Recent advances in superhydrophobic surfaces and their relevance to biology and medicine

Advancements in Mid-Infrared spectroscopy of extracellular vesicles

Extracellular vesicles (EVs) are lipid vesicles secreted by all cells into the extracellular space and act as nanosized biological messengers among cells. They carry a specific molecular cargo, composed of lipids, proteins, nucleic acids, and carbohydrates, which reflects the state of their parent cells. Due to their remarkable structural and compositional heterogeneity, characterizing EVs, particularly from a biochemical perspective, presents complex challenges. In this context, mid-infrared (IR) spectroscopy is emerging as a valuable tool, providing researchers with a comprehensive and label-free spectral fingerprint of EVs in terms of their specific molecular content. This review aims to provide an up-to-date critical overview of the major advancements in mid-IR spectroscopy of extracellular vesicles, encompassing both fundamental and applied research achievements. We also systematically emphasize the new possibilities offered by the integration of emerging cutting-edge IR technologies, such as tip-enhanced and surface-enhanced spectroscopy approaches, along with the growing use of machine learning for data analysis and spectral interpretation. Additionally, to assist researchers in navigating this intricate subject, our manuscript includes a wide and detailed collection of the spectral peaks that have been assigned to EV molecular constituents up to now in the literature.

From biomimetics to smart materials and 3D technology: Applications in orthodontic bonding, debonding, and appliance design or fabrication

This review covers aspects of orthodontic materials, appliance fabrication and bonding, crossing scientific fields and presenting recent advances in science and technology. Its purpose is to familiarize the reader with developments on these issues, indicate possible future applications of such pioneering approaches, and report the current status in orthodontics. The first section of this review covers shape-memory polymer wires, several misconceptions arising from the recent introduction of novel three-dimensional (3D)-printed aligners (mistakenly termed shape-memory polymers only because they present a certain degree of rebound capacity, as most non-stiff alloys or polymers do), frictionless surfaces enabling resistance-less sliding, self-healing materials for effective handling of fractured plastic/ceramic brackets, self-cleaning materials to minimize microbial attachment or plaque build-up on orthodontic appliances, elastomers with reduced force relaxation and extended stretching capacity to address the problem of inadequate force application during wire-engagement in the bracket slot, biomimetic (non-etching mediated) adhesive attachment to surfaces based on the model of the gecko and the mussel, and command-debond adhesives as options for an atraumatic debonding. This review's second section deals with the recent and largely unsubstantiated application of 3D-printed alloys and polymers in orthodontics and aspects of planning, material fabrication, and appliance design.

Antenna-enhanced mid-infrared detection of extracellular vesicles derived from human cancer cell cultures

BACKGROUND

Extracellular Vesicles (EVs) are sub-micrometer lipid-bound particles released by most cell types. They are considered a promising source of cancer biomarkers for liquid biopsy and personalized medicine due to their specific molecular cargo, which provides biochemical information on the state of parent cells. Despite this potential, EVs translation process in the diagnostic practice is still at its birth, and the development of novel medical devices for their detection and characterization is highly required.

RESULTS

In this study, we demonstrate mid-infrared plasmonic nanoantenna arrays designed to detect, in the liquid and dry phase, the specific vibrational absorption signal of EVs simultaneously with the unspecific refractive index sensing signal. For this purpose, EVs are immobilized on the gold nanoantenna surface by immunocapture, allowing us to select specific EV sub-populations and get rid of contaminants. A wet sample-handling technique relying on hydrophobicity contrast enables effortless reflectance measurements with a Fourier-transform infrared (FTIR) spectro-microscope in the wavelength range between 10 and 3 µm. In a proof-of-principle experiment carried out on EVs released from human colorectal adenocarcinoma (CRC) cells, the protein absorption bands (amide-I and amide-II between 5.9 and 6.4 µm) increase sharply within minutes when the EV solution is introduced in the fluidic chamber, indicating sensitivity to the EV proteins. A refractive index sensing curve is simultaneously provided by our sensor in the form of the redshift of a sharp spectral edge at wavelengths around 5 µm, where no vibrational absorption of organic molecules takes place: this permits to extract of the dynamics of EV capture by antibodies from the overall molecular layer deposition dynamics, which is typically measured by commercial surface plasmon resonance sensors. Additionally, the described metasurface is exploited to compare the spectral response of EVs derived from cancer cells with increasing invasiveness and metastatic potential, suggesting that the average secondary structure content in EVs can be correlated with cell malignancy.

