A Rheological Study on the Effect of Tethering Pro- and Anti-Inflammatory Cytokines into Hydrogels on Human Mesenchymal Stem Cell Migration, Degradation, and Morphology.

Polymer-peptide hydrogels are being designed as implantable materials that deliver human mesenchymal stem cells (hMSCs) to treat wounds. Most wounds can progress through the healing process without intervention. During the normal healing process, cytokines are released from the wound to create a concentration gradient, which causes directed cell migration from the native niche to the wound site. Our work takes inspiration from this process and uniformly tethers cytokines into the scaffold to measure changes in cell-mediated degradation and motility. This is the first step in designing cytokine concentration gradients into the material to direct cell migration. We measure changes in rheological properties, encapsulated cell-mediated pericellular degradation and migration in a hydrogel scaffold with covalently tethered cytokines, either tumor necrosis factor-α (TNF-α) or transforming growth factor-ß (TGF-ß). TNF-α is expressed in early stages of wound healing causing an inflammatory response. TGF-ß is released in later stages of wound healing causing an anti-inflammatory response in the surrounding tissue. Both cytokines cause directed cell migration. We measure no statistically significant difference in modulus or the critical relaxation exponent when tethering either cytokine in the polymeric network without encapsulated hMSCs. This indicates that the scaffold structure and rheology is unchanged by the addition of tethered cytokines. Increases in hMSC motility, morphology and cell-mediated degradation are measured using a combination of multiple particle tracking microrheology (MPT) and live-cell imaging in hydrogels with tethered cytokines. We measure that tethering TNF-α into the hydrogel increases cellular remodeling on earlier days postencapsulation and tethering TGF-ß into the scaffold increases cellular remodeling on later days. We measure tethering either TGF-ß or TNF-α enhances cell stretching and, subsequently, migration. This work provides rheological characterization that can be used to design new materials that present chemical cues in the pericellular region to direct cell migration.

Characterizing Phase Transitions of Microfibrillated Cellulose Induced by Anionic and Cationic Surfactants.

Rheological modifiers are used to tune rheology or induce phase transitions of products. Microfibrillated cellulose (MFC), a renewable material, has the potential to be used for rheological modification. However, the lack of studies on the evolution in rheological properties and structure during its phase transitions has prevented MFC from being added to consumer, fabric, and home care products. In this work, we characterize surface-oxidized MFC (OMFC), a negatively charged colloidal rod suspension. We measure the rheological properties and structure of OMFC during sol-gel phase transitions induced by either anionic or cationic surfactant using multiple particle tracking microrheology (MPT). MPT tracks the Brownian motion of fluorescent probe particles embedded in a sample, which is related to the sample's rheological properties. Using MPT, we measure that OMFC gelation evolution is dependent on the charge of the surfactant that induces the phase transition. OMFC gelation is gradual in anionic surfactant. In cationic surfactant, gelation is rapid followed by length scale-dependent colloidal fiber rearrangement. Initial OMFC concentration is directly related to how tightly associated the network is at the phase transition, with an increase in concentration resulting in a more tightly associated network with smaller pores. Bulk rheology measures that OMFC forms a stiffer structure but yields at lower strains in cationic surfactant than in anionic surfactant. This study characterizes the role of surfactant in inducing phase transitions, which can be used as a guide for designing future products.

Characterizing rheological properties and microstructure of thioester networks during degradation.

