Synthetic hydrogels as blood clot mimicking wound healing materials

Mechanical properties of clot made from human and bovine whole blood differ significantly

Thromboembolism - that is, clot formation and the subsequent fragmentation of clot - is a leading cause of death worldwide. Clots' mechanical properties are critical determinants of both the embolization process and the pathophysiological consequences thereof. Thus, understanding and quantifying the mechanical properties of clots is important to our ability to treat and prevent thromboembolic disease. However, assessing these properties from in vivo clots is experimentally challenging. Therefore, we and others have turned to studying in vitro clot mimics instead. Unfortunately, there are significant discrepancies in the reported properties of these clot mimics, which have been hypothesized to arise from differences in experimental techniques and blood sources. The goal of our current work is therefore to compare the mechanical behavior of clots made from the two most common sources, human and bovine blood, using the same experimental techniques. To this end, we tested clots under pure shear with and without initial cracks, under cyclic loading, and under stress relaxation. Based on these data, we computed and compared stiffness, strength, work-to-rupture, fracture toughness, relaxation time constants, and prestrain. While clots from both sources behaved qualitatively similarly, they differed quantitatively in almost every metric. We also correlated each mechanical metric to measures of blood composition. Thereby, we traced this inter-species variability in clot mechanics back to significant differences in hematocrit, but not platelet count. Thus, our work suggests that the results of past studies that have used bovine blood to make in vitro mimics - without adjusting blood composition - should be interpreted carefully. Future studies about the mechanical properties of blood clots should focus on human blood alone.

A Prospective, Single-Arm Study to Evaluate the Safety and Efficacy of an Autologous Blood Clot Product in the Treatment of Anal Fistula

BACKGROUND

Surgical treatment of complex perianal fistula is technically challenging, associated with risk of failure, and may require multiple procedures. In recent years, several biologic agents have been developed for permanently eradicating anal fistulous disease with variable success. In this study, the treatment is an autologous whole-blood product created from the patients' blood. It forms a provisional matrix that was found to be safe and effective in healing acute and chronic cutaneous wounds.

OBJECTIVE

The study aimed to assess the efficacy and safety of an autologous blood clot product as a treatment for transsphincteric perianal fistulas.

DESIGN

A prospective single-arm study.

SETTINGS

A single tertiary medical center.

PATIENTS

Patients with simple or complex transsphincteric fistulas confirmed by MRI were included in the study. Cause was either cryptoglandular or Crohn's disease related (in the absence of active luminal bowel disease).

INTERVENTION

The outpatient procedure was performed under general anesthesia and consisted of: 1) physical debridement and cleansing of the fistula tract; 2) suture closure of the internal opening; and 3) instillation of the autologous blood clot product into the entire tract.

MAIN OUTCOME MEASURES

Safety and efficacy at 6- and 12-months after surgery.

RESULTS

Fifty-three patients (77% men) with a median age of 42 (20-72) years were included in the study. Three patients withdrew consent, and 1 patient was lost to follow-up. At the time of this interim analysis, 49 and 33 patients completed the 6- and 12-month follow-up period. Thirty-four of the 49 patients achieved complete healing (69%) at 6 months, but 20 of the 33 patients (60%) achieved healing after 1 year. All patients who achieved healing at 6 months remained healed at the 1-year mark. In a subgroup analysis of patients with Crohn's disease, 7 of 9 patients completed 1-year follow-up, with 5 patients (71%) achieving clinical remission. No major side effects or postoperative complications were noted, but 2 adverse events occurred (admission for pain control and coronavirus 2019 infection).

LIMITATIONS

Noncomparative single-arm pilot study.

CONCLUSIONS

Treatment with an autologous blood clot product in perianal fistular disease was found to be feasible and safe, with an acceptable healing rate in both cryptoglandular and Crohn's disease fistula-in-ano. Further comparative assessment is required to determine its potential role in the treatment paradigm of fistula-in-ano. See Video Abstract .

