Determining the Relationship Between Corneal Stiffening and Tissue Dehydration After Corneal Cross-Linking.

Purpose: To quantify corneal cross-linking (CXL)-induced stiffening via mechanical testing to estimate the impact of changes in hydration levels (H) and evaluate depth-dependent tissue hydration after CXL.

Methods: Eighty-three porcine corneal buttons were divided into three groups: Standard protocol CXL (S-CXL), accelerated CXL (A-CXL), and untreated (nonirradiated riboflavin-only) controls. Samples were hydrated or dehydrated to modulate H and dynamic mechanical analyzer compression tests were performed to measure Young's modulus (E).

Rapid in situ forming PEG hydrogels for mucosal drug delivery.

gelling polymeric biomaterials have proven useful as drug delivery vehicles to enable sustained release at sites of disease or injury. However, if delivered to mucosal tissues, such as the eyes, nose, gastrointestinal, and cervicovaginal tract, these gels must also possess the ability to adhere to an epithelium coated in mucus. Towards this end, we report a new rapid gelling polyethylene glycol-based hydrogel.

Network Viscoelasticity from Brillouin Spectroscopy.

Even though the physical nature of shear and longitudinal moduli are different, empirical correlations between them have been reported in several biological systems. This correlation is of fundamental interest and immense practical value in biomedicine due to the importance of the shear modulus and the possibility to map the longitudinal modulus at high-resolution with all-optical spectroscopy. We investigate the origin of such a correlation in hydrogels.

Controlled Release of a Therapeutic Peptide in Sprayable Surgical Sealant for Prevention of Postoperative Abdominal Adhesions.

Formation of asymmetric, rigid scar tissue known as surgical adhesions is caused by traumatic disruption of mesothelial-lined surfaces in surgery. A widely adopted prophylactic barrier material (Seprafilm) for the treatment of intra-abdominal adhesions is applied operatively as a pre-dried hydrogel sheet but has reduced translational efficacy due its brittle mechanical properties. Topically administered peritoneal dialysate (Icodextrin) and anti-inflammatory drugs have failed to prevent adhesions due to an uncontrolled release profile.

Phosphate Capture Enhancement Using Designed Iron Oxide-Based Nanostructures.

Phosphates in high concentrations are harmful pollutants for the environment, and new and cheap solutions are currently needed for phosphate removal from polluted liquid media. Iron oxide nanoparticles show a promising capacity for removing phosphates from polluted media and can be easily separated from polluted media under an external magnetic field. However, they have to display a high surface area allowing high removal pollutant capacity while preserving their magnetic properties.

Sprayable tissue adhesive with biodegradation tuned for prevention of postoperative abdominal adhesions.

Adhesions are dense, fibrous bridges that adjoin tissue surfaces due to uncontrolled inflammation following postoperative mesothelial injury. A widely used adhesion barrier material in Seprafilm often fails to prevent transverse scar tissue deposition because of its poor mechanical properties, rapid degradation profile, and difficulty in precise application. Solution blow spinning (SBS), a polymer fiber deposition technique, allows for the placement of in situ tissue-conforming and tissue-adherent scaffolds with exceptional mechanical properties.

Biodegradable, Tissue Adhesive Polyester Blends for Safe, Complete Wound Healing.

Pressure-sensitive adhesives typically used for bandages are nonbiodegradable, inhibiting healing, and may cause an allergic reaction. Here, we investigated the effect of biodegradable copolymers with promising thermomechanical properties on wound healing for their eventual use as biodegradable, biocompatible adhesives. Blends of low molecular weight (LMW) and high molecular weight (HMW) poly(lactide--caprolactone) (PLCL) are investigated as tissue adhesives in comparison to a clinical control.

Hybrid 3D Printing of Synthetic and Cell-Laden Bioinks for Shape Retaining Soft Tissue Grafts.

Despite recent advances in clinical procedures, the repair of soft tissue remains a reconstructive challenge. Current technologies such as synthetic implants and dermal flap autografting result in inefficient shape retention and unpredictable aesthetic outcomes. 3D printing, however, can be leveraged to produce superior soft tissue grafts that allow enhanced host integration and volume retention.

Pressure-Sensitive Tissue Adhesion and Biodegradation of Viscoelastic Polymer Blends.

Viscoelastic blends of biodegradable polyesters with low and high molecular weight distributions have remarkably strong adhesion (significantly greater than 1 N/cm) to soft, wet tissue. Those that transition from viscous flow to elastic, solidlike behavior at approximately 1 Hz demonstrate pressure-sensitivity yet also have sufficient elasticity for durable bonding to soft, wet tissue. The pressure-sensitive tissue adhesive (PSTA) blends produce increasingly stronger pull-apart adhesion in response to compressive pressure application, from 10 to 300 s.

Sprayable and biodegradable, intrinsically adhesive wound dressing with antimicrobial properties.

Conventional wound dressings are difficult to apply to large total body surface area (TBSA) wounds, as they typically are prefabricated, require a layer of adhesive coating for fixation, and need frequent replacement for entrapped exudate. Large TBSA wounds as well as orthopedic trauma and low-resource surgery also have a high risk of infection. In this report, a sprayable and intrinsically adhesive wound dressing loaded with antimicrobial silver is investigated that provides personalized fabrication with minimal patient contact.

Rapid and Tunable Method To Fabricate Angle-Independent and Transferable Structurally Colored Films.