Covalent adaptable networks are designed for applications including cell and drug delivery and tissue regeneration. These applications require network degradation at physiological conditions and on a physiological timescale with microstructures that can: (1) support, protect and deliver encapsulated cells or molecules and (2) provide structure to surrounding tissue. Due to this, the evolving microstructure and rheological properties during scaffold degradation must be characterized. In this work, we characterize degradation of covalent adaptable poly(ethylene glycol) (PEG)-thioester networks with different amounts of excess thiol. Networks are formed between PEG-thiol and PEG-thioester norbornene using photopolymerization. These networks are adaptable because of a thioester exchange reaction that takes place in the presence of excess thiol. We measure degradation of PEG-thioester networks with L-cysteine using multiple particle tracking microrheology (MPT). MPT measures the Brownian motion of fluorescent probe particles embedded in a material and relates this motion to rheological properties. Using time-cure superposition (TCS), we characterize the microstructure of these networks at the gel-sol phase transition by calculating the critical relaxation exponent, n, for each network with different amounts of excess thiol. Based on the measured n values, networks formed with 0% and 50% excess thiol are tightly cross-linked and elastic in nature. While networks formed with 100% excess are similar to ideal, percolated networks, which have equal viscous and elastic components. MPT measurements during degradation of these networks also measure a non-monotonic increase in probe motility. We hypothesize that this is network rearrangement near the phase transition. We then measure macroscopic material properties including the equilibrium modulus and stress relaxation. We measure a trend in bulk network properties that agrees with the values of n. Elastic modulus and stress relaxation measurements show that networks with 50% excess thiol are more elastic compared to the other two networks. As the amount of excess thiol is increased from 0% to 50%, the networks become more elastic. Further increasing excess thiol to 100% reduces the elastically effective cross-links. We hypothesize that these properties are due to network non-idealities, resulting in networks with 50% excess thiol that are more elastic. This work characterizes dynamic rheological properties during degradation, which mimics processes that could occur during implantation. This work provides information that can be used in the future design of implantable materials enabling both the rheological properties and timescale of degradation to be specified.

Measuring human mesenchymal stem cell remodeling in hydrogels with a step-change in elastic modulus.

Human mesenchymal stem cells (hMSCs) are instrumental in the wound healing process. They migrate to wounds from their native niche in response to chemical signals released during the inflammatory phase of healing. At the wound, hMSCs downregulate inflammation and regulate tissue regeneration. Delivering additional hMSCs to wounds using cell-laden implantable hydrogels has the potential to improve healing outcomes and restart healing in chronic wounds. For these materials to be effective, cells must migrate from the scaffold into the native tissue. This requires cells to traverse a step-change in material properties at the implant-tissue interface. Migration of cells in material with highly varying properties is not well characterized. We measure 3D encapsulated hMSC migration and remodeling in a well-characterized hydrogel with a step-change in stiffness. This cell-degradable hydrogel is composed of 4-arm poly(ethylene glycol)-norbornene cross-linked with an enzymatically-degradable peptide. The scaffold is made with two halves of different stiffnesses separated by an interface where stiffness changes rapidly. We characterize changes in structure and rheology of the pericellular region using multiple particle tracking microrheology (MPT). MPT measures Brownian motion of embedded particles and relates it to material rheology. We measure more remodeling in the soft region of the hydrogel than the stiff region on day 1 post-encapsulation and similar remodeling everywhere on day 6. In the interface region, we measure hMSC-mediated remodeling along the interface and migration towards the stiff side of the scaffold. These results can improve materials designed for cell delivery from implants to a wound to enhance healing.

Veterinary and Pharmacy Students' Expectations Before and Experiences After Participating in an Interdisciplinary Access to Care Veterinary Clinic, WisCARES.

This pilot survey study describes student expectations and experiences at WisCARES, a low-cost veterinary medical teaching clinic where students from multiple disciplines collaborate. We hypothesized that prior to the workday, students would describe different expectations of working in an interdisciplinary access to care clinic than what they ultimately experienced. We surveyed 62 students from the School of Veterinary Medicine (46) and pharmacy (16) who spent a clinic day at WisCARES. Before introductory rounds, students completed a short survey consisting of four open-ended questions about their learning expectations; at the end of the day, they reviewed their initial responses and added what they actually learned. Qualitative information was categorized and analyzed using descriptive statistics. Thirteen major themes emerged: diversity, confidence, communication, case lead/case management, financial experience, helping people, teamwork, technical skills, inter-professional experience, mentoring, non-specific positive regard, appreciation for resources, and rounds. Students reported improved confidence in managing and leading cases with specific positive outcomes in communicating with clients, particularly regarding leading financial conversations. Developing greater insight into diversity was a common theme expressed in students' expectations but was less frequently noted as an end-of-day outcome. Veterinary students less frequently described the value of the inter-professional environment and collaboration, but this was a major theme noted among pharmacy students. Student feedback was positive overall. The current study is useful in identifying areas for improving collaborative instruction and access to care professional student learning opportunities.