CONCLUSIONS

Thanks to the high protein sensitivity and the possibility to work with small sample volumes-two key features for ultrasensitive detection of extracellular vesicles- our lab-on-chip can positively impact the development of novel laboratory medicine methods for the molecular characterization of EVs.

3D Printed Biomimetic Metamaterials with Graded Porosity and Tapering Topology for Improved Cell Seeding and Bone Regeneration

Biomimetic metallic biomaterials prepared for bone scaffolds have drawn more and more attention in recent years. However, the topological design of scaffolds is critical to cater to multi-physical requirements for efficient cell seeding and bone regeneration, yet remains a big scientific challenge owing to the coupling of mechanical and mass-transport properties in conventional scaffolds that lead to poor control towards favorable modulus and permeability combinations. Herein, inspired by the microstructure of natural sea urchin spines, biomimetic scaffolds constructed by pentamode metamaterials (PMs) with hierarchical structural tunability were additively manufactured via selective laser melting. The mechanical and mass-transport properties of scaffolds could be simultaneously tuned by the graded porosity (B/T ratio) and the tapering level (D/d ratio). Compared with traditional metallic biomaterials, our biomimetic PM scaffolds possess graded pore distribution, suitable strength, and significant improvements to cell seeding efficiency, permeability, and impact-tolerant capacity, and they also promote in vivo osteogenesis, indicating promising application for cell proliferation and bone regeneration using a structural innovation.

Micro/Nanopatterned Superhydrophobic Surfaces Fabrication for Biomolecules and Biomaterials Manipulation and Analysis

Superhydrophobic surfaces display an extraordinary repulsion to water and water-based solutions. This effect emerges from the interplay of intrinsic hydrophobicity of the surface and its morphology. These surfaces have been established for a long time and have been studied for decades. The increasing interest in recent years has been focused towards applications in many different fields and, in particular, biomedical applications. In this paper, we review the progress achieved in the last years in the fabrication of regularly patterned superhydrophobic surfaces in many different materials and their exploitation for the manipulation and characterization of biomaterial, with particular emphasis on the issues affecting the yields of the fabrication processes and the quality of the manufactured devices.

Recent Advances in the Label-Free Characterization of Exosomes for Cancer Liquid Biopsy: From Scattering and Spectroscopy to Nanoindentation and Nanodevices

Exosomes (EXOs) are nano-sized vesicles secreted by most cell types. They are abundant in bio-fluids and harbor specific molecular constituents from their parental cells. Due to these characteristics, EXOs have a great potential in cancer diagnostics for liquid biopsy and personalized medicine. Despite this unique potential, EXOs are not yet widely applied in clinical settings, with two main factors hindering their translational process in diagnostics. Firstly, conventional extraction methods are time-consuming, require large sample volumes and expensive equipment, and often do not provide high-purity samples. Secondly, characterization methods have some limitations, because they are often qualitative, need extensive labeling or complex sampling procedures that can induce artifacts. In this context, novel label-free approaches are rapidly emerging, and are holding potential to revolutionize EXO diagnostics. These methods include the use of nanodevices for EXO purification, and vibrational spectroscopies, scattering, and nanoindentation for characterization. In this progress report, we summarize recent key advances in label-free techniques for EXO purification and characterization. We point out that these methods contribute to reducing costs and processing times, provide complementary information compared to the conventional characterization techniques, and enhance flexibility, thus favoring the discovery of novel and unexplored EXO-based biomarkers. In this process, the impact of nanotechnology is systematically highlighted, showing how the effectiveness of these techniques can be enhanced using nanomaterials, such as plasmonic nanoparticles and nanostructured surfaces, which enable the exploitation of advanced physical phenomena occurring at the nanoscale level.

