An in situ study of thermal crystallization of amorphous calcium phosphates.

The heat-induced crystallization of amorphous calcium phosphate (ACP) is an intriguing process not yet well comprehended. This is because most of the works on this topic are based on ex situ studies where the materials are characterized after the heat and cooldown cycles, thus missing transient structural changes. Here, we used time-resolved energy dispersive X-ray diffraction and infrared spectroscopy to study, for the first time, the thermal crystallization of ACP in situ. The thermal crystallization of two kinds of citrate-stabilized carbonated ACP was studied, as they are promising materials for the preparation of advanced bioceramics. The behavior of these samples was compared to that of two citrate-free ACPs, either doped or non-doped with carbonate ions. Our results evinced that several phenomena occur during ACP thermal annealing. Before crystallization, all ACP samples undergo a decrease in the short-range order process, followed by several internal reorganizations. We have assessed that differently from carbonate-free ACP, carbonated ACPs with and without citrate directly crystallize into a biomimetic poorly crystalline carbonated hydroxyapatite. Citrate-stabilized ACPs in comparison to citrate-free ACPs have a faster hydroxyapatite formation kinetics, which is due to their higher specific surface area. This work reveals the necessity and the potentialities of using in situ techniques to effectively probe complex processes such as the heat-induced crystallization of ACPs.

Optimization of In Vivo Studies by Combining Planar Dynamic and Tomographic Imaging: Workflow Evaluation on a Superparamagnetic Nanoparticles System.

Molecular imaging holds great promise in the noninvasive monitoring of several diseases with nanoparticles (NPs) being considered an efficient imaging tool for cancer, central nervous system, and heart- or bone-related diseases and for disorders of the mononuclear phagocytic system (MPS). In the present study, we used an iron-based nanoformulation, already established as an MRI/SPECT probe, as well as to load different biomolecules, to investigate its potential for nuclear planar and tomographic imaging of several target tissues following its distribution via different administration routes. Iron-doped hydroxyapatite NPs (FeHA) were radiolabeled with the single photon γ-emitting imaging agent [99mTc]TcMDP. Administration of the radioactive NPs was performed via the following four delivery methods: (1) standard intravenous (iv) tail vein, (2) iv retro-orbital injection, (3) intratracheal (it) instillation, and (4) intrarectal installation (pr). Real-time, live, fast dynamic screening studies were performed on a dedicated bench top, mouse-sized, planar SPECT system from t = 0 to 1 hour postinjection (p.i.), and consequently, tomographic SPECT/CT imaging was performed, for up to 24 hours p.i. The administration routes that have been studied provide a wide range of possible target tissues, for various diseases. Studies can be optimized following this workflow, as it is possible to quickly assess more parameters in a small number of animals (injection route, dosage, and fasting conditions). Thus, such an imaging protocol combines the strengths of both dynamic planar and tomographic imaging, and by using iron-based NPs of high biocompatibility along with the appropriate administration route, a potential diagnostic or therapeutic effect could be attained.

Nanotechnological approach and bio-inspired materials to face degenerative diseases in aging.

The aging of the world population is increasingly claimed as an alarming situation, since an ever-raising number of persons in advanced age but still physically active is expected to suffer from invalidating and degenerative diseases. The impairment of the endogenous healing potential provoked by the aging requires the development of more effective and personalized therapies, based on new biomaterials and devices able to direct the cell fate to stimulate and sustain the regrowth of damaged or diseased tissues. To obtain satisfactory results, also in cases where the cell senescence, typical of the elderly, makes the regeneration process harder and longer, the new solutions have to possess excellent ability to mimic the physiological extracellular environment and thus exert biomimetic stimuli on stem cells. To this purpose, the "biomimetic concept" is today recognized as elective to fabricate bioactive and bioresorbable devices such as hybrid osteochondral scaffolds and bioactive bone cements closely resembling the natural hard tissues and with enhanced regenerative ability. The review will illustrate some recent results related to these new biomimetic materials developed for application in different districts of the musculoskeletal system, namely bony, osteochondral and periodontal regions, and the spine. Further, it will be shown how new bioactive and superparamagnetic calcium phosphate nanoparticles can give enhanced results in cardiac regeneration and cancer therapy. Since tissue regeneration will be a major demand in the incoming decades, the high potential of biomimetic materials and devices is promising to significantly increase the healing rate and improve the clinical outcomes even in aged patients.