Correlation of Bulk Degradation and Molecular Release from Enzymatically Degradable Polymeric Hydrogels.

In this work, we establish a quantitative correlation between molecular release and material degradation. We characterize a radical-initiated photopolymerized hydrogel and base-initiated Michael addition-polymerized hydrogel, which form gels through distinct crosslinking reactions. Both scaffolds use the same degradable peptide crosslinker, which enables them to be degraded through the same enzymatic degradation reaction. A fluorescently labeled poly(ethylene glycol) molecule is chemically conjugated into the scaffold and is released during enzymatic degradation. Real-time changes in scaffold rheological properties during degradation are measured using bulk rheology. Molecular release is measured by quantifying the change in fluorescence in the incubation liquid and the hydrogel scaffold. A complicating factor, previously described in the literature, is that shear may cause increased crosslinking, resulting in an increase in the storage modulus after initiation of degradation, which changes release profiles by limiting the initial release of molecules. Therefore, we also test the hypothesis that shear induces additional crosslinking in degrading hydrogel scaffolds. To determine whether shear changes rheological properties during scaffold degradation, enzymatic degradation is characterized using bulk rheology as materials undergo continuous or minimal shear. To determine the effect of shear on molecular release, shear is induced by shaking the material during incubation. Release is characterized from scaffolds that are incubated with continuous or without shaking. We determine that shear does not make a difference in scaffold degradation or release regardless of the gelation reaction. Instead, we determine that the type of hydrogel crosslinking reaction greatly affects both material degradation and molecular release. A hydrogel crosslinking by base-initiated Michael addition does undergo further crosslinking at the start of degradation. We correlate release with enzymatic degradation for both scaffolds. We determine that the material storage modulus is indirectly correlated with release during degradation. These results indicate that rheological characterization is a useful tool to characterize and predict the release of molecules from degrading hydrogels.

Droplet-Based Microfluidic Tool to Quantify Viscosity of Concentrating Protein Solutions.

PURPOSE: Measurement of the viscosity of concentrated protein solutions is vital for the manufacture and delivery of protein therapeutics. Conventional methods for viscosity measurements require large solution volumes, creating a severe limitation during the early stage of protein development. The goal of this work is to develop a robust technique that requires minimal sample. METHODS: In this work, a droplet-based microfluidic device is developed to quantify the viscosity of protein solutions while concentrating in micrometer-scale droplets. The technique requires only microliters of sample. The corresponding viscosity is characterized by multiple particle tracking microrheology (MPT). RESULTS: We show that the viscosities quantified in the microfluidic device are consistent with macroscopic results measured by a conventional rheometer for poly(ethylene) glycol (PEG) solutions. The technique was further applied to quantify viscosities of well-studied lysozyme and bovine serum albumin (BSA) solutions. Comparison to both macroscopic measurements and models (Krieger-Dougherty model) demonstrate the validity of the approach. CONCLUSION: The droplet-based microfluidic device provides accurate quantitative values of viscosity over a range of concentrations for protein solutions with small sample volumes (~ µL) and high compositional resolution. This device will be extended to study the effect of different excipients and other additives on the viscosity of protein solutions.

The Nuts and Bolts of a Successful Non-Narcotic Perioperative Enhanced Recovery After Surgery Protocol.

