Adhering wet conducting polymers on diverse substrates

Adhering wet conducting polymers on diverse substrates

Conducting polymers serve as an interface between electrodes and biological organisms in bioelectronic devices. Some examples are poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), polypyrrole (PPy), and polyaniline (PAni) which have favorable electrical and mechanical properties and biocompatibility. However in a wet physiological environment, weak and unstable adhesion occurs leading to interfacial failures. In this article on Science Advances journal, Dr. Xuanhe Zhao and his team spanning from MIT in USA to JSR Corporation in Japan and Jiangxi Science and Technology Normal University in China present a successful method to achieve strong adhesion of various conducting polymers on substrates in wet physiological environments. They introduced a hydrophilic polymer adhesive layer of only a few nanometers thick but strongly bonds wet conducting polymers to various substrates. Furthermore, a variety of fabrication methods can be used to produce this adhesion layer.

The team start with a smooth substrate functionalized with primary amine groups. This provides an enhanced interfacial adhesion between the substrate and adhesive layer via covalent bonds and/or electrostatic interaction. Next, the adhesive layer is applied via spin coating, spray coating or dip coating. A layer of conducting polymer is applied on top of the adhesive layer which then results in a swelling of the adhesive layer due to polymer precursors diffusing into it. A schematic of the process is seen in the image above.

Tests conducted to measure the mechanical and electrical integrity of the adhesive layer on the substrate include lap-shear tests, standard four-point probe, electrochemical impedance spectroscopy analysis and tensile tests. The CellScale UStretch performed tensile tests to determine the effect of the adhesive layer on the conducting polymer under varying thickness of the adhesive layer. Images below show the test set-up and results.

To read the full article, click here: https://doi.org/10.1126/sciadv.aay5394

To read more about Dr. Zhao’s research, click here: http://meche.mit.edu/people/faculty/ZHAOX@MIT.EDU

To read about a lap-shear test done with the UStretch, click here.

Aerogel Beads for Removal of Copper

Aerogel Beads for Removal of Copper

Heavy metals are serious pollutants in wastewater that are discharged to the environment.  Although there are various methods to remove them, the most common method is commercial powder absorbents.  These have poor recyclability (which can lead to secondary pollution), low removal efficiency, and high cost.  Dr. Michael Tam and his team from the University of Waterloo have proposed to use cellulose-based aerogels as ideal absorbents for copper.  Aerogels are porous materials with high surface area and absorption capacity while cellulose is an environmentally friendly compound used to prepare aerogels.  However, this cellulose aerogel needs to be enhanced by chemical crosslinking to improve the wet mechanical strength and removal rate.  The team at UW used (3-glycidyloxypropyl) trimethoxysilane (GPTMS) to cross-link polyethylenimine (PEI) onto cellulose nanofibrils (CNF).  An illustration of the process is shown above.

To characterize the formed aerogel beads, an array of tests was conducted including Fourier-transform infrared spectroscopy (to detect peaks of the covalent bonds), SEM (to visualize the morphology of the beads) and compressive stress-strain measurements (to analyze the mechanical stability during adsorption).  Individual beads underwent parallel plate compression testing using the CellScale MicroTester and the resulting stress-strain curves were plotted.  A video of these tests and the resulting strain-strain graphs at different strain levels are shown below.

To read the full article, click here: https://doi.org/10.1016/j.cej.2020.124821

To read more about Dr. Tam’s research, click here: http://chemeng.uwaterloo.ca/mtam/

To read about a similar compression testing with pullalan microbeads, click here.

Development of Scaffolds with Adjusted Stiffness

Development of Scaffolds with Adjusted Stiffness

New in vitro models using human cells are increasingly being used to replace animal testing for drug development. Freshly isolated human hepatocytes are ideal in predicting liver toxicity in these models, although they are highly limited and tend to lose their metabolic function after a long time in culture. Researchers therefore turn to liver cell lines as an alternative while they determine ways of extending and improving the hepatocytes metabolic activity while in culture. One proposed method is to allow hepatocytes to interact with their surrounding matrix, such as a scaffold. A 3D culture system can sustain metabolic activity and improve cell nutrients’ supply. Also, by varying the stiffness of the scaffold, metabolic activity of hepatocytes can be altered. In this study, Dr. Andreas Nüssler and his team at the Siegfried Weller Institute for Trauma Medical Research in Eberhard Karls University developed a scaffold that mimicked the stiffness of healthy and fibrotic livers. A coating of fetal calf serum (FCS) on the scaffold was studied as well for cell adherence.

To measure the stiffness of the scaffolds, the team used the CellScale MicroTester in a parallel-plate compression test mode. 4 different scaffold prototypes with different cryogel compositions were tested and compared to literature data of healthy, fibrotic and cirrothic liver tissue. The graph below shows the results from the test.

An interesting aspect of their study was the effect of scaffold pre-incubation on cell adherence. From the image at the top, it was found that a longer pre-incubation period (of up to 10 days) of the scaffold generated increased cell adherence significantly.

