Drug delivery through microneedles

\u3cp\u3eDrug delivery through microneedles is a new form of a pharmaceutical dosage system. While single microneedles have been clinically applied already, the out-of-plane integration of a multitude of microneedles in a pharmaceutical patch is a disruptive technology. To take advantage of micro- and nanofluidics, such active patches utilize microneedle array (MNA) technology. MNAs are microsystems that adopt their technical uniqueness by the choice of a fabrication technology. MNAs can be made of solid, hollow, porous, or dissolvable materials in a cost-effective manner by the so-called MEMS technology. However, key to their success will be a proof-of-concept in the clinic, which must demonstrate that the intradermal (nano)release of drugs and vaccines serve an unmet medical need. In this chapter, we discuss recently established MNA platform technologies and by means of a case study we assess novel opportunities for MNAs in drug and vaccine delivery arising from this novel skin interface.\u3c/p\u3

Hydrogel/poly-dimethylsiloxane hybrid bioreactor facilitating 3D cell culturing

The authors present a hydrogel/poly-dimethylsiloxane (PDMS) hybrid bioreactor. The bioreactor enables a low shear stress 3D culture by integrating a hydrogel as a barrier into a PDMS casing. The use of PDMS allows the reversible adhesion of the device to a commercially available microelectrode array. A two-step molding process facilitates this relatively simple, cost effective, and leakage-free add-on microculture system. Agarose (2%) is used as hydrogel barrier material and mass transport is evaluated by fluorescein isothiocyanate-albumin fluorescence under static conditions which yields a diffusion coefficient of average value of 2.2 × 10-7 cm 2 s-1 across the barrier. To validate our bioreactor for diffusion limited 3D cell culture, rat cortical cells were successfully cultured in Matrigel for 6 days. © 2013 American Vacuum Society

The need for physiological micro-nanofluidic systems of the brain

In this article, we review brain-on-a-chip models and associated underlying technologies. Micro-nanofluidic systems of the brain can utilize the entire spectrum of organoid technology. Notably, there is an urgent clinical need for a physiologically relevant microfluidic platform that can mimic the brain. Brain diseases affect millions of people worldwide, and this number will grow as the size of elderly population increases, thus making brain disease a serious public health problem. Brain disease modeling typically involves the use of in vivo rodent models, which is time consuming, resource intensive, and arguably unethical because many animals are required for a single study. Moreover, rodent models may not accurately predict human diseases, leading to erroneous results, thus rendering animal models poor predictors of human responses to treatment. Various clinical researchers have highlighted this issue, showing that initial physiological descriptions of animal models rarely encompass all the desired human features, including how closely the model captures what is observed in patients. Consequently, such animal models only mimic certain disease aspects, and they are often inadequate for studying how a certain molecule affects various aspects of a disease. Thus, there is a great need for the development of the brain-on-a-chip technology based on which a human brain model can be engineered by assembling cell lines to generate an organ-level model. To produce such a brain-on-a-chip device, selection of appropriate cells lines is critical because brain tissue consists of many different neuronal subtypes, including a plethora of supporting glial cell types. Additionally, cellular network bio-architecture significantly varies throughout different brain regions, forming complex structures and circuitries; this needs to be accounted for in the chip design process. Compartmentalized microenvironments can also be designed within the microphysiological cell culture system to fulfill advanced requirements of a given application. On-chip integration methods have already enabled advances in Parkinson's disease, Alzheimer's disease, and epilepsy modeling, which are discussed herein. In conclusion, for the brain model to be functional, combining engineered microsystems with stem cell (hiPSC) technology is specifically beneficial because hiPSCs can contribute to the complexity of tissue architecture based on their level of differentiation and thereby, biology itself

Nanoscale membrane actuator for in vitro mechano-stimuli responsive studies of neuronal cell networks on chip

\u3cp\u3eIn order to investigate the hypothesis that dynamic nanoscale stimuli can influence the functional response of the brain, in this paper we describe the development of a membrane actuator chip based on polydimethylsiloxane (PDMS) soft lithography. The chip exerts a local nanoscale mechanical load on an in vitro neuronal cell network by microfluidic pneumatic deformation of the membrane. The deformation provides a topographical change in the substrate as an input stimulus for the study of response functions of a neuronal cell network in vitro. Calcium ions (Ca\u3csup\u3e2+\u3c/sup\u3e) imaging within a neuronal cell network grown from dissociated cortical cells of the rat's brain used as a brain model indicates that a neural networks response can be provoked by means of our new method. This actuator chip provides a relatively mild and localised mechanical stimulus by means of a 2% elongation of the membrane's width during the application of a pressure pulse underneath the membrane using a microfluidic channel design. We found an average 50% increase of the intracellular Ca\u3csup\u3e2+\u3c/sup\u3e flux activity for 2D neuronal cell networks among 4 independent samples cultured on flat membranes. Additionally, we have proven the applicability of the actuator chip for networks on nanogrooved membranes by the observation of Ca\u3csup\u3e2+\u3c/sup\u3e traces and we also observed the Ca\u3csup\u3e2+\u3c/sup\u3e waves response upon stimulation in a three dimensional (3D) in vivo-like neuronal cell network using Matrigel on flat membranes. Hence, the chip potentially provides a novel technology platform for the in vitro modelling of brain tissues with topographically and 3D hydrogel-defined network architectures.\u3c/p\u3

