CellScale User Publication Highlight: Axial Torsion of the Annulus Fibrosus

CellScale User Publication Highlight: Axial Torsion of the Annulus Fibrosus

The intervertebral disc (IVD) is made of an inner nucleus pulposus and a surrounding annulus fibrosus (AF). IVD herniation occurs when the inner nucleus pulposus breaks through the layers of AF, and is associated with both spinal rotation and repetitive flexion. However an explanation of the details of tissue mechanism in play is lacking. Dr Diane Gregory and Maxine Harvey-Burgess from Wilfrid Laurier University aim to bridge this knowledge gap using cow tail IVDs subjected to static axial torsion and tensile testing. Their study also included histological staining that clearly showed torsion resulted in disruption of the AF.

The key finding of this work was that axial rotation did not affect the adhesion between layers of the AF but rather disrupted the layers themselves. Therefore, this work indicates that annular layer disruption is one of the key mechanisms of increased risk of herniation with axial torsion.  Although there were limitations in their research such as how bovine IVD may have different torsional distribution than the human IVD, this paper shed light on AF microstructures under mechanical stress and how they eventually lead to IVD herniation. 

In their experiments, the CellScale BioTester and UStretch were employed for biaxial and uniaxial tests respectively. The image above shows a T-peel test and a tension test of the specimen, along with tissue sample locations within the IVD.

Read the full journal article here: https://doi.org/10.1097/BRS.0000000000002803

Read about Dr Ethier’s research here: https://www.wlu.ca/academics/faculties/faculty-of-science/faculty-profiles/diane-gregory/index.html

To read about compressive mechanical properties of rat and pig optic nerve head, click here.

 

CellScale’s Promotion to NEW countries

CellScale’s Promotion to NEW countries

CellScale Biomaterials Testing is proud to have sold its equipment to over 30 countries worldwide, thanks to our global network of distributors. Our BioTester can be found in Singapore, US and Australia, the MicroTester in UK and India, and the MechanoCulture instruments in Poland, China and Canada. We are now pleased to offer this one-time discount to any NEW countries we have never sold to: 10% off. This offer is valid till the end of 2019.

 

And here is the list of the countries carrying CellScale’s instruments:

Australia
Austria
Belgium
Brazil
Canada
Chile
China
Czech Republic
Denmark
Finland
France
Germany
India
Ireland
Israel
Italy
Japan
Korea
Mexico
Netherlands
Poland
Qatar
Russia
Singapore
Spain
South Africa
Sweden
Switzerland
Turkey
UAE
United Kingdom
United States

If you have any questions or would like to know more about our instruments, please feel free to contact us at info@cellscale.com.

CellScale User Publication Highlight: Compressive Mechanical Properties of Rat and Pig Optic Nerve Head

CellScale User Publication Highlight: Compressive Mechanical Properties of Rat and Pig Optic Nerve Head

Glaucoma is an optic neuropathy that can cause irreversible blindness because of the progressive damage and loss of retinal ganglion cells (RGCs). At elevated intraocular pressure (IOP), optic nerve head (ONH) tissues experience high deformations which may lead to tissue damage, restriction of blood flow and nutrient supply, pathological changes and direct RGC axonal damage. There is thus a need for a thorough understanding of the biomechanics of ONH and its mechanical strain under IOP. Dr. C. Ross Ethier and his team from Georgia Institute of Technology performed their study on rat and pig ONH tissues, opting for compression instead of the commonly published tension data as compression is the main mode of deformation in vivo at IOP.

Using the CellScale MicroTester parallel plate compression test mode and the neo-Hookean hyperelastic model, material constant C values were obtained. The team varied the strain percentage and number of compression loading cycles for both rat and pig ONH. Results gathered from their tests (shown in the graphs below) can greatly facilitate the development of animal-specific computational models and in vitro platforms to study glaucoma.

Read the full journal article here: https://doi.org/10.1016/j.jbiomech.2019.06.014

Read about Dr Ethier’s research here: https://ethier.gatech.edu/

To read about the biomechanical impact of localized corneal cross-linking, click here.

 

CellScale User Publication Highlight: Effect of Halloysite Addition on the Material Properties of Chitosan-Halloysite Hydrogel Composites

CellScale User Publication Highlight: Effect of Halloysite Addition on the Material Properties of Chitosan-Halloysite Hydrogel Composites

Chitosan (CS) is a naturally derived hydrogel that has potential as an implantable drug delivery system. Although it possesses quality traits such as non-toxicity, a lack of immunogenicity and the ability to assemble a tissue-specific extracellular matrix, it is inherently weak in its mechanical properties. Incorporating nanoparticles in CS have been shown to significantly increase strength, tensile modulus, hardness and toughness of the resulting polymer. Dr. David Mills and Yangyang Luo from Lousiana Tech University decided to investigate the impact of different concentration of CS and Halloysite nanotubes (HNTs) on not just the mechanical properties, but cellular behaviors as well.