To read the full article, click here: https://doi.org/10.3390/jfb11010017

To read more about Dr. Nüssler‘s research, click here: https://www.bgu-tuebingen.de/forschung/siegfried-weller-institut-fuer-unfallmedizinische-forschung/

To read about a multiparametric analysis of tissue spheroids, click here.

Multiparametric Analysis of Tissue Spheroids

Multiparametric Analysis of Tissue Spheroids

Tissue spheroids (TS) are being increasingly recognized as a powerful tool to create 3D human tissues. This complex cell and matrix composition is formed without scaffolds and can recapitulate the architecture and functional characteristics of native tissue. TS is extremely attractive as an alternative to animal testing in drug discovery and cancer research, however the fabrication of TS is widely diverse and does not follow a protocol that tracks spheroids size, growth and morphology over time. Here, Dr. Elena Bulanova and her team at the Laboratory for Biotechnology Research 3D Bioprinting Solutions in Russia has presented a straightforward procedure for fabricating and characterizing TS with defined properties and uniform predictable geometry. Her solution applies to different cell types and uses non-adhesive technology.
In their comprehensive study,  they have established that different cell types contributed to different growth patterns, where diameter and roundness parameters were tracked over time up to 9 days. TS morphology and viability were also found to be cell-type specific. Using the CellScale MicroTester, the team could evaluate the mechanical properties of TS and discovered them to vary significantly depending on cell type. The image below shows the setup of the MicroTester for the experiment and the graph below shows the Elastic Modulus of TS for different cell types and maturation time.

 

To read the full article, click here: https://doi.org/10.1002/biot.201900217

To read more about Dr. Bulanova’s research, click here: https://scholar.google.com/citations?user=V8gGRS0AAAAJ&hl=en

To read about mechanical testing of miniaturized needle arrays, click here.

Promoting Maturation of hiPSC-derived Cardiomyocytes with Re-entrant Waves

Promoting Maturation of hiPSC-derived Cardiomyocytes with Re-entrant Waves

Human-induced pluripotent stem cell (hiPSC) derived cardiomyocytes present themselves as an abundant resource for tissue engineering, drug screening and regenerative-medicine applications. However, they are available in an immature state, mimicking poorly the physiology of adult human cardiomyocytes. There are methods to increase the maturation and function of hiPSC-derived cardiomyocytes, although each of them presents shortfalls such as heavy metal poisoning and difficulty in mass stimulation. Dr. Li Liu, Y Sawa and their team and her team from Osaka University Graduate School of Medicine has published in Nature journal an article about their success in creating a platform capable of promoting rapid formation of hiPSC-derived cardiomyocytes into 3D self-organized tissue rings (SOTRs). In addition, they constructed a mathematical model to characterize the long-term behavior of the reentrant waves (ReW) within the cardiac tissue. The image above shows the schematics and actual images of the SOTRs from their experiment.

The SOTRs created were studied for beating frequency and ReW speed in relation to the ring diameter. They were also analyzed for specific gene expression, Ca2+ handling properties, oxygen-consumption rate and contractile force. To measure the contractile force, the team used the CellScale MicroTester in a 3-point bending test setup while immersed in a temperature-controlled water bath. The graph below shows the maximum contraction force at 2 different ReWs.

To read the full article, click here: https://doi.org/10.1038/s42003-020-0853-0

To read more about Dr. Liu’s research, click here: http://www.dma.jim.osaka-u.ac.jp/view?l=en&u=10008971&f1=I&f2=I90&sm=field&sl=en&sp=1

To read about another publication with the CellScale MicroTester, click here.

A Wireless Smart Bandage with Miniaturized Needle Arrays

A Wireless Smart Bandage with Miniaturized Needle Arrays

Patients with type II diabetes experience chronic wounds, a condition where wounds fail to self-heal after 3 months. Physiological processes leading to wound healing such as vascularization are disrupted and biofilms form on the wound bed that are resistant to topical antibiotics treatment. Dr. Ali Tamayol and his team from the University of Nebraska-Lincoln published a study in the journal of Advanced Functional Materials about a wearable and programmable bandage that can deliver vital drugs into the deeper layers of the wound bed, past the biofilm. They achieve this with miniaturized needle arrays (MNAs) that induce minimal pain and inflammation compared to other invasive methods. The programmable portion allows a physician to remotely administer therapeutics as needed.

To fabricate the MNAs, the team used a multimaterial 3D printer that created hollow MNAs out of a biocompatible resin. Needle spacings, needle lengths, base sizes and opening diameters could be customized for various wound types. To investigate the mechanical properties of the printed needles (more specifically its breakage force), compression force testing with the CellScale UniVert was done at 200N. This same instrument was also employed to investigate penetration and retraction force of the MNAs on pig skin (see image below), as well as the bonding strength of the MNA island to a PDMS substrate holding microchannels for drug delivery.

To read the full article about their design, fabrication and tests, click here: https://doi.org/10.1002/adfm.201905544
To read more about Dr. Tamayol’s research, click here: http://tamayol-lab.weebly.com/

To read about a low-cost, pilot-scale, melt-processing system, click here.