Biomechanical properties of porcine meniscus as determined via AFM: Effect of region, compartment and anisotropy.

The meniscus is a fibrocartilaginous tissue that plays an essential role in load transmission, lubrication, and stabilization of the knee. Loss of meniscus function, through degeneration or trauma, can lead to osteoarthritis in the underlying articular cartilage. To perform its crucial function, the meniscus extracellular matrix has a particular organization, including collagen fiber bundles running circumferentially, allowing the tissue to withstand tensile hoop stresses developed during axial loading.

Characterization of Trabecular Meshwork Mechanical Property Modulation After Application of Lipids.

Treatment of lipids endogenous to the aqueous humor of the eye could serve as a potential therapy to slow the progression of glaucoma. Herein, we describe the method to treat trabecular meshwork samples in vitro with lipids and characterize changes in the samples' stiffness.

Performance of islets of Langerhans conformally coated via an emulsion cross-linking method in diabetic rodents and nonhuman primates.

Polyethylene glycol (PEG)-based conformal coating (CC) encapsulation of transplanted islets is a promising β cell replacement therapy for the treatment of type 1 diabetes without chronic immunosuppression because it minimizes capsule thickness, graft volume, and insulin secretion delay. However, we show here that our original CC method, the direct method, requiring exposure of islets to low pH levels and inclusion of viscosity enhancers during coating, severely affected the viability, scalability, and biocompatibility of CC islets in nonhuman primate preclinical models of type 1 diabetes. We therefore developed and validated in vitro and in vivo, in several small- and large-animal models of type 1 diabetes, an augmented CC method-emulsion method-that achieves hydrogel CCs around islets at physiological pH for improved cytocompatibility, with PEG hydrogels for increased biocompatibility and with fivefold increase in encapsulation throughput for enhanced scalability.

Measuring the effects of postmortem time and age on mouse lens elasticity using atomic force microscopy.

The mouse lens is frequently used both in vivo and ex vivo in ophthalmic research to model conditions affecting the human lens, such as presbyopia. The mouse lens has a delicate structure which is prone to damage and biomechanical changes both before and after extraction from the whole globe. When not properly controlled for, these changes can confound the biomechanical analysis of mouse lenses.

Porous Silicon Nanoparticles Embedded in Poly(lactic--glycolic acid) Nanofiber Scaffolds Deliver Neurotrophic Payloads to Enhance Neuronal Growth.

Scaffolds made from biocompatible polymers provide physical cues to direct the extension of neurites and to encourage repair of damaged nerves. The inclusion of neurotrophic payloads in these scaffolds can substantially enhance regrowth and repair processes. However, many promising neurotrophic candidates are excluded from this approach due to incompatibilities with the polymer or with the polymer processing conditions.

Characterization of Polyethylene Glycol-Reinforced Alginate Microcapsules for Mechanically Stable Cell Immunoisolation.

Islet transplantation within mechanically stable microcapsules offers the promise of long-term diabetes reversal without chronic immunosuppression. Reinforcing the ionically gelled network of alginate (ALG) hydrogels with covalently linked polyethylene glycol (PEG) may create hybrid structures with desirable mechanical properties. This report describes the fabrication of hybrid PEG-ALG interpenetrating polymer networks and the investigation of microcapsule swelling, surface modulus, rheology, compression, and permeability.

Age-dependency of molecular diffusion in the human anterior lens capsule assessed using fluorescence recovery after photobleaching.

Purpose: To quantify the partition coefficient and the diffusion coefficient of metal-carrier proteins in the human lens capsule as a function of age.

Methods: Whole lenses from human donors were incubated overnight in a solution of fluorescently labeled transferrin, albumin, or ceruloplasmin. In the central plane of the capsule thickness, fluorescence recovery after photobleaching (FRAP) experiments were conducted to measure the diffusion of the protein within the lens capsule.

Micromorphology analysis of the anterior human lens capsule.

