Liquid-embedded (bio)printing of alginate-free, standalone, ultrafine, and ultrathin-walled cannular structures.

While there has been considerable success in the three-dimensional bioprinting of relatively large standalone filamentous tissues, the fabrication of solid fibers with ultrafine diameters or those cannular featuring ultrathin walls remains a particular challenge. Here, an enabling strategy for (bio)printing of solid and hollow fibers whose size ranges could be facilely adjusted across a broad spectrum, is reported, using an aqueous two-phase embedded (bio)printing approach combined with specially designed cross-linking and extrusion methods. The generation of standalone, alginate-free aqueous architectures using this aqueous two-phase strategy allowed freeform patterning of aqueous bioinks, such as those composed of gelatin methacryloyl, within the immiscible aqueous support bath of poly(ethylene oxide). Our (bio)printing strategy revealed the fabrication of standalone solid or cannular structures with diameters as small as approximately 3 or 40 µm, respectively, and wall thicknesses of hollow conduits down to as thin as <5 µm. With cellular functions also demonstrated, we anticipate the methodology to serve as a platform that may satisfy the needs for the different types of potential biomedical and other applications in the future, especially those pertaining to cannular tissues of ultrasmall diameters and ultrathin walls used toward regenerative medicine and tissue model engineering.

Targeting oncogenic KRAS with molecular brush-conjugated antisense oligonucleotides.

The mutant form of the guanosine triphosphatase (GTPase) KRAS is a key driver in human tumors but remains a challenging therapeutic target, making KRASMUT cancers a highly unmet clinical need. Here, we report a class of bottlebrush polyethylene glycol (PEG)-conjugated antisense oligonucleotides (ASOs) for potent in vivo KRAS depletion. Owing to their highly branched architecture, these molecular nanoconstructs suppress nearly all side effects associated with DNA-protein interactions and substantially enhance the pharmacological properties of the ASO, such as plasma pharmacokinetics and tumor uptake. Systemic delivery to mice bearing human non-small-cell lung carcinoma xenografts results in a significant reduction in both KRAS levels and tumor growth, and the antitumor performance well exceeds that of current popular ASO paradigms, such as chemically modified oligonucleotides and PEGylation using linear or slightly branched PEG. Importantly, these conjugates relax the requirement on the ASO chemistry, allowing unmodified, natural phosphodiester ASOs to achieve efficacy comparable to that of chemically modified ones. Both the bottlebrush polymer and its ASO conjugates appear to be safe and well tolerated in mice. Together, these data indicate that the molecular brush-ASO conjugate is a promising therapeutic platform for the treatment of KRAS-driven human cancers and warrant further preclinical and clinical development.

Microgels for Cell Delivery in Tissue Engineering and Regenerative Medicine.

Microgels prepared from natural or synthetic hydrogel materials have aroused extensive attention as multifunctional cells or drug carriers, that are promising for tissue engineering and regenerative medicine. Microgels can also be aggregated into microporous scaffolds, promoting cell infiltration and proliferation for tissue repair. This review gives an overview of recent developments in the fabrication techniques and applications of microgels. A series of conventional and novel strategies including emulsification, microfluidic, lithography, electrospray, centrifugation, gas-shearing, three-dimensional bioprinting, etc. are discussed in depth. The characteristics and applications of microgels and microgel-based scaffolds for cell culture and delivery are elaborated with an emphasis on the advantages of these carriers in cell therapy. Additionally, we expound on the ongoing and foreseeable applications and current limitations of microgels and their aggregate in the field of biomedical engineering. Through stimulating innovative ideas, the present review paves new avenues for expanding the application of microgels in cell delivery techniques.

Rapid Volumetric Bioprinting of Decellularized Extracellular Matrix Bioinks.

Decellularized extracellular matrix (dECM)-based hydrogels are widely applied to additive biomanufacturing strategies for relevant applications. The extracellular matrix components and growth factors of dECM play crucial roles in cell adhesion, growth, and differentiation. However, the generally poor mechanical properties and printability have remained as major limitations for dECM-based materials. In this study, heart-derived dECM (h-dECM) and meniscus-derived dECM (Ms-dECM) bioinks in their pristine, unmodified state supplemented with the photoinitiator system of tris(2,2-bipyridyl) dichlororuthenium(II) hexahydrate and sodium persulfate, demonstrate cytocompatibility with volumetric bioprinting processes. This recently developed bioprinting modality illuminates a dynamically evolving light pattern into a rotating volume of the bioink, and thus decouples the requirement of mechanical strengths of bioprinted hydrogel constructs with printability, allowing for the fabrication of sophisticated shapes and architectures with low-concentration dECM materials that set within tens of seconds. As exemplary applications, cardiac tissues are volumetrically bioprinted using the cardiomyocyte-laden h-dECM bioink showing favorable cell proliferation, expansion, spreading, biomarker expressions, and synchronized contractions; whereas the volumetrically bioprinted Ms-dECM meniscus structures embedded with human mesenchymal stem cells present appropriate chondrogenic differentiation outcomes. This study supplies expanded bioink libraries for volumetric bioprinting and broadens utilities of dECM toward tissue engineering and regenerative medicine.

