Nanostructured Brownian surfaces prepared through two-photon polymerization: investigation of stem cell response

Light-mediated intracellular polymerization

The synthesis of synthetic intracellular polymers offers groundbreaking possibilities in cellular biology and medical research, allowing for novel experiments in drug delivery, bioimaging and targeted cancer therapies. These macromolecules, composed of biocompatible monomers, are pivotal in manipulating cellular functions and pathways due to their bioavailability, cytocompatibility and distinct chemical properties. This protocol details two innovative methods for intracellular polymerization. The first one uses 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959) as a photoinitiator for free radical polymerization under UV light (365 nm, 5 mW/cm2). The second method employs photoinduced electron transfer-reversible addition-fragmentation chain-transfer polymerization with visible light (470 nm, 100 mW/cm2). We further elaborate on isolating these intracellular polymers by streptavidin/biotin interaction or immobilized metal ion affinity chromatography for polymers tagged with biotin or histidine. The entire process, from polymerization to isolation, takes ~48 h. Moreover, the intracellular polymers thus generated demonstrate significant potential in enhancing actin polymerization, in bioimaging applications and as a novel avenue in cancer treatment strategies. The protocol extends to animal models, providing a comprehensive approach from cellular to systemic applications. Users are advised to have a basic understanding of organic synthesis and cell biology techniques.

Density Regulation and Localization of Cell Clusters by Self-Assembled Femtosecond-Laser-Fabricated Micropillar Arrays

Tumor cell clusters of varying sizes and densities have different metastatic potentials. Three-dimensional (3D) patterned structures with rational topographical and mechanical properties are capable of guiding the 3D clustering of tumor cells. In this study, single femtosecond laser pulses were used to fabricate individual high-aspect-ratio micropillars via two-photon polymerization (TPP). By combining this approach with capillary-force self-assembly, complex 3D microstructure patterns were constructed with a high efficiency. The microstructures were able to regulate the formation of cell clusters at different cell seeding densities and direct self-guided 3D assembly of cell clusters of various sizes and densities. Localization of cell clusters was achieved using grid-indexed samples to address individual cell clusters, which holds great promise for in situ cell cluster culture and monitoring and for applications such as RNA sequencing of cell clusters.

A Simple Approach for Flexible and Stretchable Anti-icing Lubricant-Infused Tape

Unwanted icing has major safety and economic repercussions on human activities, affecting means of transportation, infrastructures, and consumer goods. Compared to the common deicing methods in use today, intrinsically icephobic surfaces can decrease ice accumulation and formation without any active intervention from humans or machines. However, such systems often require complex fabrication methods and can be costly, which limits their applicability. In this study, we report the preparation and characterization of several slippery lubricant-infused porous surfaces (SLIPSs) realized by impregnating with silicone oil a candle soot layer deposited on double-sided adhesive tape. Despite the use of common household items, these SLIPSs showed anti-icing performance comparable to other systems described in the literature (ice adhesion < 20 kPa) and a good resistance to mechanical and environmental damages in laboratory conditions. The use of a flexible and functional substrate as tape allowed these devices to be stretchable without suffering significant degradation and highlights how these systems can be easily prepared and applied anywhere needed. In addition, the possibility of deforming the substrate can "allow" the application of SLIPS technology in mechanical ice removal methodologies, drastically incrementing their performance.

Synthetic Data in Quantitative Scanning Probe Microscopy

Synthetic data are of increasing importance in nanometrology. They can be used for development of data processing methods, analysis of uncertainties and estimation of various measurement artefacts. In this paper we review methods used for their generation and the applications of synthetic data in scanning probe microscopy, focusing on their principles, performance, and applicability. We illustrate the benefits of using synthetic data on different tasks related to development of better scanning approaches and related to estimation of reliability of data processing methods. We demonstrate how the synthetic data can be used to analyse systematic errors that are common to scanning probe microscopy methods, either related to the measurement principle or to the typical data processing paths.