BACKGROUND: Enhanced recovery after surgery (ERAS) protocols are widely utilized approaches to perioperative care that advocate preoperative counseling, multimodal perioperative medication management, and early postoperative mobilization to improve post-surgical patient outcomes and satisfaction. OBJECTIVES: The authors aimed to elucidate the mechanism by which each medication utilized in the senior author's ERAS protocol acts, determine the efficacy of this protocol in postoperative pain management, and reveal other factors that may play a role in patients' degree of postoperative pain. METHODS: A literature review was performed on the medications utilized in the senior author's ERAS protocol. Evidence from the author's previous study on the efficacy of this regimen and anecdotal evidence regarding the psychological component of pain was also compiled. RESULTS: There is evidence that an ERAS protocol is as effective if not more effective than regimens involving opioid medications in management of postoperative pain. These medications act synergistically to block perception of pain by multiple pathways, while minimizing adverse effects that may be associated with high doses of a single medication and are affordable for both the patient and the surgeon. CONCLUSIONS: ERAS protocols effectively manage postoperative pain while avoiding the adverse effects associated with opioid medications. Although an emphasis has often been placed on the medications involved in various protocols and avoidance of opioid medications, appropriate counseling on patients' expectations concerning postoperative "pain" or discomfort and a systemic shift in the approach to perioperative pain are perhaps the most important components to holistic non-narcotic postoperative care.

Determining How Human Mesenchymal Stem Cells Change Their Degradation Strategy in Response to Microenvironmental Stiffness.

During the wound healing process, human mesenchymal stem cells (hMSCs) are recruited to the injury where they regulate inflammation and initiate healing and tissue regeneration. To aid in healing, synthetic cell-laden hydrogel scaffolds are being designed to deliver additional hMSCs to wounds to enhance or restart the healing process. These scaffolds are being designed to mimic native tissue environments, which include physical cues, such as scaffold stiffness. In this work, we focus on how the initial scaffold stiffness hMSCs are encapsulated in changes cell-mediated remodeling and degradation and motility. To do this, we encapsulate hMSCs in a well-defined synthetic hydrogel scaffold that recapitulates aspects of the native extracellular matrix (ECM). We then characterize cell-mediated degradation in the pericellular region as a function of initial microenvironmental stiffness. Our hydrogel consists of a 4-arm poly(ethylene glycol) (PEG) end-functionalized with norbornene which is chemically cross-linked with a matrix metalloproteinase (MMP) degradable peptide sequence. This peptide sequence is cleaved by hMSC-secreted MMPs. The hydrogel elastic modulus is varied from 80 to 2400 Pa by changing the concentration of the peptide cross-linker. We use multiple particle tracking microrheology (MPT) to characterize the spatiotemporal cell-mediated degradation in the pericellular region. In MPT, fluorescently labeled particles are embedded in the material, and their Brownian motion is measured. We measure an increase in cell-mediated degradation and remodeling as the post-encapsulation time increases. MPT also measures changes in the degradation profile in the pericellular region as hydrogel stiffness is increased. We hypothesize that the change in the degradation profile is due to a change in the amount and type of molecules secreted by hMSCs. We also measure a significant decrease in cell speed as hydrogel stiffness increases due to the increased physical barrier that needs to be degraded to enable motility. These measurements increase our understanding of the rheological changes in the pericellular region in different physical microenvironments which could lead to better design of implantable biomaterials for cell delivery to wounded areas.

Microrheological characterization of covalent adaptable hydrogel degradation in response to temporal pH changes that mimic the gastrointestinal tract.

Covalent adaptable hydrogels (CAHs) reversibly adapt their structure in response to external stimuli, emerging as a new platform for biological applications. Due to the unique and complex nature of these materials, a characterization technique is needed to measure the rheology of these CAHs in biological processes. µ2rheology, microrheology in a microfluidic device, is a technique that can fully characterize real-time CAH degradation in a changing environment, such as the pH environment of the GI tract. This characterization will enable design and tailoring of these materials for controlled and targeted oral drug delivery. Using µ2rheology, we can exchange the fluid environment without sample loss and measure the change in CAH rheological properties. We show degradation kinetics and material property evolution are independent of degradation history. However, the initial cross-link density at each pH exchange can be decreased by degradation history which decreases the time for the CAH to degrade to the gel-sol transition. These results indicate that CAH degradation can be tuned by changing the initial material properties by varying polymer concentration and ratio of functional groups. We also show that µ2rheology will enable the design of new dynamic materials for targeted drug delivery by enabling these materials to be characterized and tailored in vitro.

Microrheological characterization of covalent adaptable hydrogels for applications in oral delivery.

