Novel microgel-based scaffolds to study the effect of degradability on human dermal fibroblasts

Advancements in Three Dimensional In-Vitro Cell Culture Models

The scientific field is observing a gradual shift from monolayer cultures to three-dimensional (3D) models, as they give a more relevant data in pre-clinical stages. This review summarizes the major techniques and materials used to develop 3D platforms, especially for cancer. It also discusses the challenges and some unresolved issues of the field and highlights some techniques that have made it to the market.

Non-destructive mechanical assessment for optimization of 3D bioprinted soft tissue scaffolds

Characterizing the mechanical properties of engineered tissue constructs provides powerful insight into the function of engineered tissues for their desired application. Current methods of mechanical characterization of soft hydrogels used in tissue engineering are often destructive and ignore the effect of 3D bioprinting on the overall mechanical properties of a whole tissue construct. This work reports on using a non-destructive method of viscoelastic analysis to demonstrate the influence of bioprinting strategy on mechanical properties of hydrogel tissue scaffolds. Structure-function relationships are developed for common 3D bioprinting parameters such as printed fiber size, printed scaffold pattern, and bioink formulation. Further studies include mechanical properties analysis during degradation, real-time monitoring of crosslinking, mechanical characterization of multi-material scaffolds, and monitoring the effect of encapsulated cell growth on the mechanical strength of 3D bioprinted scaffolds. We envision this method of characterization opening a new wave of understanding and strategy in tissue engineering.

Development of novel microenvironments for promoting enhanced wound healing

PURPOSE OF REVIEW

Nonhealing wounds are a significant issue facing the healthcare industry. Materials that modulate the wound microenvironment have the potential to improve healing outcomes.

RECENT FINDINGS

A variety of acellular and cellular scaffolds have been developed for regulating the wound microenvironment, including materials for controlled release of antimicrobials and growth factors, materials with inherent immunomodulative properties, and novel colloidal-based scaffolds. Scaffold construction methods include electrospinning, 3D printing, decellularization of extracellular matrix, or a combination of techniques. Material application methods include layering or injecting at the wound site.

SUMMARY

Though these techniques show promise for repairing wounds, all material strategies thus far struggle to induce regeneration of features such as sweat glands and hair follicles. Nonetheless, innovative technologies currently in the research phase may facilitate future attainment of these features. Novel methods and materials are constantly arising for the development of microenvironments for enhanced wound healing.

Manufacturing and physical characterization of absorbable oxidized regenerated cellulose braided surgical sutures

Suture is an important part of surgical operation, and closure of the wound associated with this procedure continuous to be a challenge in postoperative care. Currently, oxidized regenerated cellulose (ORC) is widely used in the absorption of hemostatic materials. However, there is no ORC medical suture product in the market. The objective of this article was to prepare novel braided sutures by TEMPO-mediated oxidation regenerated cellulose (TORC) to achieve a suturable material with biodegradability and ideal mechanical properties. Regenerated cellulose (RC) strands were made into sutures on a circular braiding machine, and TEMPO-mediated oxidation treatment was introduced alternatively after braiding. The RC sutures under different oxidation time were characterized by ATR-FTIR, electrical conductivity, XRD analysis, physical properties and in vitro degradation property. We further demonstrate that the RC sutures were oxidized and formed the carboxylic (-COOH) functional group. With the extension of oxidation duration, the carboxyl content in TORC sutures increased gradually from 5.1 to 10.4% and the strength, weight, and diameter of TORC sutures decreased gradually. Moreover, we proved that the knot-pull strength of TORC-45 declined by 77.8% after 28 days, thus this sutures fulfilled U.S. Pharmacopeia requirement of knot-pull strength. We have shown that TEMPO oxidation reaction significantly promoted the degradation of TORC sutures. Overall, TORC sutures were successfully produced with favorable biodegradability, revealing potential prospects of clinical applications.

Injectable Macroporous Hydrogel Formed by Enzymatic Cross-Linking of Gelatin Microgels

Injectable hydrogels can be useful tools for facilitating wound healing since they conform to the irregular shapes of wounds, serving as a temporary matrix during the healing process. However, the lack of inherent pore structures of most injectable hydrogels prohibits desired interactions with the cells of the surrounding tissues limiting their clinical efficacy. Here, we introduce a simple, cost-effective and highly biofunctional injectable macroporous hydrogel made of gelatin microgels crosslinked by microbial transglutaminase (mTG). Pores are created by the interstitial space among the microgels. A water-in-oil emulsion technique was used to create gelatin microgels of an average size of 250μm in diameter. When crosslinked with mTG, the microgels adhered to each other to form a bulk hydrogel with inherent pores large enough for cell migration. The viscoelastic properties of the porous hydrogel were similar to those of nonporous gelatin hydrogel made by adding mTG to a homogeneous gelatin solution. The porous hydrogel supported higher cellular proliferation of human dermal fibroblasts (hDFs) than the nonporous hydrogel over two weeks, and allowed the migration of hDFs into the pores. Conversely, the hDFs were unable to permeate the surface of the nonporous hydrogel. To demonstrate its potential use in wound healing, the gelatin microgels were injected with mTG into a cut out section of an excised porcine cornea. Due to the action of mTG, the porous hydrogel stably adhered to the cornea tissue for two weeks. Confocal images showed that a large number of cells from the cornea tissue migrated into the interstitial space of the porous hydrogel. The porous hydrogel was also used for the controlled release of platelet-derived growth factor (PDGF), increasing the proliferation of hDFs compared to the nonporous hydrogel. This gelatin microgel-based porous hydrogel will be a useful tool for wound healing and tissue engineering.