Direct Laser Writing of Four-Dimensional Structural Color Microactuators Using a Photonic Photoresist

With the advent of direct laser writing using two-photon polymerization, the generation of high-resolution three-dimensional microstructures has increased dramatically. However, the development of stimuli-responsive photoresists to create four-dimensional (4D) microstructures remains a challenge. Herein, we present a supramolecular cholesteric liquid crystalline photonic photoresist for the fabrication of 4D photonic microactuators, such as pillars, flowers, and butterflies, with submicron resolution. These micron-sized features display structural color and shape changes triggered by a variation of humidity or temperature. These findings serve as a roadmap for the design and creation of high-resolution 4D photonic microactuators.

Multifunctional temozolomide-loaded lipid superparamagnetic nanovectors: dual targeting and disintegration of glioblastoma spheroids by synergic chemotherapy and hyperthermia treatment

Aiming at finding new solutions for fighting glioblastoma multiforme, one of the most aggressive and lethal human cancer, here an in vitro validation of multifunctional nanovectors for drug delivery and hyperthermia therapy is proposed. Hybrid magnetic lipid nanoparticles have been fully characterized and tested on a multi-cellular complex model resembling the tumor microenvironment. Investigations of cancer therapy based on a physical approach (namely hyperthermia) and on a pharmaceutical approach (by exploiting the chemotherapeutic drug temozolomide) have been extensively carried out, by evaluating its antiproliferative and pro-apoptotic effects on 3D models of glioblastoma multiforme. A systematic study of transcytosis and endocytosis mechanisms has been moreover performed with multiple complimentary investigations, besides a detailed description of local temperature increments following hyperthermia application. Finally, an in-depth proteomic analysis corroborated the obtained findings, which can be summarized in the preparation of a versatile, multifunctional, and effective nanoplatform able to overcome the blood-brain barrier and to induce powerful anti-cancer effects on in vitro complex models.

Functional Materials for Two-Photon Polymerization in Microfabrication

Direct laser writing methods based on two-photon polymerization (2PP) are powerful tools for the on-demand printing of precise and complex 3D architectures at the micro and nanometer scale. While much progress was made to increase the resolution and the feature size throughout the years, by carefully designing a material, one can confer specific functional properties to the printed structures thus making them appealing for peculiar and novel applications. This Review summarizes the state-of-the-art of functional resins and photoresists used in 2PP, discussing both the range of material functions available and the methods used to prepare them, highlighting advantages and disadvantages of different classes of materials in achieving certain properties.

MSC differentiation on two-photon polymerized, stiffness and BMP2 modified biological copolymers

INTRODUCTION

Bone tissue regeneration requires a three-dimensional biological setting. An ideal scaffold should enable cell proliferation and differentiation by mimicking structure and mechanical properties of the compromised defect as well as carrying growth factors. Two-photon polymerization (2PP) allows the preparation of 3D structures with a micrometric resolution.

METHODS

In this study, 2PP was applied to design scaffolds made from biocompatible methacrylated D,L-lactide-co-ε-caprolactone copolymers (LC) with a controlled porous architecture. Proliferation and differentiation of bone marrow mesenchymal stromal cells on LC was analyzed and compared to a standard inorganic urethane-dimethacrylate (UDMA) matrix. To functionalize LC and UDMA surfaces we analyzed a biomimetic, layer-by-layer coating, which could be modified in stiffness and integration of bone morphogenetic protein 2 (BMP2) and evaluated its effect on osteogenic differentiation.

RESULTS

On LC surfaces, BMSC demonstrated an optimal proliferation within pore sizes of 60-100 μm and showed a continuous expression of Vimentin. On the polyelectrolyte multilayer coating a significant increase in BMSC proliferation and differentiation as marked by Osteonectin expression was achieved using stiffness modification and BMP2 functionalization.

CONCLUSION

Combining 3D-Design with biofunctionalization, LC offers a promising approach for future regenerative applications in osteogenic differentiation of BMSCs.