The feasibility of a covalent adaptable hydrogel (CAH) as an oral delivery platform is explored using µ2rheology, microrheology in a microfluidic device. CAH degradation is initiated by physiologically relevant pHs, including incubation at a single pH and consecutively at different pHs. At a single pH, we determine CAH degradation can be tuned by changing the pH, which can be exploited for controlled release. We calculate the critical relaxation exponent, which defines the gel-sol transition and is independent of the degradation pH. We mimic the changing pH environment through part of the gastrointestinal tract (pH 4.3 to 7.4 or pH 7.4 to 4.3) in our microfluidic device. We determine that dynamic material property evolution is consistent with degradation at a single pH. However, the time scale of degradation is reduced by the history of degradation. These investigations inform the design of this material as a new vehicle for targeted delivery.

Nitrosonium Reactivity of (NHC)Copper(I) Sulfide Complexes.

This study examines the reactivity of a series of copper(I) sulfide complexes stabilized by the expanded-ring N-heterocyclic carbene (NHC) 1,3-bis(2,6-diisopropylphenyl)-4,5,6,7-tetrahydro-1,3-diazepin-2-ylidene (7Dipp) toward the nitrosonium ion (NO+). 7Dipp is shown to support neutral sulfide- and disulfide-bridged dicopper(I) complexes, as well as mononuclear copper(I) hydrosulfide. The addition of NO+ to each of these results in the formation of NHC-supported copper(I) cations and elemental sulfur. Reduction of copper(I) to copper(0) is observed upon reaction of NO+ with dicopper(I) sulfide or disulfide, whereas ammonium ion formation is observed upon reaction of copper(I) hydrosulfide with NO+. Ammonium ion formation is likewise observed upon reaction of NO+ with (7Dipp)copper(I) hydride.

Speech Outcomes After LeFort I Advancement Among Cleft Lip and Palate Patients.

BACKGROUND: Velopharyngeal insufficiency (VPI) results from incomplete closure of the velopharyngeal (VP) sphincter with oral pressure consonants during speech. Maxillary hypoplasia is common among cleft children and often requires LeFort I advancement. This results in anterior movement of the soft palate with the bony maxillary segment. Consequently, the size of the VP sphincter is increased and may result postoperative VPI or worsening of prior VPI. To better counsel our patients and their families of the risk of VPI after LeFort I advancement, we chose to evaluate our own cohort. METHODS: We conducted an institutional review board-approved prospective review of all cleft children presenting to Texas Children's Hospital who underwent LeFort I advancement after previous palatoplasty between 2013 and 2016 in a three-surgeon, consecutive patient series. Data collected included age, sex, ethnicity, cleft type, prior secondary speech surgery, presence of preoperative fistula, planned distance of advancement, orthognathic surgery performed, and any concurrent procedures performed. Primary outcomes measured included preoperative and postoperative VP function and hypernasality as measured by a certified speech pathologist. RESULTS: Velopharyngeal function was unchanged in 67% of our cohort after LeFort I advancement. Of those patients, 83% had evidence of VPI preoperatively, and 17% had normal speech preoperatively. Twenty-two percent of the patients displayed worsening VP function after surgery, and 6% displayed evidence of improvement. Velopharyngeal function was unable to be assessed in 6% of patients. Nasality ratings worsened in 39% of patients, were unchanged in 39%, and improved in 22%. Of the patients with incompetent VP function after surgery, 50% already received or are currently scheduled for secondary speech surgery, 25% declined secondary surgery, and 25% are pending scheduling. CONCLUSIONS: Although VP function remains unchanged in a majority of patients after LeFort I advancement, VPI should be carefully screened for after surgery. If detected, secondary operations to correct speech should be strongly considered.

Characterizing the dynamic rheology in the pericellular region by human mesenchymal stem cell re-engineering in PEG-peptide hydrogel scaffolds.