Calcium Phosphate Particles Coated with Humic Substances: A Potential Plant Biostimulant from Circular Economy.

Nowadays, the use of biostimulants to reduce agrochemical input is a major trend in agriculture. In this work, we report on calcium phosphate particles (CaP) recovered from the circular economy, combined with natural humic substances (HSs), to produce a plant biostimulant. CaPs were obtained by the thermal treatment of Salmo salar bones and were subsequently functionalized with HSs by soaking in a HS water solution. The obtained materials were characterized, showing that the functionalization with HS did not sort any effect on the bulk physicochemical properties of CaP, with the exception of the surface charge that was found to get more negative. Finally, the effect of the materials on nutrient uptake and translocation in the early stages of development (up to 20 days) of two model species of interest for horticulture, Valerianella locusta and Diplotaxis tenuifolia, was assessed. Both species exhibited a similar tendency to accumulate Ca and P in hypogeal tissues, but showed different reactions to the treatments in terms of translocation to the leaves. CaP and CaP-HS treatments lead to an increase of P accumulation in the leaves of D. tenuifolia, while the treatment with HS was found to increase only the concentration of Ca in V. locusta leaves. A low biostimulating effect on both plants' growth was observed, and was mainly scribed to the low concentration of HS in the tested materials. In the end, the obtained material showed promising results in virtue of its potential to elicit phosphorous uptake and foliar translocation by plants.

Mussel Shell-Derived Macroporous 3D Scaffold: Characterization and Optimization Study of a Bioceramic from the Circular Economy.

Fish industry by-products constitute an interesting platform for the extraction and recovery of valuable compounds in a circular economy approach. Among them, mussel shells could provide a calcium-rich source for the synthesis of hydroxyapatite (HA) bioceramics. In this work, HA nanoparticles have been successfully synthesized starting from mussel shells (Mytilus edulis) with a two steps process based on thermal treatment to convert CaCO3 in CaO and subsequent wet precipitation with a phosphorus source. Several parameters were studied, such as the temperature and gaseous atmosphere of the thermal treatment as well as the use of two different phosphorus-containing reagents in the wet precipitation. Data have revealed that the characteristics of the powders can be tailored, changing the conditions of the process. In particular, the use of (NH4)2HPO4 as the phosphorus source led to HA nanoparticles with a high crystallinity degree, while smaller nanoparticles with a higher surface area were obtained when H3PO4 was employed. Further, a selected HA sample was synthesized at the pilot scale; then, it was employed to fabricate porous 3D scaffolds using the direct foaming method. A highly porous scaffold with open and interconnected porosity associated with good mechanical properties (i.e., porosity in the range 87-89%, pore size in the range 50-300 µm, and a compressive strength σ = 0.51 ± 0.14 MPa) suitable for bone replacement was achieved. These results suggest that mussel shell by-products are effectively usable for the development of compounds of high added value in the biomedical field.

The Effect of the Repression of Oxidative Stress on Tenocyte Differentiation: A Preliminary Study of a Rat Cell Model Using a Novel Differential Tensile Strain Bioreactor.

Because of limitations in the current understanding of the exact pathogenesis of tendinopathy, and the lack of an optimal experimental model, effective therapy for the disease is currently unavailable. This study aims to prove that repression of oxidative stress modulates the differentiation of tendon-derived cells (TDCs) sustaining excessive tensile strains, and proposes a novel bioreactor capable of applying differential tensile strains to cultured cells simultaneously. TDCs, including tendon-derived stem cells, tenoblasts, tenocytes, and fibroblasts, were isolated from the patellar tendons of Sprague‒Dawley rats. Cyclic uniaxial stretching with 4% or 8% strain at 0.5 Hz for 8 h was applied to TDCs. TDCs subjected to 8% strain were treated with epigallocatechin gallate (EGCG), piracetam, or no medication. Genes representing non-tenocyte lineage (Pparg, Sox9, and Runx2) and type I and type III collagen were analyzed by quantitative polymerase chain reaction. The 8% strain group showed increased expression of non-tenocyte lineage genes and type III/type I collagen ratios compared with the control and 4% strain groups, and the increased expression was ameliorated with addition of EGCG and piracetam. The model developed in this work could be applied to future research on the pathophysiology of tendinopathy and development of treatment options for the disease. Repression of oxidative stress diminishes the expression of genes indicating aberrant differentiation in a rat cell model, which indicates potential therapeutic intervention of tendinopathy, the often relentlessly degenerate condition.

