A Light-Curable and Tunable Extracellular Matrix Hydrogel for In Situ Suture-Free Corneal Repair.

Corneal injuries are a major cause of blindness worldwide. To restore corneal integrity and clarity, there is a need for regenerative bio-integrating materials for in-situ repair and replacement of corneal tissue. Here, we introduce Light-curable COrnea Matrix (LC-COMatrix), a tunable material derived from decellularized porcine cornea extracellular matrix containing un-denatured collagen and sulfated glycosaminoglycans. It is a functionalized hydrogel with proper swelling behavior, biodegradation, and viscosity that can be cross-linked in situ with visible light, providing significantly enhanced biomechanical strength, stability, and adhesiveness. Cross-linked LC-COMatrix strongly adheres to human corneas ex vivo and effectively closes full-thickness corneal perforations with tissue loss. Likewise, in vivo, LC-COMatrix seals large corneal perforations, replaces partial-corneal stromal defects and bio-integrates into the tissue in rabbit models. LC-COMatrix is a natural ready-to-apply bio-integrating adhesive that is representative of native corneal matrix with potential applications in corneal and ocular surgeries.

Engineering a 3D human intracranial aneurysm model using liquid-assisted injection molding and tuned hydrogels.

Physiologically relevant intracranial aneurysm (IA) models are crucially required to facilitate testing treatment options for IA. Herein, we report the development of a new in vitro tissue-engineered platform, which recapitulates the microenvironment, structure, and cellular complexity of native human IA. A new modified liquid-assisted injection molding technique was developed to fabricate a three-dimensional hollow IA model with clinically relevant IA dimensions within a mechanically tuned Gelatin Methacryloyl (GelMA) hydrogel. An endothelium lining was created inside the IA model by culturing human umbilical vein endothelial cells over pre-cultured human brain vascular smooth muscle cells. These cellularized IA models were subjected to medium perfusion at flow rates between 6.3 and 15.75 mL/min for inducing biomimetic vessel wall shear stress (10-25 dyn/cm2) to the cells for ten days. Both cell types maintained their secretome profiles and showed more than 96% viability, demonstrating the biocompatibility of the hydrogel during perfusion cell culture at such flow rates. Based on the characterized viscoelastic properties of the GelMA hydrogel and with the aid of a fluid-structure interaction model, the capability of the IA model in predicting the response of the IA to different fluid flow profiles was mathematically shown. With physiologically relevant behavior, our developed in vitro human IA model could allow researchers to better understand the pathophysiology and treatment of IA. STATEMENT OF SIGNIFICANCE: A three-dimensional intracranial aneurysm (IA) tissue model recapitulating the microenvironment, structure, and cellular complexity of native human IA was developed. • An endothelium lining was created inside the IA model over pre-cultured human brain vascular smooth muscle cells over at least 10-day successful culture. • The cells maintained their secretome profiles, demonstrating the biocompatibility of hydrogel during a long-term perfusion cell culture. • The IA model showed its capability in predicting the response of IA to different fluid flow profiles. • The cells in the vessel region behaved differently from cells in the aneurysm region due to alteration in hemodynamic shear stress. • The IA model could allow researchers to better understand the pathophysiology and treatment options of IA.

Tensile Viscoelastic Properties of the Sclera after Glycosaminoglycan Depletion.

PURPOSE: Fibrillar collagen network and glycosaminoglycans (GAGs) are the primary components of extracellular matrix (ECM) of the sclera. The main goal of this study was to investigate the possible structural roles of GAGs in the scleral tensile properties as a function of preconditioning and displacement rate. METHODS: Four-step uniaxial stress-relaxation tests were used for characterizing the viscoelastic tensile response of the posterior porcine sclera with and without enzymatic GAG removal. The scleral strips were divided into different groups based on the displacement rate and the presence or absence of a preconditioning step in the loading protocol. The groups were (1) displacement rate of 0.2 mm/min without preconditioning, (2) displacement rate of 1 mm/min without preconditioning, (3) displacement rate of 0.2 mm/min with preconditioning, and (4) displacement rate of 1 mm/min with preconditioning. The peak stress, equilibrium stress, and the equilibrium elastic modulus were calculated for all specimens and compared against each other. RESULTS: Increasing the displacement rate from 0.2 mm/min to 1.0 mm/min was found to cause an insignificant change in the equilibrium stress and equilibrium elastic modulus of porcine scleral strips. Removal of GAGs resulted in an overall stiffer tensile behavior independent of the displacement rate in samples that were not preconditioned (P < .05). The behavior of preconditioned samples with and without GAG removal was not significantly different from each other. CONCLUSIONS: The experimental measurements of the present study showed that GAGs play an important role in the mechanical properties of the posterior porcine sclera. Furthermore, using a preconditioning step in the uniaxial testing protocol resulted in not being able to identify any significant difference in the tensile behavior of GAG depleted and normal scleral strips.

Regional Differences in the Glycosaminoglycan Role in Porcine Scleral Hydration and Mechanical Behavior.