There are several interesting discoveries discussed in this paper. A higher CS concentration produced a more uniform bead shape and drug release capability. It also formed hydrogels with smaller pore sizes. In their degradation study, HNTs were shown to have no significant effect on CS degradation. As a drug delivery system, the CS-HNTs hybrid hydrogel had a more sustained ability in drug release compared to pure CS, due to its better mechanical properties.

Mechanical properties such as tensile strength were measured with a CellScale UniVert. The team was able to derive the Young’s Modulus of the hydrogels by knowing the measured values of tensile strength and elongation. The graphs above and below show the Young’s Modulus of various hydrogels at various concentrations of CS and HNTs. 

Read the full journal article here: https://doi.org/10.3390/gels5030040

Read about Dr Mills’ research here: https://millsbiomorph.wixsite.com/biomorphlab

To read about the inclusion of chloride salt and nano-particles in methacrylated gelatin for bioprinting, click here.

 

CellScale User Publication Highlight: 3D Bioprinting with Methacrylated Gelatin Upon Inclusion of Chroride Salt and Nano-Particles

CellScale User Publication Highlight: 3D Bioprinting with Methacrylated Gelatin Upon Inclusion of Chroride Salt and Nano-Particles

3D bioprinting has significantly gained popularity in recent years as a mean to create custom structural scaffolds that are hierarchical and biologically functional. Optimizing the bioink involves targeting characteristics such as viscosity, crosslinking capabilities, stability under physiological conditions (pH, temperature etc.) and resistance to proteolytic degradation. In this study, Dr. Patricia Comeau and Dr. Thomas Willett from the University of Waterloo varied the levels of chloride salts (NaCl and CaCl2) and hydroxyapatite nano-particles (nHA) in methacrylated gelatin (GelMA), a common organic matrix in bioink due to its inherent bioactivity and the ability to have their physiochemical properties easily tailored. These neutral salts were selected based on hypotheses that CaCl2 would increase viscosity and improve photo-polymerization of the solution, while NaCl would have a lesser impact due to the limited bonding interactions it has as a monovalent ion. The inclusion of nHA acts as a reinforcing mineral particle phase within the protein matrix, working to enhance the mechanical properties of the gel. 

The paper analyzes viscosity and UV curing of GelMA-based solutions and inks, their swelling in MilliQ distilled water, and dynamic mechanical analysis of the cast hydrogel specimens. The CellScale UniVert was used in a cyclic sinusoidal loading mode between 0 and 8% compressive strain at a frequency of 0.01Hz to determine the dynamic modulus, storage modulus and loss modulus of the hydrogels.
Graphs below show dynamic modulus of GelMA-based hydrogels with varying concentrations of Ca2+, Na+, and nHA included.
 
Dr Willett and team have achieved in this paper 3D printed hydrogels with dynamic modulus matching that of articular cartilage. This was a first for a GelMA-based composite system. 

Read the full journal article here: https://doi.org/10.1002/mame.201900142

Read about Dr Willett’s and Dr Comeau’s research here: https://uwaterloo.ca/waterloo-composite-biomaterial-systems-lab/

To read about a bioink blend for rotary 3D bioprinting of vascular constructs, click here.

 

CellScale User Publication Highlight: A Comparison Between Thin Films and Inverse Double Network Bilayers for Oral Drug Delivery Systems

CellScale User Publication Highlight: A Comparison Between Thin Films and Inverse Double Network Bilayers for Oral Drug Delivery Systems

An inverse double network (IDN) hydrogel is a setup of a neutral hydrogel layer with a polyelectrolyte polymer layer adhered to it. This bilayer design allows for changes in volume when either layer responds differently to stimulus (pH, temperature, light, etc.). The structure may fold, twist or bend, and controlling these features is important for oral drug delivery applications. Dr. Teja Guda and his team from the University of Texas at San Antonio report in this paper, a strategy to improve the stability of the polyelectrolyte layer in bilayer hydrogels. They studied the hydrogel’s ability to bend when the pH changes, compared conventional thin film coated bilayers against their formed IDNs, and characterized drug release profile using the antibiotic Vancomycin.

One interesting test that was performed in this research was mucoadhesion testing. Mucoadhesion is simply the adhesion between two materials, one of which is a mucosal surface (NCBI). It is vital for a drug delivery system to possess mucoadhesion properties so that the drugs will be better absorbed by the body through mucosal surfaces present in our mouth, stomach or gut lining. In this study, the team used porcine small intestine tissues affixed on polyvinyl chloride sheets on which the bilayer samples were attached. The samples and the porcine segments then underwent a lap shear test using the CellScale UStretch. The graph below illustrates detachment force required in PBS of 3 samples: polyvinyl alcohol, IDN and thin film.

 

Read the full journal article here: http://dx.doi.org/10.1177/0885328219861614

Read about Dr Guda’s research here: http://engineering.utsa.edu/biomedical/team/teja-guda-ph-d/

To read about a similar research on shape-changing hydrogels to stimuli, click here.