During wound healing, human mesenchymal stem cells (hMSCs) migrate to injuries to regulate inflammation and coordinate tissue regeneration. To enable migration, hMSCs re-engineer the extracellular matrix rheology. Our work determines the correlation between cell engineered rheology and motility. We encapsulate hMSCs in a cell-degradable peptide-polymeric hydrogel and characterize the change in rheological properties in the pericellular region using multiple particle tracking microrheology. Previous studies determined that pericellular rheology is correlated with motility. Additionally, hMSCs re-engineer their microenvironment by regulating cell-secreted enzyme, matrix metallopro-teinases (MMPs), activity by also secreting their inhibitors, tissue inhibitors of metalloproteinases (TIMPs). We independently inhibit TIMPs and measure two different degradation profiles, reaction-diffusion and reverse reaction-diffusion. These profiles are correlated with cell spreading, speed and motility type. We model scaffold degradation using Michaelis-Menten kinetics, finding a decrease in kinetics between joint and independent TIMP inhibition. hMSCs ability to regulate microenvironmental remodeling and motility could be exploited in design of new materials that deliver hMSCs to wounds to enhance healing.

Syndromic Multisuture Craniosynostosis With Associated Anterior Segment Dysgenesis, Optic Nerve Hypoplasia, and Congenital Glaucoma.

Patients with craniosynostosis with subnormal vision due to papilledema and/or exposure-related corneal decompensation are well documented in the literature; however, there is only a single prior documented case of vision compromise secondary to anterior segment dysgenesis and glaucoma in this patient population. This report highlights a case of syndromic craniosynostosis with advanced corneal decompensation and anterior segment dysgenesis that was masked and ultimately delayed the diagnosis of congenital glaucoma.

Multiple particle tracking microrheology measured using bi-disperse probe diameters.

Multiple particle tracking microrheology (MPT) is a powerful tool for quantitatively characterizing rheological properties of soft matter. Traditionally, MPT uses a single particle size to characterize rheological properties. But in complex systems, MPT measurements with a single size particle can characterize distinct properties that are linked to the materials' length scale dependent structure. By varying the size of probes, MPT can measure the properties associated with different length scales within a material. We develop a technique to simultaneously track a bi-disperse population of probe particles. 0.5 and 2 µm particles are embedded in the same sample and these particle populations are tracked separately using a brightness-based squared radius of gyration, Rg2. Bi-disperse MPT is validated by measuring the viscosity of glycerol samples at varying concentrations. Bi-disperse MPT measurements agree well with literature values. This technique then characterizes a homogeneous poly(ethylene glycol)-acrylate:poly(ethylene glycol)-dithiol gelation. The critical relaxation exponent and critical gelation time are consistent and agree with previous measurements using a single particle. Finally, degradation of a heterogeneous hydrogenated castor oil colloidal gel is characterized. The two particle sizes measure a different value of the critical relaxation exponent, indicating that they are probing different structures. Analysis of material heterogeneity shows measured heterogeneity is dependent on probe size indicating that each particle is measuring rheological evolution of a length scale dependent structure. Overall, bi-disperse MPT increases the amount of information gained in a single measurement, enabling more complete characterization of complex systems that range from consumer care products to biological materials.

Rheological characterization of dynamic remodeling of the pericellular region by human mesenchymal stem cell-secreted enzymes in well-defined synthetic hydrogel scaffolds.

Human mesenchymal stem cells (hMSCs) dynamically remodel their microenvironment during basic processes, such as migration and differentiation. Migration requires extracellular matrix invasion, necessitating dynamic cell-material interactions. Understanding these interactions is critical to advancing materials designs that harness and manipulate these processes for applications including wound healing and tissue regeneration. In this work, we encapsulate hMSCs in a cell-degradable poly(ethylene glycol)-peptide hydrogel to determine how cell-secreted enzymes, specifically matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs), create unique pericellular microenvironments. Using multiple particle tracking microrheology (MPT), we characterize spatio-temporal rheological properties in the pericellular region during cell-mediated remodeling. In MPT, the thermal motion of probes embedded in the network is measured. A newly designed sample chamber that limits probe drift during degradation and minimizes high value antibody volumes required for cell treatments enables MPT characterization. Previous MPT measurements around hMSCs show that directly around the cell the scaffold remains intact with the cross-link density decreasing as distance from the cell increases. This degradation profile suggests that hMSCs are simultaneously secreting TIMPs, which are inactivating MMPs through MMP-TIMP complexes. By neutralizing TIMPs using antibodies, we characterize the changes in matrix degradation. TIMP inhibited hMSCs create a reaction-diffusion type degradation profile where MMPs are actively degrading the matrix immediately after secretion. In this profile, the cross-link density increases with increasing distance from the cell. This change in material properties also increases the speed of migration. This simple treatment could increase delivery of hMSCs to injuries to aid wound healing and tissue regeneration.

