved understanding of how hydrothermal synthesis can be used to control the phase-purity and morphology of bismuth ferrites opens doors to explore the multiferroic properties of BiFeO3 with complex morphologies.
•We developed a robust and tunable synthesis of phase-pure BiFeO3 and Bi2Fe4O9.•A pre-furnace, room temperature reaction is critical for forming phase-pure BiFeO3.•BiFeO3 forms via Bi25FeO40, while Bi2Fe4O9 forms via an amorphous precursor.•The BiFeO3 crystals grown using this method are clusters of faceted subunits.
Hydroxyapatite (HAP, Ca10(PO4)6(OH)2) nanoparticles with controlled materials properties have been synthesized through a two-step hydrothermal aging method to investigate fibronectin (Fn) adsorption. ...Two distinct populations of HAP nanoparticles have been generated: HAP1 particles had smaller size, plate-like shape, lower crystallinity, and more negative ζ potential than HAP2 particles. We then developed two-dimensional platforms containing HAP and Fn and analyzed both the amount and the conformation of Fn via Förster resonance energy transfer (FRET) at various HAP concentrations. Our FRET analysis reveals that larger amounts of more compact Fn molecules were adsorbed onto HAP1 than onto HAP2 particles. Additionally, our data show that the amount of compact Fn adsorbed increased with increasing HAP concentration due to the formation of nanoparticle agglomerates. We propose that both the surface chemistry of single nanoparticles and the size and morphology of HAP agglomerates play significant roles in the interaction of Fn with HAP. Collectively, our findings suggest that the HAP-induced conformational changes of Fn, a critical mechanotransducer protein involved in the communication of cells with their environment, will ultimately affect downstream cellular behaviors. These results have important implications for our understanding of organic–inorganic interactions in physiological and pathological biomineralization processes such as HAP-related inflammation.
We report the room temperature formation of aminated mesoporous silica nanoparticles (NH2-MSNs) by means of co-condensation of different molar ratios of tetraethyl orthosilicate (TEOS) and ...3-aminopropyl triethoxysilane (APTES) in the synthesis feed. The resulting materials are characterized by a combination of transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and N2 adsorption/desorption measurements. Analysis reveals that an increase in APTES loading (mol %) leads to structural transitions in the MSNs from hexagonal (0–49 mol %) to cubic Pm3̅n (54–64 mol %) to disordered at very high APTES amounts (69 mol %). Investigation of structural evolution during cubic Pm3̅n particle synthesis reveals early particle formation stages that are surprisingly similar to those discussed in recent literature on nonclassical single crystal growth. These include significant heterogeneities in particle density despite crystallographic orientation across the entire particle as well as particle growth via addition of preformed and prestructured silica clusters. Syntheses at varying pH reveal further details of the structure formation process. The results pose fundamental questions about the relation between formation mechanisms of classical crystalline materials and mesoscopically ordered, locally amorphous materials.
The design of artificial models of the processes of biomineralization has resulted in the union of inorganic materials research and supramolecular organic chemistry. Recent work in this field of ...bioinspired synthesis of composite organic/inorganic materials is reviewed and prospects for the future are discussed. Attention is focused on the use of self-assembled organic superstructures to template inorganic materials with controlled morphologies.
Despite advances in nanomaterials synthesis, the bottom-up preparation of nanopatterned films as templates for spatially confined surface reactions remains a challenge. We report an approach to ...fabricating nanoscale thin film surface structures with periodicities on the order of 20 nm and with the capacity to localize reactions with small molecules and nanoparticles. A block copolymer (BCP) of polystyrene-block-poly(allyl glycidyl ether)-co-(ethylene oxide) (PS-b-P(AGE-co-EO)) is used to prepare periodically ordered, reactive thin films. As proof-of-principle demonstrations of the versatility of the chemical functionalization, a small organic molecule, an amino acid, and ultrasmall silica nanoparticles are selectively attached via thiol–ene click chemistry to the exposed P(AGE-co-EO) domains of the BCP thin film. Our approach employing click chemistry on the spatially confined reactive surfaces of a BCP thin film overcomes solvent incompatibilities typically encountered when synthetic polymers are functionalized with water-soluble molecules. Moreover, this post-assembly functionalization of a reactive thin film surface preserves the original patterning reduces the amount of required reactant, and leads to short reaction times. The demonstrated approach is expected to provide a new materials platform in applications including sensing, catalysis, pattern recognition, or microelectronics.