Hierarchically aligned gradient collagen micropatterns for rapidly screening Schwann cells behavior

To penetrate the effect of protein gradient micropattern on peripheral nerve regeneration, the hierarchically aligned gradient collagen micropattern was prepared by micromoulding method and the influence on Schwann cells growth behavior was studied. The morphology, wettability, stability and component variation of the micropatterns were firstly characterized. Then, Schwann cells were cultured and the related mechanism was penetrated. The results showed that the gradient collagen micropattern could be well fabricated. The surface wettability varied with the change of collagen concentration, and the prepared gradient micropattern showed a good stability after PBS immersion for 15 days. The results of Schwann cells culture and morphological index analysis displayed that the prepared gradient collagen micropatten could well regulate the orientation growth of Schwann cells, while a much better cell alignment growth was obtained on the gradient micropattern with higher collagen concentration and wider pattern size. PCR and WB showed that the micropattern structure could effectively up-regulate the key specific genes for axon regeneration and myelination process. Overall, the study provides a systematic and facile method for understanding the effect of various sized micropatterns on cell behavior, which may have a great significance for the development of artificial implants for tissue engineering and regenerative medicine.

Alleviating Distortion and Improving the Young's Modulus in Two-Photon Polymerization Fabrications

Two-photon polymerization enables the extremely high resolution three-dimensional printing of micro-structures. To know the mechanical properties, and better still, to be able to adjust them is of paramount importance to ensuring the proper structural integrity of the printed products. In this work, the Young’s modulus is measured on two-photon polymerized micro-cantilever bars. Optimizing the scanning trajectory of the laser focus points is important in alleviating distortion of the printed bars. By increasing the laser power and decreasing the inter-voxel distances we can double the Young’s modulus. Post-curing with ultraviolet light can approximately quadruple the Young’s modulus. However, the resulting modulus is still only about 0.3% of that of the bulk polymerized material.

Evaluation of highly carbonated hydroxyapatite bioceramic implant coatings with hierarchical micro-/nanorod topography optimized for osseointegration

Background

Optimal osseointegration has been recognized as a pivotal factor in determining the long-term success of biomedical implants.

Materials and methods

In the current study, highly carbonated hydroxyapatite (CHA) with carbonate contents of 8, 12 and 16 wt% and pure hydroxyapatite (HA) were fabricated via a novel hydrothermal method and deposited on the titanium substrates to generate corresponding CHA bioceramic coatings (designated as C8, C12 and C16, respectively) and HA bioceramic coatings (designated as C0).

Results

C8, C12 and C16 were endowed with nanoscale, hierarchical hybrid micro-/nanoscale and microscale surface topographies with rod-like superstructures, respectively. Compared with C0, the micro-/nanotextured CHA bioceramic coatings (C8, C12 and C16) possessed excellent surface bioactivity and biocompatibility, as well as better wettability, which mediated improved protein adsorption, giving rise to simultaneous enhancement of a biological cascade of events of rat bone-marrow-derived mesenchymal stem cells including cell adhesion, proliferation, osteogenic differentiation and, notably, the production of the pro-angiogenic growth factor, vascular endothelial growth factor-A. In particular, C12 with biomimetic hierarchical hybrid micro-/nanorod topography exhibited superior fractal property and predominant performance of protein adsorption, cell adhesion, proliferation and osteogenesis concomitant with angiogenesis.

Conclusion

All these results suggest that the 12 wt% CHA bioceramic coating with synergistic modification of surface chemistry and topography has great prospect for future use as implant coating to achieve optimum osseointegration for orthopedic and dental applications.

Interaction of cells with patterned reactors

The patterning of subcompartmentalized enzyme-loaded reactors is illustrated and the effect of triggered encapsulated catalysis on adhering cells is reported.