Interaction of Folic Acid with Nanocrystalline Apatites and Extension to Methotrexate (Antifolate) in View of Anticancer Applications.

Nanocrystalline apatites mimicking bone mineral represent a versatile platform for biomedical applications thanks to their similarity to bone apatite and the possibility to (multi)functionalize them so as to provide "à la carte" properties. One relevant domain is in particular oncology, where drug-loaded biomaterials and engineered nanosystems may be used for diagnosis, therapy, or both. In a previous contribution, we investigated the adsorption of doxorubicin onto two nanocrystalline apatite substrates, denoted HA and FeHA (superparamagnetic apatite doped with iron ions), and explored these drug-loaded systems against tumor cells. To widen their applicability in the oncology field, here we examine the interaction between the same two substrates and two other molecules: folic acid (FA), often used as cell targeting agent, and the anticancer drug methotrexate (MTX), an antifolate analogue. In a first stage, we investigated the adsorptive behavior of FA (or MTX) on both substrates, evidencing their specificities. At low concentration, typically under 100 mmol/L, adsorption onto HA was best described using the Sips isotherm model, while the formation of a calcium folate secondary salt was evidenced at high concentration by Raman spectroscopy. Adsorption onto FeHA was instead fitted to the Langmuir model. A larger adsorptive affinity was found for the FeHA substrate compared to HA; accordingly, a faster release was noticed from HA. In vitro tests carried out on human osteosarcoma cell line (SAOS-2) allowed us to evaluate the potential of these compounds in oncology. Finally, in vivo (subcutaneous) implantations in the mouse were run to ascertain the biocompatibility of the two substrates. These results should allow a better understanding of the interactions between FA/MTX and bioinspired nanocrystalline apatites in view of applications in the field of cancer.

Calcium phosphate-based nanosystems for advanced targeted nanomedicine.

Synthetic calcium phosphates (CaPs) are the most widely accepted bioceramics for the repair and reconstruction of bone tissue defects. The recent advancements in materials science have prompted a rapid progress in the preparation of CaPs with nanometric dimensions, tailored surface characteristics, and colloidal stability opening new perspectives in their use for applications not strictly related to bone. In particular, the employment of CaPs nanoparticles as carriers of therapeutic and imaging agents has recently raised great interest in nanomedicine. CaPs nanoparticles, as well as other kinds of nanoparticles, can be engineered to specifically target the site of the disease (cells or organs), thus minimizing their dispersion in the body and undesired organism-nanoparticles interactions. The most promising and efficient approach to improve their specificity is the 'active targeting', where nanoparticles are conjugated with a targeting moiety able to recognize and bind with high efficacy and selectivity to receptors that are highly expressed only in the therapeutic site. The aim of this review is to give an overview on advanced targeted nanomedicine with a focus on the most recent reports on CaP nanoparticles-based systems, specifically designed for the active targeting. The distinctive characteristics of CaP nanoparticles with respect to the other kinds of nanomaterials used in nanomedicine are also discussed.

Fe-Doping-Induced Magnetism in Nano-Hydroxyapatites.

Doping of biocompatible nanomaterials with magnetic phases is currently one of the most promising strategies for the development of advanced magnetic biomaterials. However, especially in the case of iron-doped magnetic hydroxyapatites, it is not clear if the magnetic features come merely from the magnetic phases/ions used as dopants or from complex mechanisms involving interactions at the nanoscale. Here, we report an extensive chemical-physical and magnetic investigation of three hydroxyapatite nanocrystals doped with different iron species and containing small or no amounts of maghemite as a secondary phase. The association of several investigation techniques such as X-ray absorption spectroscopy, Mössbauer, magnetometry, and TEM allowed us to determine that the unusual magnetic properties of Fe2+/3+-doped hydroxyapatites (FeHA) occur by a synergy of two different phenomena: i.e., (i) interacting superparamagnetism due to the interplay between iron-doped apatite and iron oxide nanoparticles as well as to the occurrence of dipolar interactions and (ii) interacting paramagnetism due to Fe3+ ions present in the superficial hydrated layer of the apatite nanophase and, to a lesser extent, paramagnetism due to isolated Fe3+ ions in the apatite lattice. We also show that a major player in the activation of the above phenomena is the oxidation of Fe2+ into Fe3+, as induced by the synthesis process, and their consequent specific positioning in the FeHA structure.

