Hierarchy of Hybrid Materials-The Place of Inorganics-in-Organics in it, Their Composition and Applications

Thin Films Based on Cobalt Phthalocyanine:C60 Fullerene:ZnO Hybrid Nanocomposite Obtained by Laser Evaporation

Matrix-assisted pulsed laser evaporation (MAPLE) was used to deposit hybrid nanocomposite thin films based on cobalt phthalocyanine (CoPc), C60 fullerene and ZnO nanoparticles. The inorganic nanoparticles, with a size of about 20 nm, having the structural and optical properties characteristic of ZnO, were chemically synthesized by a simple precipitation method. Furthermore, ZnO nanoparticles were dispersed in a dimethyl sulfoxide solution in which CoPc and C60 had been dissolved, ready for the freezing MAPLE target. The effect of the concentration of ZnO nanoparticles on the structural, morphological, optical and electrical properties of the CoPc:C60:ZnO hybrid nanocomposite layers deposited by MAPLE was evaluated. The infrared spectra of the hybrid nanocomposite films confirm that the CoPc and C60 preserve their chemical structure during the laser deposition process. The CoPc optical signature is recognized in the ultraviolet-visible (UV-Vis) spectra of the obtained layers, these being dominated by the absorption bands associated to this organic compound while the ZnO optical fingerprint is identified in the photoluminescence spectra of the prepared layers, these disclosing the emission bands linked to this inorganic semiconductor. The hybrid nanocomposite layers exhibit globular morphology, which is typical for the thin films deposited by MAPLE. Current-voltage (J-V) characteristics of the structures developed on CoPc:C60:ZnO layers reveal that the addition of an appropriate amount of ZnO nanoparticles in the CoPc:C60 mixture leads to a more efficient charge transfer between the organic and inorganic components. Due to their photovoltaic effect, structures featuring such hybrid nanocomposite thin films deposited by MAPLE can have potential applications in the field of photovoltaic devices.

Freezing-Induced Loading of TiO2 into Porous Vaterite Microparticles: Preparation of CaCO3/TiO2 Composites as Templates To Assemble UV-Responsive Microcapsules for Wastewater Treatment

The photocatalytic degradation of organic molecules is one of the effective ways for water purification. At this point, photocatalytic microreactor systems seem to be promising to enhance the versatility of the photoassisted degradation approach. Herein, we propose photoresponsive microcapsules prepared via layer-by-layer assembly of polyelectrolytes on the novel CaCO₃/TiO₂ composite template cores. The preparation of CaCO₃/TiO₂ composite particles is challenging because of the poor compatibility of TiO₂ and CaCO₃ in an aqueous medium. To prepare stable CaCO₃/TiO₂ composites, TiO₂ nanoparticles were loaded into mesoporous CaCO₃ microparticles with a freezing-induced loading technique. The inclusion of TiO₂ nanoparticles into CaCO₃ templates was evaluated with scanning electron microscopy and elemental analysis with respect to their type, concentration, and number of loading iterations. Upon polyelectrolyte shell assembly, the CaCO₃ matrix was dissolved, resulting in microreactor capsules loaded with TiO₂ nanoparticles. The photoresponsive properties of the resulted capsules were tested by photoinduced degradation of the low-molecule dye rhodamine B in aqueous solution and fluorescently labeled polymer molecules absorbed on the capsule surface under UV light. The exposure of the capsules to UV light resulted in a pronounced degradation of rhodamine B in capsule microvolume and fluorescent molecules on the capsule surface. Finally, the versatility of preparation of multifunctional photocatalytic and magnetically responsive capsules was demonstrated by iterative freezing-induced loading of TiO₂ and magnetite Fe₃O₄ nanoparticles into CaCO₃ templates.