Measuring dynamic cell-material interactions and remodeling during 3D human mesenchymal stem cell migration in hydrogels.

Biomaterials that mimic aspects of the extracellular matrix by presenting a 3D microenvironment that cells can locally degrade and remodel are finding increased applications as wound-healing matrices, tissue engineering scaffolds, and even substrates for stem cell expansion. In vivo, cells do not simply reside in a static microenvironment, but instead, they dynamically reengineer their surroundings. For example, cells secrete proteases that degrade extracellular components, attach to the matrix through adhesive sites, and can exert traction forces on the local matrix, causing its spatial reorganization. Although biomaterials scaffolds provide initially well-defined microenvironments for 3D culture of cells, less is known about the changes that occur over time, especially local matrix remodeling that can play an integral role in directing cell behavior. Here, we use microrheology as a quantitative tool to characterize dynamic cellular remodeling of peptide-functionalized poly(ethylene glycol) (PEG) hydrogels that degrade in response to cell-secreted matrix metalloproteinases (MMPs). This technique allows measurement of spatial changes in material properties during migration of encapsulated cells and has a sensitivity that identifies regions where cells simply adhere to the matrix, as well as the extent of local cell remodeling of the material through MMP-mediated degradation. Collectively, these microrheological measurements provide insight into microscopic, cellular manipulation of the pericellular region that gives rise to macroscopic tracks created in scaffolds by migrating cells. This quantitative and predictable information should benefit the design of improved biomaterial scaffolds for medically relevant applications.

Presentation of a Rare Lobulated Tongue Anomaly.

The presence of a bilobed tongue is a rare congenital malformation. There are multiple reports of a bifid anterior lobe; however, a case with complete separation of isolated anterior and posterior lobes has not been previously described. We report the case of a 2-year-old male, who presented with a V-shaped mandible and glossoptosis in the setting of respiratory distress and difficulty feeding, incidentally found to have a bilobed tongue with independent anterior and posterior lobes.

Quantifying the dynamic transition of hydrogenated castor oil gels measured via multiple particle tracking microrheology.

Rheological modifiers are essential ingredients in commercial materials that exploit facile and repeatable phase transitions. Although rheological modifiers are used to change flow behavior or quiescent stability, the complex properties of particulate gels during dilution is not well studied. We characterize a dynamically evolving colloidal gel, hydrogenated castor oil (HCO), a naturally sourced material, used in consumer products. This HCO scaffold consists of fibrous colloids, a surfactant (linear alkylbenzene sulfonate) and water. The gel undergoes critical transitions, degradation and formation, in response to an osmotic pressure gradient. Multiple particle tracking microrheology (MPT) measures the evolving material properties. In MPT, fluorescent probe particles are embedded into the sample and Brownian motion is measured. MPT data are analyzed using time-cure superposition, identifying critical transition times and critical relaxation exponents for degradation and formation where tc,deg = 102.5 min, ndeg = 0.77 ± 0.09, tc,for = 31.9 min, and nfor = 0.94 ± 0.11, respectively. During degradation and formation HCO gels evolve heterogeneously, this heterogeneity is characterized spatially and temporally. Heterogeneity of the gel is quantified by comparing variances of single particle van Hove correlation functions using an F-test with a 95% confidence interval. HCO transitions have rheological heterogeneous microenvironments that are homogeneously distributed throughout the field of view. Although HCO gels do evolve heterogeneously, this work determines that these heterogeneities do not significantly change traditional MPT measurements but the analysis techniques developed provide additional information on the unique heterogeneous scaffold microenvironments. This creates a toolbox that can be widely applied to other scaffolds during dynamic transitions.