Biomimetic mineralization of recombinant collagen type I derived protein to obtain hybrid matrices for bone regeneration.

Understanding the mineralization mechanism of synthetic protein has recently aroused great interest especially in the development of advanced materials for bone regeneration. Herein, we propose the synthesis of composite materials through the mineralization of a recombinant collagen type I derived protein (RCP) enriched with RGD sequences in the presence of magnesium ions (Mg) to closer mimic bone composition. The role of both RCP and Mg ions in controlling the precipitation of the mineral phase is in depth evaluated. TEM and X-ray powder diffraction reveal the crystallization of nanocrystalline apatite (Ap) in all the evaluated conditions. However, Raman spectra point out also the precipitation of amorphous calcium phosphate (ACP). This amorphous phase is more evident when RCP and Mg are at work, indicating the synergistic role of both in stabilizing the amorphous precursor. In addition, hybrid matrices are prepared to tentatively address their effectiveness as scaffolds for bone tissue engineering. SEM and AFM imaging show an homogeneous mineral distribution on the RCP matrix mineralized in presence of Mg, which provides a surface roughness similar to that found in bone. Preliminary in vitro tests with pre-osteoblast cell line show good cell-material interaction on the matrices prepared in the presence of Mg. To the best of our knowledge this work represents the first attempt to mineralize recombinant collagen type I derived protein proving the simultaneous effect of the organic phase (RCP) and Mg on ACP stabilization. This study opens the possibility to engineer, through biomineralization process, advanced hybrid matrices for bone regeneration.

pH-responsive collagen fibrillogenesis in confined droplets induced by vapour diffusion.

A novel methodology for the assembly of collagen fibrils in microliter drops is proposed. It consists in the gradual increase of pH by means of vapour diffusion coming from the decomposition of NH4HCO3 solutions. The pH increase rate as well as the final steady pH of solutions containing collagen can be adjusted by varying the concentration of NH4HCO3. Both parameters are of predominant importance in collagen fibrillogenesis. The effect of these parameters on the kinetic of the fibrillogenesis process and on the fibrils morphology was studied. We found that both the kinetic and the morphology are mainly driven by electrostatic interactions. A gradual increase of pH slows down the formation of collagen fibres and favours the lateral interaction between fibrils producing broader fibres. On the other hand, a rapid increase of pH reduces the lateral electrostatic interactions favouring the formation of thinner fibres. The formation of the D-band periodicity is also a pH-dependent process that occurs after fibrillogenesis when the most stable state of fibres formation has been reached.

Growth on poly(L-lactic acid) porous scaffold preserves CD73 and CD90 immunophenotype markers of rat bone marrow mesenchymal stromal cells.

Few data are available on the effect of biomaterials on surface antigens of mammalian bone marrow-derived, adult mesenchymal stromal cells (MSCs). Since poly(L-lactic acid) or PLLA is largely used in tissue engineering of human bones, and we are developing a reverse engineering program to prototype with biomaterials the vascular architecture of bones for their bioartificial reconstruction, both in humans and animal models, we have studied the effect of porous, flat and smooth PLLA scaffolds on the immunophenotype of in vitro grown, rat MSCs in the absence of any coating, co-polymeric enrichment, and differentiation stimuli. Similar to controls on plastic, we show that our PLLA scaffold does not modify the distribution of some surface markers in rat MSCs. In particular, the maintained expression of CD73 and CD90 on two different subpopulations (small and large cells) is consistent with their adhesion to the PLLA scaffold through specialized appendages, and to their prominent content in actin. In addition, our PLLA scaffold favours retention of the intermediate filament desmin, believed a putative marker of undifferentiated state. Finally, it preserves all rat MSCs morphotypes, and allows for their survival, adhesion to the substrate, and replication. Remarkably, a subpopulation of rat MSCs grown on our PLLA scaffold exhibited formation of membrane protrusions of uncertain significance, although in a size range and morphology compatible with either motility blebs or shedding vesicles. In summary, our PLLA scaffold has no detrimental effect on a number of features of rat MSCs, primarily the expression of CD73 and CD90.

Natural, biphasic calcium phosphate from fish bones for enamel remineralization and dentin tubules occlusion.