Improvement of oxidation resistance of polymer-based nanocomposites through sonication of carbonaceous nanoparticles

The work aim is focused on two different aspects: first, the investigation of the effect of extended ultra-sound-assisted treatment (us) of carbonaceous nanoparticles, such as carbon nanotubes (CNTs) and carbon black (CB), on their radical scavenging activity, and second, the investigation of the oxidative resistance of polymer-based nanocomposites, containing us-treated CNTs and CB. Particularly, the CNTs and CB have been subjected to us sonication for different time intervals and the performed analysis reveals that both kinds of nanoparticles show decreased average hydrodynamic diameters and large content of surface defects. Really, the increased content of CNTs and CB defects, achieved during the sonication time, leads to an increased reactivity toward 1,1-diphenyl-2-pycryl (DPPH) radicals and an enhanced anti-oxidant activity toward macro-radicals, coming from the photo-degradation of the host polymer matrix. The studies of photo-oxidative behavior of the nanocomposites, based on Ultra High Molecular Weight (UHMWPE), reveal that the us treatment of the nanoparticles has a benefic effect on the oxidative resistance of the nanocomposites, especially at long exposure times. Overall, the ultra-sound-assisted treatment can be considered twofold powerful tool: (i) for disruption of the nanoparticles aggregations, and (ii) for capitalization of surface defects, amplifying and tuning in a controlled way the radical scavenging activity of the carbonaceous nanoparticles.

Classification of analytics, sensorics, and bioanalytics with polyelectrolyte multilayer capsules

Polyelectrolyte multilayer (PEM) capsules, constructed by LbL (layer-by-layer)-adsorbing polymers on sacrificial templates, have become important carriers due to multifunctionality of materials adsorbed on their surface or encapsulated into their interior. They have been also been used broadly used as analytical tools. Chronologically and traditionally, chemical analytics has been developed first, which has long been synonymous with all analytics. But it is not the only development. To the best of our knowledge, a summary of all advances including their classification is not available to date. Here, we classify analytics, sensorics, and biosensorics functionalities implemented with polyelectrolyte multilayer capsules and coated particles according to the respective stimuli and application areas. In this classification, three distinct categories are identified: (I) chemical analytics (pH; K⁺, Na⁺, and Pb²⁺ ion; oxygen; and hydrogen peroxide sensors and chemical sensing with surface-enhanced Raman scattering (SERS)); (II) physical sensorics (temperature, mechanical properties and forces, and osmotic pressure); and (III) biosensorics and bioanalytics (fluorescence, glucose, urea, and protease biosensing and theranostics). In addition to this classification, we discuss also principles of detection using the above-mentioned stimuli. These application areas are expected to grow further, but the classification provided here should help (a) to realize the wealth of already available analytical and bioanalytical tools developed with capsules using inputs of chemical, physical, and biological stimuli and (b) to position future developments in their respective fields according to employed stimuli and application areas. Graphical abstract.

Fabrication and characterization of dextran/nanocrystalline β-tricalcium phosphate nanocomposite hydrogel scaffolds

Design of bioactive three-dimensional scaffolds to support bone tissue repair and regeneration become a key area of research in tissue engineering. Herein, porous hybrid hydrogels composed of dextran incorporated with nanocrystalline β-tricalcium phosphate (β-TCP) particles were tailor made as scaffolds for bone tissue engineering. β-TCP was successfully introduced within the dextran networks crosslinked through intermolecular ionic interactions and hydrogen bonding confirmed by FTIR spectroscopy. The effect of β-TCP content on equilibrium water uptake and swelling kinetics of composite hydrogels was investigated. It was found that the homogeneous distribution of β-TCP nanoparticles through the hydrogel matrix contributes to higher porosity and swelling capacity. In depth swelling measurements revealed that while in the early stage of swelling, water diffusion follows the Fick's law, for longer time swelling behavior of hydrogels undergo the second order kinetics. XRD measurements represented the formation of apatite layer on the surface of nanocomposite hydrogels after immersion in the SBF solution, which implies their bioactivity. Cell culture assays confirmed biocompatibility of the developed hybrid hydrogels in vitro. The obtained results converge to offer dextran/β-TCP nanocomposite hydrogels as promising scaffolds for bone regeneration applications.