Purpose: This study aimed to quantify the three-dimensional micromorphology of the surface of the human lens capsule as a function of age.

Methods: Imaging experiments were conducted on whole human lenses received from eight human cadavers (donor age range: 30-88 years). Imaging was performed with an atomic force microscope (AFM) in contact mode in fluid.

Corneal elasticity after oxygen enriched high intensity corneal cross linking assessed using atomic force microscopy.

The purpose of this study was to assess anterior and mid corneal stromal elasticity after high intensity (HI) corneal cross linking (CXL), with and without oxygen (O) enrichment, and compare these results to conventional CXL. Experiments were performed on 25 pairs of human cadaver eyes, divided into four different groups. Group 1 included corneas that did not receive treatment and served as controls; Group 2 included corneas that received conventional CXL treatment (Dresden Protocol: corneal epithelial debridement, 30 min of riboflavin pretreatment followed by 30 min of exposure to 3 mW/cm of ultraviolet light); Group 3 included corneas that received HI CXL treatment (corneal epithelial debridement, 30 min of riboflavin pretreatment followed by 3 min of exposure to 30mW/cm of ultraviolet light); and Group 4 included corneas that received the same treatment as Group 3, except that they were enriched with oxygen (4 L per minute pure O gas stream) during ultraviolet irradiation.

Assessment of micro-mechanical variations in experimental arteriovenous fistulae using atomic force microscopy.

Purpose: This study presents a method to quantify micro-stiffness variations in experimental arteriovenous fistulae (AVF).

Methods: AVF created by anastomosing the superficial epigastric vein to the femoral artery in Sprague-Dawley rats were allowed to remodel for 21 days before being harvested and preserved in culture medium. A custom atomic force microscope was used to measure microvascular stiffness (Young's modulus) in three areas of the AVF: the inflow artery, the juxta-anastomotic area, and the outflow vein.

Multiscale Investigation of the Depth-Dependent Mechanical Anisotropy of the Human Corneal Stroma.

Purpose: To investigate the depth-dependent mechanical anisotropy of the human corneal stroma at the tissue (stroma) and molecular (collagen) level by using atomic force microscopy (AFM).

Methods: Eleven human donor corneas were dissected at different stromal depths by using a microkeratome. Mechanical measurements were performed in 15% dextran on the surface of the exposed stroma of each sample by using a custom-built AFM in force spectroscopy mode using both microspherical (38-μm diameter) and nanoconical (10-nm radius of curvature) indenters at 2-μm/s and 15-μm/s indentation rates.

Corneal stromal elasticity and viscoelasticity assessed by atomic force microscopy after different cross linking protocols.

The purpose of this study was to evaluate elasticity and viscoelasticity in the anterior and deeper stromal regions of the cornea after cross linking with three different protocols using atomic force microscopy (AFM) through indentation. A total of 40 porcine corneas were used in this study and were divided into 4 groups (10 corneas per group): control (no treatment), Dresden (corneal epithelial debridement, riboflavin pretreatment for 30 min and a 3mw/cm(2) for 30 min UVA irradiation), accelerated (corneal epithelial debridement, riboflavin pretreatment for 30 min and a 30mw/cm(2) for 3 min UVA irradiation), and genipin (corneal epithelial debridement and submersion of anterior surface in a 1% genipin solution for 4 h). Elasticity and viscoelasticity were quantified using AFM through indentation for all corneas, for the anterior stroma and at a depth of 200 μm.

Lens capsule structure assessed with atomic force microscopy.

Purpose: To image the ultrastructure of the anterior lens capsule at the nanoscale level using atomic force microscopy (AFM).

Methods: Experiments were performed on anterior lens capsules maintained in their in situ location surrounding the lens from six human cadavers (donor age range: 44-88 years), four cynomolgus monkeys (Macaca fascicularis age range: 4.83-8.

