Light-assisted electrospinning monitoring for soft polymeric nanofibers.

A real-time tool to monitor the electrospinning process is fundamental to improve the reproducibility and quality of the resulting nanofibers. Hereby, a novel optical system integrated through coaxial needle is proposed as monitoring tool for electrospinning process. An optical fiber (OF) is inserted in the inner needle, while the external needle is used to feed the polymeric solution (PEO/water) drawn by the process. The light exiting the OF passes through the solution drop at the needle tip and gets coupled to the electrospun fiber (EF) while travelling towards the nanofibers collector. Numerical and analytical models were developed to assess the feasibility and robustness of the light coupling. Experimental tests demonstrated the influence of the process parameters on the EF waveguide properties, in terms of waveguide length (L), and on the nanofibers diameter distribution, in terms of mean [Formula: see text] and normalized standard deviation [Formula: see text]. Data analysis reveals good correlation between L and [Formula: see text] (respectively maximum correlation coefficients of [Formula: see text] = 0.88 and [Formula: see text] = 0.84), demonstrating the potential for effectively using the proposed light-assisted technology as real-time visual feedback on the process. The developed system can provide an interesting option for monitoring industrial electrospinning systems using multi- or moving needles with impact in the scaling-up of innovative nanofibers for soft systems.

A 3D Real-Scale, Biomimetic, and Biohybrid Model of the Blood-Brain Barrier Fabricated through Two-Photon Lithography.

The investigation of the crossing of exogenous substances through the blood-brain barrier (BBB) is object of intensive research in biomedicine, and one of the main obstacles for reliable in vitro evaluations is represented by the difficulties at the base of developing realistic models of the barrier, which could resemble as most accurately as possible the in vivo environment. Here, for the first time, a 1:1 scale, biomimetic, and biohybrid BBB model is proposed. Microtubes inspired to the brain capillaries were fabricated through two-photon lithography and used as scaffolds for the co-culturing of endothelial-like bEnd.3 and U87 glioblastoma cells. The constructs show the maturation of tight junctions, good performances in terms of hindering dextran diffusion through the barrier, and a satisfactory trans-endothelial electrical resistance. Moreover, a mathematical model is developed, which assists in both the design of the 3D microfluidic chip and its characterization. Overall, these results show the effective formation of a bioinspired cellular barrier based on microtubes reproducing brain microcapillaries to scale. This system will be exploited as a realistic in vitro model for the investigation of BBB crossing of nanomaterials and drugs, envisaging therapeutic and diagnostic applications for several brain pathologies, including brain cancer.

Three-Dimensional Soft Material Micropatterning via Direct Laser Lithography of Flexible Molds.

Three-dimensionally micropatterned surfaces are attracting increasing interest in soft robotics owing to the potential of mimicking natural morphologies at the micro/nanoscale. We employ direct laser lithography to fabricate molds with complex three-dimensional (3D) micrometric features, in a positive photoresist on flexible substrates, to pattern curved macroscopic soft surfaces with shapes not achievable with standard methods (e.g., reentrant angles). We present several 3D intricate microstructures in poly(dimethylsiloxane) (PDMS) and show a soft cylinder patterned with 3D microstructures with one molding process. Finally, we deform PDMS-based 3D architectures and show soft microgripping capability, indicating the potentiality of this approach for future application in soft robotics.

Nanostructured ultra-thin patches for ultrasound-modulated delivery of anti-restenotic drug.

This work aims to demonstrate the possibility to fabricate ultra-thin polymeric films loaded with an anti-restenotic drug and capable of tunable drug release kinetics for the local treatment of restenosis. Vascular nanopatches are composed of a poly(lactic acid) supporting membrane (thickness: ~250 nm) on which 20 polyelectrolyte bilayers (overall thickness: ~70 nm) are alternatively deposited. The anti-restenotic drug is embedded in the middle of the polyelectrolyte structure, and released by diffusion mechanisms. Nanofilm fabrication procedure and detailed morphological characterization are reported here. Barium titanate nanoparticles (showing piezoelectric properties) are included in the polymeric support and their role is investigated in terms of influence on nanofilm morphology, drug release kinetics, and cell response. Results show an efficient drug release from the polyelectrolyte structure in phosphate-buffered saline, and a clear antiproliferative effect on human smooth muscle cells, which are responsible for restenosis. In addition, preliminary evidences of ultrasound-mediated modulation of drug release kinetics are reported, thus evaluating the influence of barium titanate nanoparticles on the release mechanism. Such data were integrated with quantitative piezoelectric and thermal measurements. These results open new avenues for a fine control of local therapies based on smart responsive materials.