Thiamine-deficient optic neuropathy associated with Wernicke's encephalopathy in patients with chronic diarrhea.

The deficiency of thiamine manifesting as Wernicke's encephalopathy (WE) and concurrent optic neuropathy is rare. Herein, we report the case of a 29-year-old patient who suffered from bilateral sudden blindness and a disturbance of consciousness after 2 months of chronic diarrhea and minimal food intake. In addition, bilateral abducens nerve palsy with multidirectional nystagmus and no light perception in both eyes were noted. An ophthalmoscopic examination revealed bilateral disc edema with peripapillary flame-shaped hemorrhages. Although the results of analyzing the composition of cerebrospinal fluid showed that they are within normal limits, magnetic resonance imaging (MRI) revealed bilateral hyperintensity over the mammillary body, dorsal medial thalamus, and periaqueductal gray matter. As we suspected thiamine deficiency-induced WE, a high dose of intravenous thiamine was prescribed. After the administration of thiamine, both visual acuity and visual field rapidly improved with the simultaneous recovery of consciousness. This case indicates that, although rare, thiamine deficiency with WE may still occur in patients with chronic diarrhea in Taiwan. Thiamine deficiency should be considered in the differential diagnosis for patients who encounter sudden visual loss after prolonged periods of poor food intake and poor vitamin supplementation.

A 3D Bioprinted Gut Anaerobic Model for Studying Bacteria-Host Interactions.

The role of the human intestinal tract in host-microbe interactions has been highlighted in recent years. Several 3-dimensional (3D) models have been developed to reproduce the physiological characteristics of the human gut and to investigate the function of the gut microbiota. One challenge for 3D models is to recapitulate the low oxygen concentrations in the intestinal lumen. Moreover, most earlier 3D culture systems used a membrane to physically separate bacteria from the intestinal epithelium, which has sometimes made the studies of bacteria adhering to or invading cells less feasible. We report the establishment of a 3D gut epithelium model and cultured it at high cell viability under an anaerobic condition. We further cocultured intestinal bacteria including both commensal and pathogen directly with epithelial cells in the established 3D model under the anaerobic condition. We subsequently compared the gene expression differences of aerobic and anaerobic conditions for cell and bacterial growth via dual RNA sequencing. Our study provides a physiologically relevant 3D gut epithelium model that mimics the anaerobic condition in the intestinal lumen and supplies a powerful system for future in-depth gut-microbe interactional investigations.

Advances in volumetric bioprinting.

The three-dimensional (3D) bioprinting technologies are suitable for biomedical applications owing to their ability to manufacture complex and high-precision tissue constructs. However, the slow printing speed of current layer-by-layer (bio)printing modality is the major limitation in biofabrication field. To overcome this issue, volumetric bioprinting (VBP) is developed. VBP changes the layer-wise operation of conventional devices, permitting the creation of geometrically complex, centimeter-scale constructs in tens of seconds. VBP is the next step onward from sequential biofabrication methods, opening new avenues for fast additive manufacturing in the fields of tissue engineering, regenerative medicine, personalized drug testing, and soft robotics, etc. Therefore, this review introduces the printing principles and hardware designs of VBP-based techniques; then focuses on the recent advances in VBP-based (bio)inks and their biomedical applications. Lastly, the current limitations of VBP are discussed together with future direction of research.

Volumetric additive manufacturing of pristine silk-based (bio)inks.

Volumetric additive manufacturing (VAM) enables fast photopolymerization of three-dimensional constructs by illuminating dynamically evolving light patterns in the entire build volume. However, the lack of bioinks suitable for VAM is a critical limitation. This study reports rapid volumetric (bio)printing of pristine, unmodified silk-based (silk sericin (SS) and silk fibroin (SF)) (bio)inks to form sophisticated shapes and architectures. Of interest, combined with post-fabrication processing, the (bio)printed SS constructs reveal properties including reversible as well as repeated shrinkage and expansion, or shape-memory; whereas the (bio)printed SF constructs exhibit tunable mechanical performances ranging from a few hundred Pa to hundreds of MPa. Both types of silk-based (bio)inks are cytocompatible. This work supplies expanded bioink libraries for VAM and provides a path forward for rapid volumetric manufacturing of silk constructs, towards broadened biomedical applications.