BRAZO PARA EVALUAR LA SEGURIDAD Y EFICACIA DE RDVER, UN COGULO DE SANGRE AUTLOGO, EN EL TRATAMIENTO DE LA FSTULA ANAL

ANTECEDENTES:El tratamiento quirúrgico de la fístula perianal compleja es técnicamente desafiante, se asocia con riesgo de fracaso y puede requerir múltiples procedimientos. En los últimos años, se han desarrollado varios agentes biológicos con el fin de erradicar permanentemente la enfermedad fistulosa anal con éxito variable. El tratamiento RD2-Ver.02 es un producto de sangre total autólogo creado a partir de la sangre de los pacientes, que forma una matriz provisional que resultó segura y eficaz para curar heridas cutáneas agudas y crónicas.OBJETIVO:Evaluar la eficacia y seguridad de RD2-Ver.02 como tratamiento para las fístulas perianales transesfinterianas.DISEÑO:Un estudio prospectivo de un solo brazo.LUGARES:Un único centro médico terciario.PACIENTES:Se incluyeron en el estudio pacientes con fístulas transesfinterianas simples o complejas confirmadas mediante resonancia magnética. La etiología fue criptoglandular o relacionada con la enfermedad de Crohn (en ausencia de enfermedad intestinal luminal activa).INTERVENCIÓN:El procedimiento ambulatorio se realizó bajo anestesia general y consistió en: 1) desbridamiento físico y limpieza del trayecto fistuloso; 2) cierre con sutura de la abertura interna; y 3) instilación de RD2-Ver.02 en todo el tracto.PRINCIPALES MEDIDAS DE VALORACIÓN:Seguridad y eficacia a los 6 y 12 meses después de la cirugía.RESULTADOS:Se incluyeron en el estudio 53 pacientes (77% varones) con una mediana de edad de 42 (20-72) años. Tres pacientes retiraron su consentimiento y un paciente se perdió durante el seguimiento. En el momento de este análisis intermedio, 49 y 33 pacientes completaron el período de seguimiento de 6 y 12 meses, respectivamente. Treinta y cuatro (34) pacientes lograron una curación completa (69%) a los 6 meses, mientras que 20 de 33 pacientes (60%) lograron una curación después de un año. Todos los pacientes que lograron la curación a los 6 meses permanecieron curados al año. En un análisis de subgrupos de pacientes con enfermedad de Crohn, 7/9 pacientes completaron un seguimiento de un año y 5 pacientes (71%) alcanzaron la remisión clínica. No se observaron efectos secundarios importantes ni complicaciones postoperatorias, mientras que ocurrieron 2 eventos adversos (ingreso para control del dolor e infección por COVID-19).LIMITACIONES:Estudio piloto no comparativo de un solo brazo.CONCLUSIONES:Se encontró que el tratamiento con RD2-Ver.02 en la enfermedad fístula perianal es factible y seguro, con una tasa de curación aceptable tanto en la fístula criptoglandular como en la de Crohn en el ano. Se requiere una evaluación comparativa adicional para determinar su papel potencial en el paradigma de tratamiento de la fístula anal. (Pre-proofed version ).

Hydrogels and Wound Healing: Current and Future Prospects

The care and rehabilitation of acute and chronic wounds have a significant social and economic impact on patients and global health. This burden is primarily due to the adverse effects of infections, prolonged recovery, and the associated treatment costs. Chronic wounds can be treated with a variety of approaches, which include surgery, negative pressure wound therapy, wound dressings, and hyperbaric oxygen therapy. However, each of these strategies has an array of limitations. The existing dry wound dressings lack functionality in promoting wound healing and exacerbating pain by adhering to the wound. Hydrogels, which are commonly polymer-based and swell in water, have been proposed as potential remedies due to their ability to provide a moist environment that facilitates wound healing. Their unique composition enables them to absorb wound exudates, exhibit shape adaptability, and be modified to incorporate active compounds such as growth factors and antibacterial compounds. This review provides an updated discussion of the leading natural and synthetic hydrogels utilized in wound healing, details the latest advancements in hydrogel technology, and explores alternate approaches in this field. Search engines Scopus, PubMed, Science Direct, and Web of Science were utilized to review the advances in hydrogel applications over the last fifteen years.