Development of a microfluidic platform integrating high-resolution microstructured biomaterials to study cell-material interactions

Microfluidic screening platforms offer new possibilities for performing in vitro cell-based assays with higher throughput and in a setting that has the potential to closely mimic the physiological microenvironment. Integrating functional biomaterials into such platforms is a promising approach to obtain a deeper insight into the interactions occurring at the cell-material interface. The success of such an approach is, however, largely dependent on the ability to miniaturize the biomaterials as well as on the choice of the assay used to study the cell-material interactions. In this work, we developed a microfluidic device, the main component of which is made of a widely used biocompatible polymer, polylactic acid (PLA). This device enabled cell culture under different fluidic regimes, including perfusion and diffusion. Through a combination of photolithography, two-photon polymerization and hot embossing, it was possible to microstructure the surface of the cell culture chamber of the device with highly defined geometrical features. Furthermore, using pyramids with different heights and wall microtopographies as an example, adhesion, morphology and distribution of human MG63 osteosarcoma cells were studied. The results showed that both the height of the topographical features and the microstructural properties of their walls affected cell spreading and distribution. This proof-of-concept study shows that the platform developed here is a useful tool for studying interactions between cells and clinically relevant biomaterials under controlled fluidic regimes.

Quantification of Type, Timing, and Extent of Cell Body and Nucleus Deformations Caused by the Dimensions and Hydrophilicity of Square Prism Micropillars

Novel digital analysis strategies are developed for the quantification of changes in the cytoskeletal and nuclear morphologies of mesenchymal stem cells cultured on micropillars. Severe deformations of nucleus and distinct conformational changes of cell body ranging from extensive elongation to branching are visualized and quantified. These deformations are caused mainly by the dimensions and hydrophilicity of the micropillars.

Laser Nano-Neurosurgery from Gentle Manipulation to Nano-Incision of Neuronal Cells and Scaffolds: An Advanced Neurotechnology Tool

Current optical approaches are progressing far beyond the scope of monitoring the structure and function of living matter, and they are becoming widely recognized as extremely precise, minimally-invasive, contact-free handling tools. Laser manipulation of living tissues, single cells, or even single-molecules is becoming a well-established methodology, thus founding the onset of new experimental paradigms and research fields. Indeed, a tightly focused pulsed laser source permits complex tasks such as developing engineered bioscaffolds, applying calibrated forces, transfecting, stimulating, or even ablating single cells with subcellular precision, and operating intracellular surgical protocols at the level of single organelles. In the present review, we report the state of the art of laser manipulation in neuroscience, to inspire future applications of light-assisted tools in nano-neurosurgery.

Modulation of cellular responses: The two-photon polymerization approach in the control of the physical micro/nanoenvironment

Cells and tissues are extremely sensitive to their physico-chemical surroundings: in regenerative medicine, as an example, the maintenance of culture conditions resembling the in vivo environment is essential for a correct tissue development. In this review, we summarize our results concerning the preparation and testing of micro/nanostructures for fostering peculiar cellular behavior, prepared by exploiting an innovative technique of high resolution 3D photolithography, the two-photon polymerization (2pp).

Biomimicry at the nanoscale: current research and perspectives of two-photon polymerization

Living systems such as cells and tissues are extremely sensitive to their surrounding physico-chemical microenvironment. In the field of regenerative medicine and tissue engineering, the maintenance of culture conditions suitable for the formation of proliferation niches, for the self-renewal maintenance of stem cells, or for the promotion of a particular differentiation fate is an important issue that has been addressed using different strategies. A number of investigations suggests that a particular cell behavior can be in vitro resembled by mimicking the corresponding in vivo conditions. In this context, several biomimetic environments have been designed in order to control cell phenotypes and functions. In this review, we will analyze the most recent examples of the control of the in vitro physical micro/nano-environment by exploiting an innovative technique of high resolution 3D photolithography, the two-photon polymerization (2pp). The biomedical applications of this versatile and disruptive computer assisted design/manufacturing technology are very wide, and range from the fabrication of biomimetic and nanostructured scaffolds for tissue engineering and regenerative medicine, to the microfabrication of biomedical devices, like ossicular replacement prosthesis and microneedles.