Co-inspired hydroxyapatite-based scaffolds for vascularized bone regeneration

Hydroxyapatite (HA) is the main inorganic component of human bone. Inspired by nacre and cortical bone, hydroxyapatite-based coil scaffolds were successfully prepared. The scaffolds presented "brick and mortar" multi-layered structure of nacre and multi-layered concentric circular structure of cortical bone. Because of bioactive components and hierarchical structure, the scaffolds possessed good compressive strength (≈95 MPa), flexural strength (≈161 MPa) and toughness (≈1.1 MJ/m³). In addition, they showed improved angiogenesis and osteogenesis in rat and rabbit critical sized bone defect models. By mimicking co-biological systems, this work provided a feasible strategy to optimize the properties of traditional tissue engineering biological materials for vascularized bone regeneration.

Reconfigurable Surface with Photodefinable Physicochemical Properties for User-Designable Cell Scaffolds

Surfaces with specific topography and chemical composition are quite useful in many applications ranging from functional interfaces to cell incubation scaffolds. Although these surfaces can be easily fabricated by combining topography-construction methods and surface-functionalization strategies, their properties are often static after fabrication or merely switchable between "on" and "off" states. Developing surfaces that can be on-demand regulated are quite important for the generation of smart surfaces for future applications. In this paper, we present a reconfigurable surface with adjustable topography and chemical functionality utilizing the photodynamic feature of the disulfide bond. Structured surfaces, composed of disulfide-cross-linked polymer networks, were prepared by using disulfide-containing methacrylate as the monomer. We show that the topography and chemical functionality of the surface can be on-demand regulated after its fabrication, with 254 and 365 nm UV light, respectively, allowing to "define" the physicochemical properties of the surface using light before the usage. We also demonstrate the application of such surface as a user-designable cell scaffold, that different cell scaffolds can be generated from one original surface with a simple exposure process, to define the desired bioactivity onto every point of the surface and therefore exactly control cell behaviors on the scaffold.

In-air production of 3D co-culture tumor spheroid hydrogels for expedited drug screening

Three-dimensional (3D) in vitro tumor spheroids are becoming popular as pre-clinical platforms for testing the performance of existing drugs or for discovery of innovative anti-cancer therapeutics. This focus is correlated with in vitro 3D tumor models ability to mimic the multicellular compact structure and spatial architecture of human solid tumors. However, these microphysiological systems generally lack the pre-existence of tumor-ECM, a critical aspect that can affect the overall therapeutic performance and the decision of advancing candidate drugs to later stages of the pipeline. Aiming to face this drawback and mimic tumors-ECM, herein we rapidly fabricated in-air hyaluronan-methacrylate (HA-MA) and gelatin-methacrylate (GelMA) photocrosslinkable 3D spheroid microgels by using superhydrophobic surfaces. These platforms were used for establishing heterotypic 3D co-culture models of prostate cancer cells (PC-3) and human osteoblasts (hOB) to mimic prostate cancer-to-bone metastasis cellular heterogeneity and the tumor-ECM microenvironment. 3D microgel microtumors morphology, size and cell number were easily controlled via digital droplet generation on polystyrene superhydrophobic surfaces and under solvent-free conditions when compared to microfluidics or electrospray. Co-culture 3D microgels formed by 2.5%HA-MA-5%GelMA and 5%HA-MA-5%GelMA ratios showed the highest calcium deposition after 14 days of culture, evidencing osteoblasts viability and the establishment of functional mineralization in the 3D hydrogel matrix. Cisplatin cytotoxicity evaluation showed that 3D microgels are more resistant to platin chemotherapeutics than single or co-culture 3D multicellular spheroid counterparts. Overall, our findings indicate that solvent-free, in-air produced 3D microgel microenvironments are cost-effective and robust tumor mimicking platforms for in vitro high-throughput screening of therapeutics targeted to prostate-to-bone metastasis microenvironments. STATEMENT OF SIGNIFICANCE: The generation of robust microphysiological systems that recapitulate the complexity of the metastatic prostate-to-bone tumor microenvironment is crucial for pre-clinical evaluation of new therapeutics that can eradicate these secondary tumors. In this study, we employed superhydrophobic (SH) surfaces to rapidly fabricate photocrosslinkable hyaluronan-methacrylate/gelatin-methacrylate 3D spheroid microgels for prostate cancer cells and human osteoblasts co-culture models that simultaneously mimic the cellular and ECM tumor components. The use of SH platforms overcomes the issues of standard in-liquid microgel production technologies by providing a robust control over 3D microgels size/morphology and cell-cell co-encapsulation numbers, while avoiding the use of oil-based microgel droplets generation. Overall, SH surfaces allowed a solvent-free, cost-effective, reproducible and adaptable fabrication of heterotypic 3D spherical microgels for high throughput drug screening.