Polycaprolactone-Based, Porous CaCO3 and Ag Nanoparticle Modified Scaffolds as a SERS Platform With Molecule-Specific Adsorption

Surface-enhanced Raman scattering (SERS) is a high-performance technique allowing detection of extremely low concentrations of analytes. For such applications, fibrous polymeric matrices decorated with plasmonic metal nanostructures can be used as flexible SERS substrates for analysis of analytes in many application. In this study, a three-dimensional SERS substrate consisting of a CaCO₃-mineralized electrospun (ES) polycaprolactone (PCL) fibrous matrix decorated with silver (Ag) nanoparticles is developed. Such modification of the fibrous substrate allows achieving a significant increase of the SERS signal amplification. Functionalization of fibers by porous CaCO₃ (vaterite) and Ag nanoparticles provides an effective approach of selective adsorption of biomolecules and their precise detection by SERS. This new SERS substrate represents a promising biosensor platform with selectivity to low and high molecular weight molecules.

Morphological transformation of ultrasonically obtained nanofibers during living self-assembly

The nanofibers are obtained by ionic self-assembly and living self-assembly.

Therapeutic potential of polypeptide-based conjugates: Rational design and analytical tools that can boost clinical translation

The clinical success of polypeptides as polymeric drugs, covered by the umbrella term "polymer therapeutics," combined with related scientific and technological breakthroughs, explain their exponential growth in the development of polypeptide-drug conjugates as therapeutic agents. A deeper understanding of the biology at relevant pathological sites and the critical biological barriers faced, combined with advances regarding controlled polymerization techniques, material bioresponsiveness, analytical methods, and scale up-manufacture processes, have fostered the development of these nature-mimicking entities. Now, engineered polypeptides have the potential to combat current challenges in the advanced drug delivery field. In this review, we will discuss examples of polypeptide-drug conjugates as single or combination therapies in both preclinical and clinical studies as therapeutics and molecular imaging tools. Importantly, we will critically discuss relevant examples to highlight those parameters relevant to their rational design, such as linking chemistry, the analytical strategies employed, and their physicochemical and biological characterization, that will foster their rapid clinical translation.

Inter-protein interactions govern protein loading into porous vaterite CaCO3 crystals

Loading of therapeutic proteins into mesoporous vaterite crystals is driven by inter-protein interactions in bulk solution and inside the crystals.

Naturally derived nano- and micro-drug delivery vehicles: halloysite, vaterite and nanocellulose

We discuss prospects for halloysite nanotubes, vaterite crystals and nanocellulose to enter the market of biomaterials for drug delivery and tissue engineering, and their potential for economically viable production from abundant natural sources.

Encapsulation of a Neutral Molecule into a Cationic Clay Material: Structural Insight and Cytotoxicity of Resveratrol/Layered Double Hydroxide/BSA Nanocomposites

Resveratrol (RES) is a stilbenoid polyphenol with interesting antitumor activity compromised by its poor solubility and bioavailability; thus, new approaches are necessary to improve its therapeutic effectiveness. In the present study, bovine serum albumin coated layered double hydroxide (LDH-BSA) was employed to encapsulate RES in order to overcome the above-mentioned usage limits. To evaluate the feasibility of neutral RES complexation with cationic LDH, we carried out molecular dynamics simulation in order to predict its structure and stability. In the supramolecular complex formed with LDH, RES disposes itself in the interlamellar region of LDH where it is stabilized by intermolecular interactions. The physico-chemical characteristics of the resulting nanocomplexes were studied by X-ray powder diffraction, transmission electron microscopy, and attenuated total reflection Fourier transform infrared spectroscopy. The encapsulation efficiency and drug release studies were also performed. The combined experimental and computational approach were highly effective in giving insight into the interaction mode of the neutral RES with the charged LDH. Finally, the nanohybrid's anticancer ability was evaluated in human lung cancer cell line (A549) resulting in higher activity with respect to bare RES. Overall, the results showed that the nanocomposites are suitable for biomedical applications as delivery agents of RES.

