Multifunctional self-healing hydrogels via nanoengineering of colloidal and polymeric cellulose

The unique features of self-healing hydrogels hold great potential for biomedical applications including injectable hydrogels for cancer treatment, procedures for tumor removal or resection. However, the fabrication of durable and multifunctional self-healing hydrogels composed of biocompatible, green building blocks via versatile synthetic methodology continues to pose a significant challenge. Here, we engineered dialdehyde cellulose (DAC, as a macromolecular bio-crosslinker), and electrosterically stabilized nanocrystalline cellulose (ENCC, as a ligand-targeted drug carrier) to facilitate a strategy for the construction of self-healing hydrogels. Benefiting from its high carboxyl group density, ENCC was functionalized with folic acid (FA) using a non-toxic DMTMM coupling agent and loaded with doxorubicin (DOX, a model drug) through electrostatic interactions. A natural self-healing hydrogel was prepared from carboxymethyl chitosan (CCTS) and DAC mixed with DOX-loaded FA-ENCC using dynamic Schiff-base and hydrogen linkages. A combination of active supramolecular and vital covalent junctions led to a soft (storage modulus ∼500 Pa) and durable material, with rapid (< 5 min) reconstruction of molecular structure from fractured and injected to intact forms. The DAC-CCTS hydrogel showed an appreciable loading capacity of ∼5 mg g-1. Biocompatibility of the hydrogels was evaluated using cell viability and metabolic activity assays, showing lower metabolic activity due to sustained release of its cargo. These materials offer a versatile, sustainable, and green platform for the efficient construction of hydrogels, based on macro- and nano-engineered cellulose, the most abundant and easily accessible biopolymer.

Accelerating Patterned Vascularization Using Granular Hydrogel Scaffolds and Surgical Micropuncture

Bulk hydrogel scaffolds are common in reconstructive surgery. They allow for the staged repair of soft tissue loss by providing a base for revascularization. Unfortunately, they are limited by both slow and random vascularization, which may manifest as treatment failure or suboptimal repair. Rapidly inducing patterned vascularization within biomaterials has profound translational implications for current clinical treatment paradigms and the scaleup of regenerative engineering platforms. To address this long-standing challenge, a novel microsurgical approach and granular hydrogel scaffold (GHS) technology are co-developed to hasten and pattern microvascular network formation. In surgical micropuncture (MP), targeted recipient blood vessels are perforated using a microneedle to accelerate cell extravasation and angiogenic outgrowth. By combining MP with an adjacent GHS with precisely tailored void space architecture, microvascular pattern formation as assessed by density, diameter, length, and intercapillary distance is rapidly guided. This work opens new translational opportunities for microvascular engineering, advancing reconstructive surgery, and regenerative medicine.

Iron inhibits glioblastoma cell migration and polarization

Glioblastoma is one of the deadliest malignancies facing modern oncology today. The ability of glioblastoma cells to diffusely spread into neighboring healthy brain makes complete surgical resection nearly impossible and contributes to the recurrent disease faced by most patients. Although research into the impact of iron on glioblastoma has addressed proliferation, there has been little investigation into how cellular iron impacts the ability of glioblastoma cells to migrate-a key question, especially in the context of the diffuse spread observed in these tumors. Herein, we show that increasing cellular iron content results in decreased migratory capacity of human glioblastoma cells. The decrease in migratory capacity was accompanied by a decrease in cellular polarization in the direction of movement. Expression of CDC42, a Rho GTPase that is essential for both cellular migration and establishment of polarity in the direction of cell movement, was reduced upon iron treatment. We then analyzed a single-cell RNA-seq dataset of human glioblastoma samples and found that cells at the tumor periphery had a gene signature that is consistent with having lower levels of cellular iron. Altogether, our results suggest that cellular iron content is impacting glioblastoma cell migratory capacity and that cells with higher iron levels exhibit reduced motility.

Dynein-Powered Cell Locomotion Guides Metastasis of Breast Cancer

The principal cause of death in cancer patients is metastasis, which remains an unresolved problem. Conventionally, metastatic dissemination is linked to actomyosin-driven cell locomotion. However, the locomotion of cancer cells often does not strictly line up with the measured actomyosin forces. Here, a complementary mechanism of metastatic locomotion powered by dynein-generated forces is identified. These forces arise within a non-stretchable microtubule network and drive persistent contact guidance of migrating cancer cells along the biomimetic collagen fibers. It is also shown that the dynein-powered locomotion becomes indispensable during invasive 3D migration within a tissue-like luminal network formed by spatially confining granular hydrogel scaffolds (GHS) made up of microscale hydrogel particles (microgels). These results indicate that the complementary motricity mediated by dynein is always necessary and, in certain instances, sufficient for disseminating metastatic breast cancer cells. These findings advance the fundamental understanding of cell locomotion mechanisms and expand the spectrum of clinical targets against metastasis.