Nanogroove-enhanced hydrogel scaffolds for 3D neuronal cell culture:an easy access brain-on-chip model

\u3cp\u3eIn order to better understand the brain and brain diseases, in vitro human brain models need to include not only a chemically and physically relevant microenvironment, but also structural network complexity. This complexity reflects the hierarchical architecture in brain tissue. Here, a method has been developed that adds complexity to a 3D cell culture by means of nanogrooved substrates. SH-SY5Y cells were grown on these nanogrooved substrates and covered with Matrigel, a hydrogel. To quantitatively analyze network behavior in 2D neuronal cell cultures, we previously developed an automated image-based screening method. We first investigated if this method was applicable to 3D primary rat brain cortical (CTX) cell cultures. Since the method was successfully applied to these pilot data, a proof of principle in a reductionist human brain cell model was attempted, using the SH-SY5Y cell line. The results showed that these cells also create an aligned network in the 3D microenvironment by maintaining a certain degree of guidance by the nanogrooved topography in the z-direction. These results indicate that nanogrooves enhance the structural complexity of 3D neuronal cell cultures for both CTX and human SH-SY5Y cultures, providing a basis for further development of an easy access brain-on-chip model.\u3c/p\u3

Investigating the interplay of lateral and height dimensions influencing neuronal processes on nanogrooves

\u3cp\u3eIn this work, nanogroove dimensions as a design input parameter for neuronal differentiation and neurite outgrowth in brain-on-a-chip (BOC) applications are investigated. Soft lithography in polydimethylsiloxane (PDMS) is used extensively in organ-on-a-chip applications to create environments for in vitro models. As such, here it is used to fabricate cell culture substrates with nanogrooved patterns. Using a newly developed analysis method, the effect of the nanogrooved, biomimetic PDMS substrates is compared with lateral and height variations within the nanometer range as measured by means of atomic force microscopy (AFM). PDMS culture substrates were replicated from a cyclic olefin copolymer template, which was fabricated either directly by thermal nanoimprinting from a jet and flash imprint lithography (J-FIL) resist pattern (process I) on a polished silicon wafer or via an intermediate reactive ion etched all-silicon mold (process II) that was fabricated by using the J-FIL resist pattern as in process I as a mask. To study the interplay between the lateral and height dimensions of nanogrooves on the differentiation process of SH-SY5Y cells, which are a well-established model for neuronal cells that form networks in culture, the authors first characterized the feature sizes of the PDMS substrates received from both processes by AFM. On average, nanogrooved patterns from process I had a 1.8 ± 1.1% decrease in pattern period, a 15.5 ± 12.2% increase in ridge width compared to the designed dimensions, and a height of 95.3 ± 10.6 nm. Nanogrooved patterns for process II had a 1.7 ± 1.7% decrease in pattern period, a 43.1 ± 33.2% increase in ridge width, and a height of 118.8 ± 13.6 nm. Subsequently, they demonstrated that neurite outgrowth alignment was particularly strong if the pattern period was 600 nm or 1000 nm with the additional constraint for these patterns that the ridge width is <0.4 times the pattern period. Increasing pattern height increased the fraction of differentiated cells within the cell culture and increased neurite length, but had no direct impact on outgrowth alignment. This study forms the basis for optimization in the bottom-up engineering of neuronal network architecture, for which specific patterns can be selected to assist in neuronal cell differentiation and direct neurite growth and alignment. Such organized neuronal networks can aid in the design of in vitro assay systems for BOC applications by improving biological response readouts and providing a better understanding of the relationship between form and function of a neuronal network.\u3c/p\u3

Microneedle array electrode for human EEG recording

Microneedle array electrodes for EEG significantly reduce the mounting time, particularly by circumvention of the need for skin preparation by scrubbing. We designed a new replication process for numerous types of microneedle arrays. Here, polymer microneedle array electrodes with 64 microneedles, in a nested 4×4 array, positioned on a circular disk of 10 mm diameter were fabricated and characterized. Needles have a length of 320 µm with a diameter of 100 µm. The DC-resistance of Ag-coated microneedle array electrodes on the skin is of the order of 150 kO. Using electrolyte gel this value decreases at least by a factor of 10. The pilot measurements on a healthy volunteer show excellent signal-to-noise ratios. According to conventional electrodes also Ag/AgCl instead of Ag only was used to coat the microneedle array. Both coatings, either with or without gel, certified for EEG recordings. © 2009 Springer Berlin Heidelberg

Single cell trapping by capillary pumping using NOA81 replica moulded stencils

\u3cp\u3eIn this contribution, we demonstrate that the optical adhesive NOA81 (Norland Products Inc.) can be used to replicate optically transparent single cell microsieve structures with exquisite resolution, enabling the fabrication of cheap stencils for single cell trapping applications by the combination of replica moulding and laser micromachining. In addition, we demonstrate an interesting capillary pumping mechanism for gently loading single neuronal cells which eliminates the need for equipment such as pumps and syringes. We demonstrate that capillary pumping through a microsieve generates gentle cell trapping velocities (<13.3 μm/s), enabling reproducible cell trapping efficiencies of 80% with high cell survival rates (90% over 1 week of culture) and facilitating the formation of spatially standardized neuronal networks.\u3c/p\u3