Mobility of Aqueous and Binary Mixture Drops on Lubricating Fluid-Coated Slippery Surfaces

The mobility of liquid drops on lubricant-infused slippery surfaces depends strongly on various system parameters, for example, surface energy and roughness of the underlying solid surface and surface tension and viscosity of the test and the lubricating fluids. Here, we investigate lubricant-coated slippery surfaces fabricated on smooth hydrophobic solid surfaces and examine the influence of thickness and viscosity of the lubricating oil on the velocity of aqueous drops. We also investigate the effect of surface tension of the test liquid using a binary mixture of water and ethanol, on the apparent contact angle, which further affects their slip velocity. A theoretical model, based on various dissipative forces acting in different regions of the lubricating oil and a test drop, is also presented, which elucidates the dependence of drop velocity on lubricating oil viscosity and base radius of drops of test liquids.

Evolution of Complexity in Out-of-Equilibrium Systems by Time-Resolved or Space-Resolved Synchrotron Radiation Techniques

Out-of-equilibrium phenomena are attracting high interest in physics, materials science, chemistry and life sciences. In this state, the study of structural fluctuations at different length scales in time and space are necessary to achieve significant advances in the understanding of the structure-functionality relationship. The visualization of patterns arising from spatiotemporal fluctuations is nowadays possible thanks to new advances in X-ray instrumentation development that combine high-resolution both in space and in time. We present novel experimental approaches using high brilliance synchrotron radiation sources, fast detectors and focusing optics, joint with advanced data analysis based on automated statistical, mathematical and imaging processing tools. This approach has been used to investigate structural fluctuations in out-of-equilibrium systems in the novel field of inhomogeneous quantum complex matter at the crossing point of technology, physics and biology. In particular, we discuss how nanoscale complexity controls the emergence of high-temperature superconductivity (HTS), myelin functionality and formation of hybrid organic-inorganic supramolecular assembly. The emergent complex geometries, opening novel venues to quantum technology and to the development of quantum physics of living systems, are discussed.

Fabrication, multi-scale characterization and in-vitro evaluation of porous hybrid bioactive glass polymer-coated scaffolds for bone tissue engineering

Bioactive glass-based scaffolds are commonly used in bone tissue engineering due to their biocompatibility, mechanical strength and adequate porous structure. However, their hydrophobicity and brittleness limits their practical application. In this study, to improve nanomechanical properties of such scaffolds, pure bioactive hybrid glass and two bioactive hybrid glass-polymer coated composites were fabricated. A complementary micro and nanoscale characterization techniques (SEM, AFM, μCT, FTIR, compressive test, goniometer) were implemented for detailed description of architecture and physicochemical properties of hybrid bioactive glass-based scaffolds with emphasis on nano-mechanics. The final step was in-vitro evaluation of three dimensional macroporous structures. Our findings show that after polymer addition, architecture, topography and surface properties of the scaffolds were changed and promoted favoured behaviour of the cells.

In-situ ATR-FTIR for dynamic analysis of superhydrophobic breakdown on nanostructured silicon surfaces

Superhydrophobic surfaces are highly promising for self-cleaning, anti-fouling and anti-corrosion applications. However, accurate assessment of the lifetime and sustainability of super-hydrophobic materials is hindered by the lack of large area characterization of superhydrophobic breakdown. In this work, attenuated total reflectance−Fourier transform infrared spectroscopy (ATR-FTIR) is explored for a dynamic study of wetting transitions on immersed superhydrophobic arrays of silicon nanopillars. Spontaneous breakdown of the superhydrophobic state is triggered by in-situ modulation of the liquid surface tension. The high surface sensitivity of ATR-FTIR allows for accurate detection of local liquid infiltration. Experimentally determined wetting transition criteria show significant deviations from predictions by classical wetting models. Breakdown kinetics is found to slow down dramatically when the liquid surface tension approaches the transition criterion, which clearly underlines the importance of more accurate wetting analysis on large-area surfaces. Precise actuation of the superhydrophobic breakdown process is demonstrated for the first time through careful modulation of the liquid surface tension around the transition criterion. The developed ATR-FTIR method can be a promising technique to study wetting transitions and associated dynamics on various types of superhydrophobic surfaces.