Two-Photon Lithography of 3D Nanocomposite Piezoelectric Scaffolds for Cell Stimulation.

In this letter, we report on the fabrication, the characterization, and the in vitro testing of structures suitable for cell culturing, prepared through two-photon polymerization of a nanocomposite resist. More in details, commercially available Ormocomp has been doped with piezoelectric barium titanate nanoparticles, and bioinspired 3D structures resembling trabeculae of sponge bone have been fabricated. After an extensive characterization, preliminary in vitro testing demonstrated that both the topographical and the piezoelectric cues of these scaffolds are able to enhance the differentiation process of human SaOS-2 cells.

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.

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

Nondeterministic phenomena are at the base of plenty of biological processes that comprise physiological signaling, cellular communications, and biological architectures. Among them, natural surface topographies are often characterized by "chaotic" features that are not trivial to be recreated in vitro. Recently, some methods have been proposed to resemble the hierarchical organization of the extracellular microenvironment, through the chemical preparation of randomly rough and self-affine fractal surfaces. Notwithstanding, this approach does not allow the fractal dimension to be modulated at a desired value, being moreover the self-affinity maintained just for one decade of spatial frequencies. Here, we propose the replication of in silico generated Brownian surfaces through a two-photon polymerization technique. As a result of the direct laser writing of the desired patterns, we were able to obtain highly reproducible self-affine (in a range of two spatial frequency decades) structures characterized by the desired predetermined Hurst exponents. Rat mesenchymal stem cells were moreover cultured on the obtained substrates, highlighting interesting phenomena concerning cell adhesion, cytoskeleton conformation, and actin polymerization, strictly depending on the fractal dimension of the surfaces.

The Osteoprint: a bioinspired two-photon polymerized 3-D structure for the enhancement of bone-like cell differentiation.

The need for a better understanding of cell behavior and for exploiting cell functions in various healthcare applications has driven biomedical research to develop increasingly complex fabrication strategies to reproduce the natural biological microenvironment in vitro. Different approaches have led to the development of refined examples of 2- and 3-D structures able to sustain cellular proliferation, differentiation and functionality very similar to those normally occurring in living organisms. One such approach is two-photon polymerization. In this paper, we present a trabecula-like structure (which we have named "Osteoprint") that resembles to the typical microenvironment of trabecular bone cells. Starting from microtomography images of the trabecular bone, we prepared several Osteoprints through two-photon polymerization and tested the behavior of SaOS-2 bone-like cells cultured on our structures. Interestingly, we found that Osteoprints deeply affect cellular behavior, determining an exit from the cell cycle and an enhancement of osteogenic differentiation. Indeed, we found an up-regulation of the genes involved in SaOS-2 cell maturation and an increase in hydroxyapatite production and accumulation upon SaOS-2 culture on the Osteoprints. The findings we obtained are extremely interesting, and open up new perspectives in "bioinspired" approaches for tissue engineering and regenerative medicine.

Two-photon polymerization of sub-micrometric patterned surfaces: investigation of cell-substrate interactions and improved differentiation of neuron-like cells.

Direct Laser Writing (DLW) is an innovative tool that allows the photofabrication of high resolution 3D structures, which can be successfully exploited for the study of the physical interactions between cells and substrates. In this work, we focused our attention on the topographical effects of submicrometric patterned surfaces fabricated via DLW on neuronal cell behavior. In particular, we designed, prepared, and characterized substrates based on aligned ridges for the promotion of axonal outgrowth and guidance. We demonstrated that both rat PC12 neuron-like cells and human SH-SY5Y derived neurons differentiate on parallel 2.5 µm spaced submicrometric ridges, being characterized by strongly aligned and significantly longer neurites with respect to those differentiated on flat control substrates, or on more spaced (5 and 10 µm) ridges. Furthermore, we detected an increased molecular differentiation toward neurons of the SH-SY5Y cells when grown on the submicrometric patterned substrates. Finally, we observed that the axons can exert forces able of bending the ridges, and we indirectly estimated the order of magnitude of these forces thanks to scanning probe techniques. Collectively, we showed as submicrometric structures fabricated by DLW can be used as a useful tool for the study of the axon mechanobiology.