Absorbable nanocomposites composed of mesoporous bioglass nanoparticles and polyelectrolyte complexes for surgical hemorrhage control

Absorbable polyelectrolyte complexes-based hemostats are promising for controlling hemorrhage in iatrogenic injuries during surgery, whereas their hemostatic efficacy and other performances require further improvement for clinical application. Herein, spherical mesoporous bioglass nanoparticles (mBGN) were fabricated, and mBGN-polyelectrolyte complexes (composed of carboxymethyl starch and chitosan oligosaccharide) nanocomposites (BGN/PEC) with different mBGN contents were prepared via in situ coprecipitation followed by lyophilization. The effect of various mBGN content (10 and 20 wt%) on morphology, zeta potential, water absorption, degradation behavior and ion release were systematically evaluated. The in vitro degradability was dramatically promoted and a more neutral environment was achieved with the incorporation of mBGN, which is preferable for surgical applications. The in vitro coagulation test with whole blood demonstrated that the incorporation of mBGN facilitated blood clotting process. The plasma coagulation evaluation indicated that BGN/PEC had increased capability to accelerate coagulation cascade via the intrinsic pathway than that of the PEC, while have inapparent influence on the extrinsic and common pathway. The in vivo hemostatic evaluation in a rabbit hepatic hemorrhage model revealed that BGN/PEC with 10 wt% mBGN (10BGN/PEC) treatment group had the lowest blood loss, although its hemostatic time is close to that of 20BGN/PEC treatment group. The cytocompatibility evaluation with MC3T3-L1 fibroblasts indicated that 10BGN/PEC induced a ~25% increase of cell viability compared to the PEC at days 4 and 7, indicating improved biocompatibility. These findings support the promising application of absorbable BGN/PEC with optimized mBGN content as internal hemostats and present a platform for further development of PEC-based hemostats.

Enhanced osseointegration of double network hydrogels via calcium polyphosphate incorporation for bone regeneration

To overcome the low mechanical strength and difficult bonding of hydrogels to bones which are the major limitations of hydrogels used in bone-regeneration, a new type of calcium polyphosphate incorporated into bioinspired alginate/polyacrylic acid (CPP/PAA-Alg) hybrid double network (DN) hydrogel with both high strength and enhanced osseointergration was prepared by a two-step polymerization with alginate and polyacrylic acid for bone regeneration. The morphology, mechanical properties, swelling, biocompatibility, osseointegration and osteogenic ability of this CPP/PAA-Alg DN hydrogel were investigated. The results show that CPP/PAA-Alg DN hydrogel with highly porous microstructure possesses high water absorption capacity and highly strength properties which meet the requirements of bone repairing. The results of in vitro studies revealed that the CPP/PAA-Alg DN hydrogels can support the spread of cells and promote the cell proliferation. Animal studies demonstrated that the CPP incorporated would enhance the osseointegration of DN hydrogel with host bone at an early stage after implantation to accelerate the regeneration of bone. This research may provide a new way to develop biocompatible biomaterials with high mechanical strength and good osseointegration to meet the needs of bone regeneration.