Purpose: This study characterized the role of glycosaminoglycans (GAGs) in the hydration, thickness, and biomechanical properties of posterior and anterior porcine sclera. Methods: The scleral discs and strips were obtained from the anterior and posterior parts of porcine eyes, and their initial hydration and thickness were measured. The anterior and posterior scleral discs were used to show the efficacy of the GAG removal protocol by quantifying their GAG content. The strips were divided into three groups of PBS treatment, buffer treatment, and enzyme treatment in order to assess the effects of different treatment procedures on the thickness, hydration, and viscoelastic properties of the samples. The mechanical properties of the strips were determined by performing uniaxial tensile stress relaxation experiments. Results: It was found that the control and buffer groups had insignificant differences in all measured quantities. The samples from the posterior region had a significantly larger GAG content and thickness in comparison with those from anterior region; however, there was an insignificant difference in their hydration. The GAG depletion process decreased the hydration of both anterior and posterior samples significantly (P < 0.05). Furthermore, the mechanical tests showed that the removal of GAGs resulted in stiffer mechanical behavior in both anterior and posterior samples (P < 0.05). In particular, the peak stress and equilibrium stress were significantly larger for the strips in the enzyme treatment group. Conclusions: GAGs and their interaction with the collagen network are important in defining the hydration and mechanical properties of both posterior and anterior sclera.

Hydration related changes in tensile response of posterior porcine sclera.

It has been shown that there exists significance dependence between hydration and biomechanical properties of hydrated tissues such as cornea. The primary purpose of this study was to determine hydration effects on mechanical properties of sclera. Scleral strips, dissected from the posterior part of pig eyes along the superior-inferior direction, were divided into four hydration groups by first drying them and then soaking them in PBS until their hydration reached to 75%, 100%, 150%, and 200%. The strips were subjected to ten consecutive cycles of loading and unloading up to 1 MPa. The response of samples at the tenth cycle was used to compute the tangent modulus, maximum strain, and hysteresis as a function of hydration. The experiments were done in oil in order to prevent hydration changes during the mechanical tests. The mechanical response of strips right after dissection, control group, was also measured. In general, significant softening of scleral strips was found with increasing hydration (p < 0.05). The stress-strain response of control group was between those of samples with hydration 150% and 200%. The experimental stress-strain data were successfully represented numerically with an exponential mathematical relation with R2 > 0.99. The present study showed that hydration would significantly alter the tensile response of scleral tissue. Thus, the hydration of scleral specimens during mechanical experimental measurements should be carefully controlled.

The contribution of sGAGs to stress-controlled tensile response of posterior porcine sclera.

Despite the significant progress in characterizing mechanical functions of individual scleral extracellular matrix (ECM) components, the biomechanical contribution of sulfated glycosaminoglycans (sGAGs) is still poorly understood. The primary purpose of this study was to determine the possible function of sGAGs in scleral mechanical response by characterizing the tensile behavior of normal and sGAG-depleted samples. We used chondroitinase ABC solution to remove sGAGs from scleral samples that were dissected from posterior porcine eyes. We performed biochemical analyses for assessing the efficacy of sGAG removal protocol. Furthermore, we conducted stress-controlled uniaxial tensile tests to characterize the influence of sGAG removal on mechanical properties of sclera. The tensile behavior of scleral strips right after dissection and after being soaked in buffer was also determined. Biochemical analyses confirmed that 18 hour incubation in 0.125 U/ml Chondroitinase ABC solution removed over 90% of chondroitin and dermatan sGAGs. No significant difference was observed in the thickness/hydration of samples because of enzyme- and buffer-treated samples. Furthermore, it was found that sGAG depletion did not significantly alter the tangent modulus, energy dissipation, and peak strain of posterior scleral strips. It was concluded that sGAGs did not influence the stress-controlled viscoelastic tensile response of sclera.

Dual effect of F-actin targeted carrier combined with antimitotic drug on aggressive colorectal cancer cytoskeleton: Allying dissimilar cell cytoskeleton disrupting mechanisms.

A recent approach to colon cancer therapy is to employ selective drugs with specific extra/intracellular sites of action. Alteration of cytoskeletal protein reorganization and, subsequently, to cellular biomechanical behaviour during cancer progression highly affects the cancer cell progress. Hence, cytoskeleton targeted drugs are an important class of cancer therapy agents. We have studied viscoelastic alteration of the human colon adenocarcinoma cell line, SW48, after treatment with a drug delivery system comprising chitosan as the carrier and albendazole as the microtubule-targeting agent (MTA). For the first time, we have evaluated the biomechanical characteristics of the cell line, using the micropipette aspiration (MA) method after treatment with drug delivery systems. Surprisingly, employing a chitosan-albendazole pair, in comparison with both neat materials, resulted in more significant change in the viscoelastic parameters of cells, including the elastic constants (K1 and K2) and the coefficient of viscosity (µ). This difference was more pronounced for cancer cells after 48h of the treatment. Microtubule and actin microfilament (F-actin) contents in the cell line were studied by immunofluorescent staining. Good agreement was observed between the mechanical characteristics results and microtubule/F-actin contents of the treated SW48 cell line, which declined after treatment. The results showed that chitosan affected F-actin more, while MTA was more effective for microtubules. Toxicity studies were performed against two cancer cell lines (SW48 and MCF10CA1h) and compared to normal cells, MCF10A. The results showed cancer selectiveness, safety of formulation, and enhanced anticancer efficacy of the CS/ABZ conjugate. This study suggests that employing such a suitable pair of drug-carriers with dissimilar sites of action, thus allying the different cell cytoskeleton disrupting mechanisms, may provide a more efficient cancer therapy approach.