The assembly of monodisperse particles into colloidal arrays that diffract visible light through constructive interference is of considerable interest due to their resilience against color fading. In particular, noniridescent structurally colored materials are promising as a means of coloration for paints, inks, cosmetics, and displays because their color is angle independent. A rapid and tunable assembly method for producing noniridescent structurally colored colloidal-based materials that are pliable after fabrication is described.

Structurally colored protease responsive nanoparticle hydrogels with degradation-directed assembly.

A tunable protease responsive nanoparticle hydrogel (PRNH) that demonstrates large non-iridescent color changes due to a degradation-directed assembly of nanoparticles is reported. Structurally colored composites are fabricated with silica particles, 4-arm poly(ethylene glycol) norbornene (4PEGN), and a proteolytically degradable peptide. When placed in a protease solution, the peptide crosslinks degrade causing electrostatic binding and adsorption of the polymer to the particle surface which leads to the assembly of particles into compact amorphous arrays with structural color.

Improving the adhesion, flexibility, and hemostatic efficacy of a sprayable polymer blend surgical sealant by incorporating silica particles.

Commercially available surgical sealants for internal use either lack sufficient adhesion or produce cytotoxicity. This work describes a surgical sealant based on a polymer blend of poly(lactic-co-glycolic acid) (PLGA) and poly(ethylene glycol) (PEG) that increases wet tissue adherence by incorporation of nano-to-microscale silica particles, without significantly affecting cell viability, biodegradation rate, or local inflammation. In functional studies, PLGA/PEG/silica composite sealants produce intestinal burst pressures that are comparable to cyanoacrylate glue (160 mmHg), ∼2 times greater than the non-composite sealant (59 mmHg), and ∼3 times greater than fibrin glue (49 mmHg).

Multistage Chemical Heating for Instrument-Free Biosensing.

Improving the portability of diagnostic medicine is crucial for alleviating global access-to-care deficiencies. This requires not only designing devices that are small and lightweight, but also autonomous and independent of electricity. Here, we present a strategy for conducting automated multistep diagnostic assays using chemically generated, passively regulated heat.

Spray-Processed Composites with High Conductivity and Elasticity.

Highly conductive elastic composites were constructed using multistep solution-based fabrication methods that included the deposition of a nonwoven polymer fiber mat through solution blow spinning and nanoparticle nucleation. High nanoparticle loading was achieved by introducing silver nanoparticles into the fiber spinning solution. The presence of the silver nanoparticles facilitates improved uptake of silver nanoparticle precursor in subsequent processing steps.

Zeolite-loaded alginate-chitosan hydrogel beads as a topical hemostat.

Hemorrhage is the leading cause of preventable death after a traumatic injury, and the largest contributor to loss of productive years of life. Hemostatic agents accelerate hemostasis and help control hemorrhage by concentrating coagulation factors, acting as procoagulants and/or interacting with erythrocytes and platelets. Hydrogel composites offer a platform for targeting both mechanical and biological hemostatic mechanisms.

A Review of the Fundamental Principles and Applications of Solution Blow Spinning.

Solution blow spinning (SBS) is a technique that can be used to deposit fibers in situ at low cost for a variety of applications, which include biomedical materials and flexible electronics. This review is intended to provide an overview of the basic principles and applications of SBS. We first describe a method for creating a spinnable polymer solution and stable polymer solution jet by manipulating parameters such as polymer concentration and gas pressure.

Solution blow spun polymer: A novel preclinical surgical sealant for bowel anastomoses.

Background: Solution blow spinning is a technique for depositing polymer fibers with promising potential use as a surgical sealant. This study assessed the feasibility and efficacy of solution blow spun polymer (BSP) for sealing bowel perforations in a mouse model of partial cecal transection. We then evaluated its use for reinforcing a surgical anastomosis in a preclinical piglet model.

Protein Adsorption on Chemically Modified Block Copolymer Nanodomains: Influence of Charge and Flow.

Understanding the interactions of biomacromolecules with nanoengineered surfaces is vital for assessing material biocompatibility. This study focuses on the dynamics of protein adsorption on nanopatterned block copolymers (BCPs). Poly(styrene)-block-poly(1,2-butadiene) BCPs functionalized with an acid, amine, amide, or captopril moieties were processed to produce nanopatterned films.

Rapid fabrication of poly(DL-lactide) nanofiber scaffolds with tunable degradation for tissue engineering applications by air-brushing.

Polymer nanofiber based materials have been widely investigated for use as tissue engineering scaffolds. While promising, these materials are typically fabricated through techniques that require significant time or cost. Here we report a rapid and cost effective air-brushing method for fabricating nanofiber scaffolds using a simple handheld apparatus, compressed air, and a polymer solution.

Biodegradable-Polymer-Blend-Based Surgical Sealant with Body-Temperature-Mediated Adhesion.

The development of practical and efficient surgical sealants has the propensity to improve operational outcomes. A biodegradable polymer blend is fabricated as a nonwoven fiber mat in situ. After direct deposition onto the tissue of interest, the material transitions from a fiber mat to a film.

Enzyme Induced Stiffening of Nanoparticle-Hydrogel Composites with Structural Color.

The passive monitoring of biological environments by soft materials has a variety of nanobiotechnology applications; however, invoking distinct transitions in geometric, mechanical or optical properties remains a prevalent design challenge. We demonstrate here that close-packed nanoparticle-hydrogel composites can progress through a substantial shift in such properties by the use of a chemical-to-physical cross-link transition mediated by the catalytic activity of different proteases. Catalytic cleavage of the original hydrogel network structure initiates the self-assembled formation of a secondary, physically cross-linked network, causing a 1200% increase in storage modulus.