Optimization of the Synthesis of Superhydrophobic Carbon Nanomaterials by Chemical Vapor Deposition

Demand is increasing for superhydrophobic materials in many applications, such as membrane distillation, separation and special coating technologies. In this study, we report a chemical vapor deposition (CVD) process to fabricate superhydrophobic carbon nanomaterials (CNM) on nickel (Ni)-doped powder activated carbon (PAC). The reaction temperature, reaction time and H₂/C₂H₂ gas ratio were optimized to achieve the optimum contact angle (CA) and carbon yield (CY). For the highest CY (380%) and CA (177°), the optimal reaction temperatures were 702 °C and 687 °C, respectively. However, both the reaction time (40 min) and gas ratio (1.0) were found to have similar effects on CY and CA. Based on the Field emission scanning electron microscopy and transmission electron microscopy images, the CNM could be categorized into two main groups: a) carbon spheres (CS) free carbon nanofibers (CNFs) and b) CS mixed with CNFs, which were formed at 650 and 750 °C, respectively. Raman spectroscopy and thermogravimetric analysis also support this finding. The hydrophobicity of the CNM, expressed by the CA, follows the trend of CS-mixed CNFs (CA: 177°) > CS-free CNFs (CA: 167°) > PAC/Ni (CA: 65°). This paves the way for future applications of synthesized CNM to fabricate water-repellent industrial-grade technologies.

Durable superhydrophobic and superamphiphobic polymeric surfaces and their applications: A review

Wetting control is essential for many applications, such as self-cleaning, anti-icing, anti-fogging, antibacterial action as well as anti-reflection and friction control. While significant effort has been devoted to fabricate superhydrophobic/superamphiphobic surfaces (repellent to water and other low surface tension liquids), very few polymeric superhydrophobic/superamphiphobic surfaces can be considered as durable against various externally imposed stresses (e.g. application of heating, pressure, mechanical forces, chemical, etc.). Therefore, durability tests are extremely important for applications especially when such surfaces are made of "soft" materials. Here, we review the most recent and promising efforts reported towards the realization of durable, superhydrophobic/superamphiphobic, polymeric surfaces emphasizing the durability tests performed, and some important applications. We compare and put in context the scattered durability tests reported in the literature, and present conclusions, perspectives and challenges in the field.

3D Printing of Lotus Root-Like Biomimetic Materials for Cell Delivery and Tissue Regeneration

Biomimetic materials have drawn more and more attention in recent years. Regeneration of large bone defects is still a major clinical challenge. In addition, vascularization plays an important role in the process of large bone regeneration and microchannel structure can induce endothelial cells to form rudimentary vasculature. In recent years, 3D printing scaffolds are major materials for large bone defect repair. However, these traditional 3D scaffolds have low porosity and nonchannel structure, which impede angiogenesis and osteogenesis. In this study, inspired by the microstructure of natural plant lotus root, biomimetic materials with lotus root-like structures are successfully prepared via a modified 3D printing strategy. Compared with traditional 3D materials, these biomimetic materials can significantly improve in vitro cell attachment and proliferation as well as promote in vivo osteogenesis, indicating potential application for cell delivery and bone regeneration.

Different effects of matrix degrading enzymes towards biofilms formed by E. faecalis and E. faecium clinical isolates

E. faecalis and E. faecium cause urinary tract infections highly resistant to therapies due to a protective extracellular matrix. To exploit a new strategy able to treat infections without increasing antibiotic doses, we used enzymes targeting specific biofilm matrix components in combination with Vancomycin. We investigated the activity of Vancomycin combined with two matrix-degrading enzymes, Alginate Lyase (AlgL) and Deoxyribonuclease I (DNase I) against in vitro biofilm of E. faecalis and E. faecium clinical isolates. The heterogeneity of matrix composition leads to defined physiological responses of biofilm communities to their environment: we demonstrated that the use of DNase I and AlgL enzymes affects biofilm structure, cell viability and reduces MBEC values of Vancomycin in E. faecalis and E. faecium, respectively.