OBJECTIVES: A calcium phosphate extracted from fish bones (CaP-N) was evaluated for enamel remineralization and dentinal tubules occlusion. METHODS: CaP-N was characterized by assessing morphology by SEM, crystallinity by PXRD, and composition by ICP-OES. CaP-N morphology, crystallinity, ion release, and pH changes over time in neutral and acidic solutions were studied. CaP-N was then tested to assess remineralization and dentinal tubules occlusion on demineralized human enamel and dentin specimens (n = 6). Synthetic calcium phosphate in form of stoichiometric hydroxyapatite nanoparticles (CaP-S) and tap water were positive and negative controls, respectively. After treatment (brush every 12 h for 5d and storage in Dulbecco's modified PBS), specimens' morphology and surface composition were assessed (by SEM-EDS), while the viscoelastic behavior was evaluated with microindentation and DMA. RESULTS: CaP-N consisted of rounded microparticles (200 nm - 1 µm) composed of 33 wt% hydroxyapatite and 67 wt% ß-tricalcium phosphate. In acidic solution, CaP-N released calcium and phosphate ions thanks to the preferential ß-tricalcium phosphate phase dissolution. Enamel remineralization was induced by CaP-N comparably to CaP-S, while CaP-N exhibited a superior dentinal tubule occlusion than CaP-S, forming mineral plugs and depositing new nanoparticles onto demineralized collagen. This behavior was attributed to its bigger particle size and increased solubility. DMA depth profiling and SEM showed an excellent interaction between the newly formed mineralized structures and the pristine tissue, particularly at the exposed collagen fibrils. SIGNIFICANCE: CaP-N demonstrated very good remineralizing and occlusive activity in vitro, comparable to CaP-S, thus could be a promising circular economy alternative therapeutic agent for dentistry.

Bioinspired oriented calcium phosphate nanocrystal arrays with bactericidal and osteogenic properties.

The global diffusion of antibiotic resistance poses a severe threat to public health. Addressing antibiotic-resistant infections requires innovative approaches, such as antibacterial nanostructured surfaces (ANSs). These surfaces, featuring ordered arrays of nanostructures, exhibit the ability to kill bacteria upon contact. However, most currently developed ANSs utilize bioinert materials, lacking bioactivity crucial for promoting tissue regeneration, particularly in the context of bone infections. This study introduces ANSs composed of bioactive calcium phosphate nanocrystals. Two distinct ANSs were created through a biomineralization-inspired growth of amorphous calcium phosphate (ACP) precursors. The ANSs demonstrated efficient antibacterial properties against both Gram-negative (P. aeruginosa) and Gram-positive (S. aureus) antibiotic resistant bacteria, with up to 75 % mortality in adhered bacteria after only 4 h of contact. Notably, the ANS featuring thinner and less oriented nano-needles exhibited superior efficacy attributed to simultaneous membrane rupturing and oxidative stress induction. Moreover, the ANSs facilitate the proliferation of mammalian cells, enhancing adhesion, spreading, and reducing oxidative stress. The ANSs displayed also significant bioactivity towards human mesenchymal stem cells, promoting colonization and inducing osteogenic differentiation. Specifically, the ANS with thicker and more ordered nano-needles demonstrated heightened effects. In conclusion, ANSs introduced in this work have the potential to serve as foundation for developing bone graft materials capable of eradicate site infections while concurrently stimulating bone regeneration. STATEMENT OF SIGNIFICANCE: Nanostructured surfaces with antibacterial properties through a mechano-bactericidal mechanism have shown significant potential in fighting antibiotic resistance. However, these surfaces have not been fabricated with bioactive materials necessary for developing devices that are both antibacterial and able to stimulate tissue regeneration. This study demonstrates the feasibility of creating nanostructured surfaces of ordered calcium phosphate nano-needles through a biomineralization-inspired growth. These surfaces exhibit dual functionality, serving as effective bactericidal agents against Gram-negative and Gram-positive antibiotic-resistant bacteria while also promoting the proliferation of mammalian cells and inducing osteogenic differentiation of human mesenchymal stem cells. Consequently, this approach holds promise in the context of bone infections, introducing innovative nanostructured surfaces that could be utilized in the development of antimicrobial and osteogenic grafts.

Stearate-Coated Biogenic Calcium Carbonate from Waste Seashells: A Sustainable Plastic Filler.