Impact of Hydration Media on Ex Vivo Corneal Elasticity Measurements.

Objectives: To determine the effect of hydration media on ex vivo corneal elasticity.

Methods: Experiments were conducted on 40 porcine eyes retrieved from an abattoir (10 eyes each for phosphate-buffered saline (PBS), balanced salt solution, Optisol, 15% dextran). The epithelium was removed, and the cornea was excised with an intact scleral rim and placed in 20% dextran overnight to restore its physiological thickness.

Progerin expression disrupts critical adult stem cell functions involved in tissue repair.

Vascular disease is one of the leading causes of death worldwide. Vascular repair, essential for tissue maintenance, is critically reduced during vascular disease and aging. Efficient vascular repair requires functional adult stem cells unimpaired by aging or mutation.

Fractal analysis of AFM images of the surface of Bowman's membrane of the human cornea.

The objective of this study is to further investigate the ultrastructural details of the surface of Bowman's membrane of the human cornea, using atomic force microscopy (AFM) images. One representative image acquired of Bowman's membrane of a human cornea was investigated. The three-dimensional (3-D) surface of the sample was imaged using AFM in contact mode, while the sample was completely submerged in optisol solution.

Surface quality of human corneal lenticules after SMILE assessed using environmental scanning electron microscopy.

Purpose: To assess the cut quality of the anterior and posterior surfaces of intrastromal refractive lenticules removed during small incision lenticule extraction (SMILE).

Methods: The VisuMax femtosecond laser (500 kHz; Carl Zeiss Meditec, Dublin, CA) was used to perform SMILE on 8 eyes of 5 individuals to correct only myopia (no cylinder). The cut energy index was 26 (equivalent to an energy of 130 nJ) with a 2.

Anterior and posterior corneal stroma elasticity after corneal collagen crosslinking treatment.

The purpose of this project was to assess anterior and posterior corneal stromal elasticity after corneal collagen cross linking (CXL) treatment in human cadaver eyes using Atomic Force Microscopy (AFM) through indentation. Twenty four human cadaver eyes (12 pairs) were included in this study and divided into 2 groups (6 pairs per group). In both groups, the left eye (OS) served as a control (no riboflavin or CXL treatment was performed) and the right eye (OD) underwent CXL treatment (30 min of riboflavin pretreatment followed by 30 min of exposure to 3 mW/cm(2) of ultraviolet light).

Anterior and posterior corneal stroma elasticity assessed using nanoindentation.

Corneal biomechanics is an essential parameter for developing diagnostic and treatment methods of corneal-related diseases. It is widely accepted that corneal mechanical strength stems from the stroma's collagenous composition. However, more comprehensive insight into the mechanical properties within the stroma is needed to improve current corneal diagnostic and treatment techniques.

Quality of corneal lamellar cuts quantified using atomic force microscopy.

Purpose: To quantify the cut quality of lamellar dissections made with the femtosecond laser using atomic force microscopy (AFM).

Setting: Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, USA.

Design: Experimental study.

The effect of nicotine on the mechanical properties of mesenchymal stem cells.

PURPOSE: To measure the elasticity of the nucleus and cytoplasm of human mesenchymal stem cells (MSCs) as well as changes brought about by exposure to nicotine in vitro. METHODS: MSCs were synchronized to the G(0) stage of the cell cycle through serum deprivation techniques. The cells were then treated with medium containing nicotine (0.

Primate lens capsule elasticity assessed using Atomic Force Microscopy.

The purpose of this project is to measure the elasticity of the human and non-human primate lens capsule at the microscopic scale using Atomic Force Microscopy (AFM). Elasticity measurements were performed using AFM on the excised anterior lens capsule from 9 cynomolgus monkey (5.9-8.

Refractive power and biometric properties of the nonhuman primate isolated crystalline lens.

Purpose. To characterize the age dependence of shape, refractive power, and refractive index of isolated lenses from nonhuman primates. Methods.