Polysaccharide-Hydrophobic Nanoparticle Hybrid Nanoclusters for Enhanced Performance in Magnetic Resonance/Photoacoustic Imaging

Polysaccharide-nanoparticle (NP) hybrid nanoclusters have great potential to revitalize diverse bioapplications; however, fabricating polysaccharide-based hybrid nanoclusters composed of high-quality NPs generated in the organic phase remains a challenge. Here, using calcium alginate as a polysaccharide/tetramethylammonium hydroxide (TMAOH) combination, we report a novel approach to the design of alginate-hydrophobic magnetic-plasmonic core-shell (MPCS) NP hybrid nanoclusters (A-MPCS HNCs). Furthermore, we observe the dependence of the formation of A-MPCS HNCs on the TMAOH concentration. The enhanced performance in both magnetic resonance r₂ relaxivity and photoacoustic (PA) signals and the biocompatibility/bioactivity as well as the in vivo performance of A-MPCS HNCs shows them to be a promising magnetic resonance/photoacoustic dual-mode imaging agent. Our strategy could open doors to the use of other precious high-quality nanomaterials created in the organic phase via well-established synthetic chemistry in the design of alginate-hydrophobic nanomaterial hybrid nanoclusters, giving rise to novel and multifarious bioapplications.

Organic-inorganic nanoflowers: from design strategy to biomedical applications

Organic-inorganic hybrid nanoflowers (NF) with sizes or features on a nanoscale are a class of flower-shaped nanomaterials self-assembled from metal ions and organic components. Here, to be more specific, the organic components mainly refer to biomolecules ranging from proteins, peptides, and amino acids to DNA/RNA. Beyond their pleasing aesthetics, their unique properties and integrated functions have attracted widespread interest and made them promising candidates in the application of biomedical areas. Great efforts have been made to design and synthesize versatile functional hybrid nanoflowers. In this review, we begin with the clarification of versatile recently reported hybrid nanoflowers according to the types of metal ions and biomolecules employed. To highlight the design of organic-inorganic hybrid nanoflowers, their synthetic methods and mechanisms, structural and biological characteristics are discussed. After that, the state-of-the-art applications of hybrid nanoflowers in biomedical fields including biosensing, biocatalysis, and cancer therapy are demonstrated. In the end, we discuss the prospects of organic-inorganic hybrid nanoflowers and highlight the challenges and opportunities for future research.

Hybrids of Polymeric Capsules, Lipids, and Nanoparticles: Thermodynamics and Temperature Rise at the Nanoscale and Emerging Applications

The importance of thermodynamics does not need to be emphasized. Indeed, elevated temperature processes govern not only industrial scale production but also self-assembly, chemical reaction, interaction between molecules, etc. Not surprisingly, biological processes typically take place at a specific temperature. Here, we look at possibilities to raise the localized temperature by a laser around noble-metal nanoparticles incorporated into shells of layer-by-layer polyelectrolyte microcapsules-freely suspended delivery vehicles in an aqueous solution, developed in the Department of Interfaces, Max Planck Institute of Colloids and Interfaces, headed by Helmuth Möhwald. Understanding the mechanisms of localized temperature rise is essential, that is why we analyze the influence of incident intensity, nanoparticle size, their distribution and aggregation state, as well as thermodynamics at the nanoscale. This leads us to scrutinize "global" (used for thermal encapsulation) versus "local" (used for release of encapsulated materials) temperature rise. Similar analysis is extended to planar polymeric coatings, the lipid membrane system of vesicles and cells, on which nanoparticles are adsorbed. Insights are provided into the mechanisms of physicochemical and biological effects, the nature of which has always been profoundly, interactively, and engagingly discussed in the Department of Interfaces. This analysis is combined with recent developments providing outlook and highlighting a broad range of emerging applications.

Boosting mesenchymal stem cells regenerative activities on biopolymers-calcium phosphate functionalized collagen membrane

The regeneration of bone-soft tissue interface, using functional membranes, remains challenging and can be promoted by improving mesenchymal stem cells (MSCs) paracrine function. Herein, a collagen membrane, used as guided bone regeneration membrane, was functionalized by calcium phosphate, chitosan and hyaluronic acid hybrid coating by simultaneous spray of interacting species process. Composed of brushite, octacalcium phosphate and hydroxyapatite, the hybrid coating increased the membrane stiffness by 50%. After 7 days of MSCs culture on the hybrid coated polymeric membrane, biological studies were marked by a lack of osteoblastic commitment. However, MSCs showed an enhanced proliferation along with the secretion of cytokines and growth factors that could block bone resorption and favour endothelial cell recruitment without exacerbating polynuclear neutrophils infiltration. These data shed light on the great potential of inorganic/organic coated collagen membranes as an alternative bioactive factor-like platform to improve MSCs regenerative capacity, in particular to support bone tissue vascularization and to modulate inflammatory infiltrates.