Waste seashells from aquaculture are a massive source of biogenic calcium carbonate (bCC) that can be a potential substitute for ground calcium carbonate and precipitated calcium carbonate. These last materials find several applications in industry after a surface coating with hydrophobic molecules, with stearate as the most used. Here, we investigate for the first time the capability of aqueous stearate dispersions to coat bCC powders from seashells of market-relevant mollusc aquaculture species, namely the oyster Crassostrea gigas, the scallop Pecten jacobaeus, and the clam Chamelea gallina. The chemical-physical features of bCC were extensively characterized by different analytical techniques. The results of stearate adsorption experiments showed that the oyster shell powder, which is the bCC with a higher content of the organic matrix, showed the highest adsorption capability (about 23 wt % compared to 10 wt % of geogenic calcite). These results agree with the mechanism proposed in the literature in which stearate adsorption mainly involves the formation of calcium stearate micelles in the dispersion before the physical adsorption. The coated bCC from oyster shells was also tested as fillers in an ethylene vinyl acetate compound used for the preparation of shoe soles. The obtained compound showed better mechanical performance than the one prepared using ground calcium. In conclusion, we can state that bCC can replace ground and precipitated calcium carbonate and has a higher stearate adsorbing capability. Moreover, they represent an environmentally friendly and sustainable source of calcium carbonate that organisms produce by high biological control over composition, polymorphism, and crystal texture. These features can be exploited for applications in fields where calcium carbonate with selected features is required.

Lung-to-Heart Nano-in-Micro Peptide Promotes Cardiac Recovery in a Pig Model of Chronic Heart Failure.

BACKGROUND: The lack of disease-modifying drugs is one of the major unmet needs in patients with heart failure (HF). Peptides are highly selective molecules with the potential to act directly on cardiomyocytes. However, a strategy for effective delivery of therapeutics to the heart is lacking. OBJECTIVES: In this study, the authors sought to assess tolerability and efficacy of an inhalable lung-to-heart nano-in-micro technology (LungToHeartNIM) for cardiac-specific targeting of a mimetic peptide (MP), a first-in-class for modulating impaired L-type calcium channel (LTCC) trafficking, in a clinically relevant porcine model of HF. METHODS: Heart failure with reduced ejection fraction (HFrEF) was induced in Göttingen minipigs by means of tachypacing over 6 weeks. In a setting of overt HFrEF (left ventricular ejection fraction [LVEF] 30% ± 8%), animals were randomized and treatment was started after 4 weeks of tachypacing. HFrEF animals inhaled either a dry powder composed of mannitol-based microparticles embedding biocompatible MP-loaded calcium phosphate nanoparticles (dpCaP-MP) or the LungToHeartNIM only (dpCaP without MP). Efficacy was evaluated with the use of echocardiography, invasive hemodynamics, and biomarker assessment. RESULTS: DpCaP-MP inhalation restored systolic function, as shown by an absolute LVEF increase over the treatment period of 17% ± 6%, while reversing cardiac remodeling and reducing pulmonary congestion. The effect was recapitulated ex vivo in cardiac myofibrils from treated HF animals. The treatment was well tolerated, and no adverse events occurred. CONCLUSIONS: The overall tolerability of LungToHeartNIM along with the beneficial effects of the LTCC modulator point toward a game-changing treatment for HFrEF patients, also demonstrating the effective delivery of a therapeutic peptide to the diseased heart.

Cell surface receptor targeted biomimetic apatite nanocrystals for cancer therapy.

Nanosized drug carriers functionalized with moieties specifically targeting tumor cells are promising tools in cancer therapy, due to their ability to circulate in the bloodstream for longer periods and their selectivity for tumor cells, enabling the sparing of healthy tissues. Because of its biocompatibility, high bioresorbability, and responsiveness to pH changes, synthetic biomimetic nanocrystalline apatites are used as nanocarriers to produce multifunctional nanoparticles, by coupling them with the chemotherapeutic drug doxorubicin (DOXO) and the DO-24 monoclonal antibody (mAb) directed against the Met/Hepatocyte Growth Factor receptor (Met/HGFR), which is over-expressed on different types of carcinomas and thus represents a useful tumor target. The chemical-physical features of the nanoparticles are fully investigated and their interaction with cells expressing (GTL-16 gastric carcinoma line) or not expressing (NIH-3T3 fibroblasts) the Met/HGFR is analyzed. Functionalized nanoparticles specifically bind to and are internalized in cells expressing the receptor (GTL-16) but not in the ones that do not express it (NIH-3T3). Moreover they discharge DOXO in the targeted GTL-16 cells that reach the nucleus and display cytotoxicity as assessed in an MTT assay. Two different types of ternary nanoparticles are prepared, differing for the sequence of the functionalization steps (adsorption of DOXO first and then mAb or vice versa), and it is found that the ones in which mAb is adsorbed first are more efficient under all the examined aspects (binding, internalization, cytotoxicity), possibly because of a better mAb orientation on the nanoparticle surface. These multifunctional nanoparticles could thus be useful instruments for targeted local or systemic drug delivery, allowing a reduction in the therapeutic dose of the drug and thus adverse side effects. Moreover, this work opens new perspectives in the use of nanocrystalline apatites as a new platform for theranostic applications in nanomedicine.