Dynein-Powered Cell Locomotion Guides Metastasis of Breast Cancer

Metastasis is a principal cause of death in cancer patients, which remains an unresolved fundamental and clinical problem. Conventionally, metastatic dissemination is linked to the actomyosin-driven cell locomotion. However, locomotion of cancer cells often does not strictly line up with the measured actomyosin forces. Here, we identify a complementary mechanism of metastatic locomotion powered by the dynein-generated forces. These forces that arise within a non-stretchable microtubule network drive persistent contact guidance of migrating cancer cells along the biomimetic collagen fibers. We also show that dynein-powered locomotion becomes indispensable during invasive 3D migration within a tissue-like luminal network between spatially confining hydrogel microspheres. Our results indicate that the complementary contractile system of dynein motors and microtubules is always necessary and in certain instances completely sufficient for dissemination of metastatic breast cancer cells. These findings advance fundamental understanding of cell locomotion mechanisms and expand the spectrum of clinical targets against metastasis.

Gelatin Methacryloyl Granular Hydrogel Scaffolds: High-throughput Microgel Fabrication, Lyophilization, Chemical Assembly, and 3D Bioprinting

The emergence of granular hydrogel scaffolds (GHS), fabricated via assembling hydrogel microparticles (HMPs), has enabled microporous scaffold formation in situ. Unlike conventional bulk hydrogels, interconnected microscale pores in GHS facilitate degradation-independent cell infiltration as well as oxygen, nutrient, and cellular byproduct transfer. Methacryloyl-modified gelatin (GelMA), a (photo)chemically crosslinkable, protein-based biopolymer containing cell adhesive and biodegradable moieties, has widely been used as a cell-responsive/instructive biomaterial. Converting bulk GelMA to GHS may open a plethora of opportunities for tissue engineering and regeneration. In this article, we demonstrate the procedures of high-throughput GelMA microgel fabrication, conversion to resuspendable dry microgels (micro-aerogels), GHS formation via the chemical assembly of microgels, and granular bioink fabrication for extrusion bioprinting. We show how a sequential physicochemical treatment via cooling and photocrosslinking enables the formation of mechanically robust GHS. When light is inaccessible (e.g., during deep tissue injection), individually crosslinked GelMA HMPs may be bioorthogonally assembled via enzymatic crosslinking using transglutaminases. Finally, three-dimensional (3D) bioprinting of microporous GHS at low HMP packing density is demonstrated via the interfacial self-assembly of heterogeneously charged nanoparticles.

Nanoengineered Granular Hydrogel Bioinks with Preserved Interconnected Microporosity for Extrusion Bioprinting

3D bioprinting of granular hydrogels comprising discrete hydrogel microparticles (microgels) may overcome the intrinsic structural limitations of bulk (nanoporous) hydrogel bioinks, enabling the fabrication of modular thick tissue constructs. The additive manufacturing of granular scaffolds has predominantly relied on highly jammed microgels to render the particulate suspensions shear yielding and extrudable. This inevitably compromises void spaces between microgels (microporosity), defeating rapid cell penetration, facile metabolite and oxygen transfer, and cell viability. Here, this persistent bottleneck is overcome by programming microgels with reversible interfacial nanoparticle self-assembly, enabling the fabrication of nanoengineered granular bioinks (NGB) with well-preserved microporosity, enhanced printability, and shape fidelity. The microporous architecture of bioprinted NGB constructs permits immediate post-printing 3D cell seeding, which may expand the library of bioinks via circumventing the necessity of bioorthogonality for cell-laden scaffold formation. This work opens new opportunities for the 3D bioprinting of tissue engineering microporous scaffolds beyond the traditional biofabrication window.

3D bioprinting for reconstituting the cancer microenvironment

The cancer microenvironment is known for its complexity, both in its content as well as its dynamic nature, which is difficult to study using two-dimensional (2D) cell culture models. Several advances in tissue engineering have allowed more physiologically relevant three-dimensional (3D) in vitro cancer models, such as spheroid cultures, biopolymer scaffolds, and cancer-on-a-chip devices. Although these models serve as powerful tools for dissecting the roles of various biochemical and biophysical cues in carcinoma initiation and progression, they lack the ability to control the organization of multiple cell types in a complex dynamic 3D architecture. By virtue of its ability to precisely define perfusable networks and position of various cell types in a high-throughput manner, 3D bioprinting has the potential to more closely recapitulate the cancer microenvironment, relative to current methods. In this review, we discuss the applications of 3D bioprinting in mimicking cancer microenvironment, their use in immunotherapy as prescreening tools, and overview of current bioprinted cancer models.

Does ghrelin level change after epileptic seizure in rats?

AIM

Epilepsy is one of the most common neurologic problems worldwide. A relationship between epilepsy and hormones has been demonstrated. This study was designed to investigate the effect of seizure on blood ghrelin level.

METHODS

Twenty male Wistar rats were divided into two groups. The control group received saline and the pentylenetetrazole (PTZ) group received a single convulsive dose (50mg/kg) of PTZ. Thirty minutes later blood samples were collected and acylated and unacylated ghrelin levels in the plasma were assayed.

RESULTS

Acylated or active form of ghrelin decreased significantly (p<0.05) after a PTZ-induced seizure, but the reduction of unacylated and total blood ghrelin levels failed to reach statistical significance.

CONCLUSION

These findings may reflect that PTZ-induced epilepsy decreases AG of plasma.