Elasticity of whole blood clots measured via Volume Controlled Cavity Expansion

Measuring and understanding the mechanical properties of blood clots can provide insights into disease progression and the effectiveness of potential treatments. However, several limitations hinder the use of standard mechanical testing methods to measure the response of soft biological tissues, like blood clots. These tissues can be difficult to mount, and are inhomogeneous, irregular in shape, scarce, and valuable. To remedy this, we employ in this work Volume Controlled Cavity Expansion (VCCE), a technique that was recently developed, to measure local mechanical properties of soft materials in their natural environment. Through highly controlled volume expansion of a water bubble at the tip of an injection needle, paired with simultaneous measurement of the resisting pressure, we obtain a local signature of whole blood clot mechanical response. Comparing this data with predictive theoretical models, we find that a 1-term Ogden model is sufficient to capture the nonlinear elastic response observed in our experiments and produces shear modulus values that are comparable to values reported in the literature. Moreover, we find that bovine whole blood stored at 4 °C for greater than 2 days exhibits a statistically significant shift in the shear modulus from 2.53 ± 0.44 kPa on day 2 (N = 13) to 1.23 ± 0.18 kPa on day 3 (N = 14). In contrast to previously reported results, our samples did not exhibit viscoelastic rate sensitivity within strain rates ranging from 0.22 - 21.1 s-1. By surveying existing data on whole blood clots for comparison, we show that this technique provides highly repeatable and reliable results, hence we propose the more widespread adoption of VCCE as a path forward to building a better understanding of the mechanics of soft biological materials.

A Brief Review on Cerium Oxide (CeO2NPs)-Based Scaffolds: Recent Advances in Wound Healing Applications

The process of wound healing is complex and involves the interaction of multiple cells, each with a distinct role in the inflammatory, proliferative, and remodeling phases. Chronic, nonhealing wounds may result from reduced fibroblast proliferation, angiogenesis, and cellular immunity, often associated with diabetes, hypertension, vascular deficits, immunological inadequacies, and chronic renal disease. Various strategies and methodologies have been explored to develop nanomaterials for wound-healing treatment. Several nanoparticles such as gold, silver, cerium oxide and zinc possess antibacterial properties, stability, and a high surface area that promotes efficient wound healing. In this review article, we investigate the effectiveness of cerium oxide nanoparticles (CeO₂NPs) in wound healing-particularly the effects of reducing inflammation, enhancing hemostasis and proliferation, and scavenging reactive oxygen species. The mechanism enables CeO₂NPs to reduce inflammation, modulate the immunological system, and promote angiogenesis and tissue regeneration. In addition, we investigate the efficacy of cerium oxide-based scaffolds in various wound-healing applications for creating a favorable wound-healing environment. Cerium oxide nanoparticles (CeO₂NPs) exhibit antioxidant, anti-inflammatory, and regenerative characteristics, enabling them to be ideal wound healing material. Investigations have shown that CeO₂NPs can stimulate wound closure, tissue regeneration, and scar reduction. CeO₂NPs may also reduce bacterial infections and boost wound-site immunity. However, additional study is needed to determine the safety and efficacy of CeO₂NPs in wound healing and their long-term impacts on human health and the environment. The review reveals that CeO₂NPs have promising wound-healing properties, but further study is needed to understand their mechanisms of action and ensure their safety and efficacy.

Surface-Modified Melt Coextruded Nanofibers Enhance Blood Clotting In Vitro

Blood loss causes an estimated 1.9 million deaths per year globally, making new methods to stop bleeding and promote clot formation immediately following injury paramount. The fabrication of functional hemostatic materials has the potential to save countless lives by limiting bleeding and promoting clot formation following an injury. This work describes the melt manufacturing of poly(ε-caprolactone) nanofibers and their chemical functionalization to produce highly scalable materials with enhanced blood clotting properties. The nanofibers are manufactured using a high throughput melt coextrusion method. Once isolated, the nanofibers are functionalized with polymers that promote blood clotting through surface-initiated atom transfer radical polymerization. The functional nanofibers described herein speed up the coagulation cascade and produce more robust blood clots, allowing for the potential use of these functional nonwoven mats as advanced bandages.

Structural control of fibrin bioactivity by mechanical deformation

SignificanceFibrin plays a vital role in biology as the fibrous network that stabilizes blood clots and also through interaction with numerous blood components. While much is known about fibrin mechanics, comparatively little is known about how fibrin's mechanics influence its biochemistry. We show that structural changes in fibrin under mechanical tension reduces binding of tissue plasminogen activator, an enzyme that initiates lysis. Furthermore, these structural transitions also led to decreased platelet activation through suppressed binding between platelet integrins and fibrin. Our work shows that fibrin possesses an intrinsic mechano-chemical feedback loop that regulates its bioactivity via molecular structural rearrangements.