pH-responsive delivery of doxorubicin from citrate-apatite nanocrystals with tailored carbonate content.

In this work, the efficiency of bioinspired citrate-functionalized nanocrystalline apatites as nanocarriers for delivery of doxorubicin (DOXO) has been assessed. The nanoparticles were synthesized by thermal decomplexing of metastable calcium/citrate/phosphate solutions both in the absence (Ap) and in the presence (cAp) of carbonate ions. The presence of citrate and carbonate ions in the solution allowed us to tailor the size, shape, carbonate content, and surface chemistry of the nanoparticles. The drug-loading efficiency of the two types of apatite was evaluated by means of the adsorption isotherms, which were found to fit a Langmuir-Freundlich behavior. A model describing the interaction between apatite surface and DOXO is proposed from adsorption isotherms and ζ-potential measurements. DOXO is adsorbed as a dimer by means of a positively charged amino group that electrostatically interacts with negatively charged surface groups of nanoparticles. The drug-release profiles were explored at pHs 7.4 and 5.0, mimicking the physiological pH in the blood circulation and the more acidic pH in the endosome-lysosome intracellular compartment, respectively. After 7 days at pH 7.4, cAp-DOXO released around 42% less drug than Ap-DOXO. However, at acidic pH, both nanoassemblies released similar amounts of DOXO. In vitro assays analyzed by confocal microscopy showed that both drug-loaded apatites were internalized within GTL-16 human carcinoma cells and could release DOXO, which accumulated in the nucleus in short times and exerted cytotoxic activity with the same efficiency. cAp are thus expected to be a more promising nanocarrier for experiments in vivo, in situations where intravenous injection of nanoparticles are required to reach the targeted tumor, after circulating in the bloodstream.

Calcium phosphates from fish bones in sunscreen: An LCA and toxicity study of an emerging material for circular economy.

The use of sustainable and natural materials is an ever-increasing trend in cosmetic. Natural calcium phosphate (CaP-N) from food by-products and especially from fisheries (i.e., bones), has been suggested as a sustainable option to chemicals commonly used in cosmetic products, in particular to UV-filters in sunscreens. However, the environmental benefits and impacts of its production and use are still uncertain as they have never been quantified. In this paper, we report on toxicological characterization of CaP-N produced from incineration of fish meal in a pilot scale plant. Furthermore, we quantified the environmental burdens linked to the partial substitution of UV-filters by CaP-N through the life cycle assessment (LCA) comparing CaP-N with zinc oxide nanoparticles (ZnO NPs) as alternative option. CaP-N consists in a biphasic mixture 53:47 of hydroxyapatite:ß-tricalcium phosphate, and is made of round particles with a diameter in the range of a few microns. Toxicity tests on 4 aquatic species (Dunaliella tertiolecta, Tigriopus fulvus, Corophium insidiosum and Gammarus aequicauda) revealed that CaP-N does not produce any adverse effect, all the species showing EC/LC50 values higher than 100 mg L-1. Moreover, during the 96 h acute toxicity test on C. insidiosum, which is a tube-building species, the specimens built their tubes with the available CaP-N, further attesting the non-toxicity of the material. The LCA study showed that the environmental performance of CaP-N is better than that of ZnO NPs for 11 out of 16 impact categories analysed in this study, especially for the categories Ecotoxicity and Eutrophication of freshwaters (an order of magnitude lower), and with the exception of fossil resources for which CaP-N has a significantly higher impact than ZnO NPs (+140 %). Concluding, our study demonstrates that the replacement of ZnO NPs with CaP-N thermally extracted from fish bones in cosmetic products can increase their safety and sustainability.