Porous Alginate Scaffolds Assembled Using Vaterite CaCO3 Crystals

Formulation of multifunctional biopolymer-based scaffolds is one of the major focuses in modern tissue engineering and regenerative medicine. Besides proper mechanical/chemical properties, an ideal scaffold should: (i) possess a well-tuned porous internal structure for cell seeding/growth and (ii) host bioactive molecules to be protected against biodegradation and presented to cells when required. Alginate hydrogels were extensively developed to serve as scaffolds, and recent advances in the hydrogel formulation demonstrate their applicability as "ideal" soft scaffolds. This review focuses on advanced porous alginate scaffolds (PAS) fabricated using hard templating on vaterite CaCO3 crystals. These novel tailor-made soft structures can be prepared at physiologically relevant conditions offering a high level of control over their internal structure and high performance for loading/release of bioactive macromolecules. The novel approach to assemble PAS is compared with traditional methods used for fabrication of porous alginate hydrogels. Finally, future perspectives and applications of PAS for advanced cell culture, tissue engineering, and drug testing are discussed.

Piezoelectric 3-D Fibrous Poly(3-hydroxybutyrate)-Based Scaffolds Ultrasound-Mineralized with Calcium Carbonate for Bone Tissue Engineering: Inorganic Phase Formation, Osteoblast Cell Adhesion, and Proliferation

Elaboration of novel biocomposites providing simultaneously both biodegradability and stimulated bone tissue repair is essential for regenerative medicine. In particular, piezoelectric biocomposites are attractive because of a possibility to electrically stimulate cell response. In the present study, novel CaCO₃-mineralized piezoelectric biodegradable scaffolds based on two polymers, poly[( R)3-hydroxybutyrate] (PHB) and poly[3-hydroxybutyrate- co-3-hydroxyvalerate] (PHBV), are presented. Mineralization of the scaffold surface is carried out by the in situ synthesis of CaCO₃ in the vaterite and calcite polymorphs using ultrasound (U/S). Comparative characterization of PHB and PHBV scaffolds demonstrated an impact of the porosity and surface charge on the mineralization in a dynamic mechanical system, as no essential distinction was observed in wettability, structure, and surface chemical compositions. A significantly higher (4.3 times) piezoelectric charge and a higher porosity (∼15%) lead to a more homogenous CaCO₃ growth in 3-D fibrous structures and result in a two times higher relative mass increase for PHB scaffolds compared to that for PHBV. This also increases the local ion concentration incurred upon mineralization under U/S-generated dynamic mechanical conditions. The modification of the wettability for PHB and PHBV scaffolds from hydrophobic (nonmineralized fibers) to superhydrophilic (mineralized fibers) led to a pronounced apatite-forming behavior of scaffolds in a simulated body fluid. In turn, this results in the formation of a dense monolayer of well-distributed and proliferated osteoblast cells along the fibers. CaCO₃-mineralized PHBV surfaces had a higher osteoblast cell adhesion and proliferation assigned to a higher amount of CaCO₃ on the surface compared to that on PHB scaffolds, as incurred from micro-computed tomography (μCT). Importantly, a cell viability study confirmed biocompatibility of all the scaffolds. Thus, hybrid biocomposites based on the piezoelectric PHB polymers represent an effective scaffold platform functionalized by an inorganic phase and stimulating the growth of the bone tissue.