Properties arising from ordered periodic mesostructures are often obscured by small, randomly oriented domains and grain boundaries. Bulk macroscopic single crystals with mesoscale periodicity are ...needed to establish fundamental structure–property correlations for materials ordered at this length scale (10–100 nm). A solvent‐evaporation‐induced crystallization method providing access to large (millimeter to centimeter) single‐crystal mesostructures, specifically bicontinuous gyroids, in thick films (>100 µm) derived from block copolymers is reported. After in‐depth crystallographic characterization of single‐crystal block copolymer–preceramic nanocomposite films, the structures are converted into mesoporous ceramic monoliths, with retention of mesoscale crystallinity. When fractured, these monoliths display single‐crystal‐like cleavage along mesoscale facets. The method can prepare macroscopic bulk single crystals with other block copolymer systems, suggesting that the method is broadly applicable to block copolymer materials assembled by solvent evaporation. It is expected that such bulk single crystals will enable fundamental understanding and control of emergent mesostructure‐based properties in block‐copolymer‐directed metal, semiconductor, and superconductor materials.
A simple procedure generates single crystals from evaporation‐induced block‐copolymer self‐assembly with 1000‐fold improvement in grain size, such that macroscopic single crystals are isolated. These crystals have a complex, bicontinuous, cubic architecture, known as the double gyroid, and can be converted into freestanding porous refractory ceramic monoliths that have single‐crystal‐like optical and fracture properties.
Microcalcifications serve as diagnostic markers for breast cancer, yet their formation pathway(s) and role in cancer progression are debated due in part to a lack of relevant 3D culture models that ...allow studying the extent of cellular regulation over mineralization. Previous studies have suggested processes ranging from dystrophic mineralization associated with cell death to bone-like mineral deposition. Here, we evaluated microcalcification formation in 3D multicellular spheroids, generated from non-malignant, pre-cancer, and invasive cell lines from the MCF10A human breast tumor progression series. The spheroids with greater malignancy potential developed necrotic cores, thus recapitulating spatially distinct viable and non-viable areas known to regulate cellular behavior in tumors in vivo. The spatial distribution of the microcalcifications, as well as their compositions, were characterized using nanoCT, electron-microscopy, and X-ray spectroscopy. Apatite microcalcifications were primarily detected within the viable cell regions and their number and size increased with malignancy potential of the spheroids. Levels of alkaline phosphatase decreased with malignancy potential, whereas levels of osteopontin increased. These findings support a mineralization pathway in which cancer cells induce mineralization in a manner that is linked to their malignancy potential, but that is distinct from physiological osteogenic mineralization.
Multicolor optical super-resolution microscopy (OSRM) describes an emerging set of techniques for the specific labeling of distinct constituents of multicomponent systems with compatible optical ...probes, elucidating proximity relationships from far-field imaging of diffraction-limited features with nanometer-scale resolution. While such approaches are well established in the study of biological systems, their implementation in materials science has been considerably slower. In large part, this gradual adoption is due to the lack of appropriate OSRM probes that, e.g., by facile mixing or surface modification, enable orthogonal labeling of specific nanostructures in the condensed state, rather than in aqueous conditions as with biology. Here, OSRM probes in the form of ultrasmall (diameters <10 nm) aluminosilicate nanoparticles encapsulating different fluorescent dyes are tailored to visualize both nanodomains of polystyrene-block-poly(allyl glycidyl ether)-co-(ethylene oxide) (PS-b-P(AGE-co-EO)) diblock copolymer thin films. Careful design of nanoprobe surface chemical properties facilitates either selective compatibilization with the nonpolar PS matrix or preferential reactivity with surface allyl groups of the hydrophilic P(AGE-co-EO) minority block. Stochastic optical reconstruction microscopy (STORM) of the resulting polymer–inorganic nanocomposite thin films shows nanodomain features of the two chemically dissimilar blocks consistent with atomic force microscopy results. This work paves the way for multiplexed OSRM analysis of polymer nanocomposite bulk structures.
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