Boron nitride nanotube-mediated stimulation of cell co-culture on micro-engineered hydrogels.

In this paper, we describe the effects of the combination of topographical, mechanical, chemical and intracellular electrical stimuli on a co-culture of fibroblasts and skeletal muscle cells. The co-culture was anisotropically grown onto an engineered micro-grooved (10 µm-wide grooves) polyacrylamide substrate, showing a precisely tuned Young's modulus (∼ 14 kPa) and a small thickness (∼ 12 µm). We enhanced the co-culture properties through intracellular stimulation produced by piezoelectric nanostructures (i.e., boron nitride nanotubes) activated by ultrasounds, thus exploiting the ability of boron nitride nanotubes to convert outer mechanical waves (such as ultrasounds) in intracellular electrical stimuli, by exploiting the direct piezoelectric effect. We demonstrated that nanotubes were internalized by muscle cells and localized in both early and late endosomes, while they were not internalized by the underneath fibroblast layer. Muscle cell differentiation benefited from the synergic combination of topographical, mechanical, chemical and nanoparticle-based stimuli, showing good myotube development and alignment towards a preferential direction, as well as high expression of genes encoding key proteins for muscle contraction (i.e., actin and myosin). We also clarified the possible role of fibroblasts in this process, highlighting their response to the above mentioned physical stimuli in terms of gene expression and cytokine production. Finally, calcium imaging-based experiments demonstrated a higher functionality of the stimulated co-cultures.

Barium titanate core--gold shell nanoparticles for hyperthermia treatments.

The development of new tools and devices to aid in treating cancer is a hot topic in biomedical research. The practice of using heat (hyperthermia) to treat cancerous lesions has a long history dating back to ancient Greece. With deeper knowledge of the factors that cause cancer and the transmissive window of cells and tissues in the near-infrared region of the electromagnetic spectrum, hyperthermia applications have been able to incorporate the use of lasers. Photothermal therapy has been introduced as a selective and noninvasive treatment for cancer, in which exogenous photothermal agents are exploited to achieve the selective destruction of cancer cells. In this manuscript, we propose applications of barium titanate core-gold shell nanoparticles for hyperthermia treatment against cancer cells. We explored the effect of increasing concentrations of these nanoshells (0-100 µg/mL) on human neuroblastoma SH-SY5Y cells, testing the internalization and intrinsic toxicity and validating the hyperthermic functionality of the particles through near infrared (NIR) laser-induced thermoablation experiments. No significant changes were observed in cell viability up to nanoparticle concentrations of 50 µg/mL. Experiments upon stimulation with an NIR laser revealed the ability of the nanoshells to destroy human neuroblastoma cells. On the basis of these findings, barium titanate core-gold shell nanoparticles resulted in being suitable for hyperthermia treatment, and our results represent a promising first step for subsequent investigations on their applicability in clinical practice.

Synthesizing tubular and trapezoidal shaped ZnO nanowires by an aqueous solution method.

In this paper we present a novel bottom-up method suitable for developing vertically aligned hollow ZnO nanowires, ZnO nanotubes as well as longitudinally half ZnO nanowires. The procedures used for synthesizing such crystals combine chemical and electrochemical growth processes in aqueous solution at low temperatures (<90 °C), with a growth block process. A thin layer of gold, deposited when the nanowire growth process is at half way, has the crucial role of blocking the growth along the intended directions. The possibility of fabricating highly aligned crystals on a wide range of polymeric substrates, including flexible or transparent ones, is also illustrated. Our proposed methods hold potential for new developments in piezotronics and piezophotonics by allowing fabrication of nanodevices in the inner region of the hollow nanowires and nanotubes.