High-throughput screens identify a lipid nanoparticle that preferentially delivers mRNA to human tumors in vivo.

Lipid nanoparticles (LNPs) are a clinically relevant way to deliver therapeutic mRNA to hepatocytes in patients. However, LNP-mRNA delivery to end-stage solid tumors such as head and neck squamous cell carcinoma (HNSCC) remains more challenging. While scientists have used in vitro assays to evaluate potential nanoparticles for HNSCC delivery, high-throughput delivery assays performed directly in vivo have not been reported. Here we use a high-throughput LNP assay to evaluate how 94 chemically distinct nanoparticles delivered nucleic acids to HNSCC solid tumors in vivo. DNA barcodes were used to identify LNPHNSCC, a novel LNP for systemic delivery to HNSCC solid tumors. Importantly, LNPHNSCC retains tropism to HNSCC solid tumors while minimizing off-target delivery to the liver.

A multifunctional micropore-forming bioink with enhanced anti-bacterial and anti-inflammatory properties.

Three-dimensional (3D) bioprinting has emerged as an enabling tool for various biomedical applications, such as tissue regeneration and tissue model engineering. To this end, the development of bioinks with multiple functions plays a crucial role in the applications of 3D bioprinting technologies. In this study, we propose a new bioink based on two immiscible aqueous phases of gelatin methacryloyl (GelMA) and dextran, further endowed with anti-bacterial and anti-inflammatory properties. This micropore-forming GelMA-dextran (PGelDex) bioink exhibited excellent printability with vat-polymerization, extrusion, and handheld bioprinting methods. The porous structure was confirmed after bioprinting, which promoted the spreading of the encapsulated cells, exhibiting the exceptional cytocompatibility of this bioink formulation. To extend the applications of such a micropore-forming bioink, interleukin-4 (IL-4)-loaded silver-coated gold nanorods (AgGNRs) and human mesenchymal stem cells (MSCs) were simultaneously incorporated, to display synergistic anti-infection behavior and immunomodulatory function. The results revealed the anti-bacterial properties of the AgGNR-loaded PGelDex bioink for both Gram-negative and Gram-positive bacteria. The data also indicated that the presence of IL-4 and MSCs facilitated macrophage M2-phenotype differentiation, suggesting the potential anti-inflammatory feature of the bioink. Overall, this unique anti-bacterial and immunomodulatory micropore-forming bioink offers an effective strategy for the inhibition of bacterial-induced infections as well as the ability of immune-regulation, which is a promising candidate for broadened tissue bioprinting applications.

Uniaxial and Coaxial Vertical Embedded Extrusion Bioprinting.

The 3D bioprinting technologies have attracted increasing attention due to their flexibility in producing architecturally relevant tissue constructs. Here, a vertical embedded extrusion bioprinting strategy using uniaxial or coaxial nozzles is presented, which allows formation of vertical structures of homogeneous or heterogeneous properties. By adjusting the bioprinting parameters, the characteristics of the bioprinted vertical patterns can be precisely controlled. Using this strategy, two proof-of-concept applications in tissue biofabrication are demonstrated. Specifically, intestinal villi and hair follicles, two liner-shaped tissues in the human body, are successfully generated with the vertical embedded bioprinting method, reconstructing some of their key structures as well as restoring partial functions in vitro. Caco-2 cells in the bioprinted intestinal villus constructs proliferated and aggregated properly, also showing functional biomarker expressions such as ZO-1 and villin. Moreover, preliminary hair follicle structures featuring keratinized human keratinocytes and spheroid-shaped human dermal papilla cells are formed after vertical bioprinting and culturing. In summary, this vertical embedded extrusion bioprinting technique harnessing a uniaxial or coaxial format will likely bring further improvements in the reconstruction of certain human tissues and organs, especially those with a linear structure, potentially leading to wide utilities in tissue engineering, tissue model engineering, and drug discovery.

Vertical Extrusion Cryo(bio)printing for Anisotropic Tissue Manufacturing.

Due to the poor mechanical properties of many hydrogel bioinks, conventional 3D extrusion bioprinting is usually conducted based on the X-Y plane, where the deposited layers are stacked in the Z-direction with or without the support of prior layers. Herein, a technique is reported, taking advantage of a cryoprotective bioink to enable direct extrusion bioprinting in the vertical direction in the presence of cells, using a freezing plate with precise temperature control. Of interest, vertical 3D cryo-bioprinting concurrently allows the user to create freestanding filamentous constructs containing interconnected, anisotropic microchannels featuring gradient sizes aligned in the vertical direction, also associated with enhanced mechanical performances. Skeletal myoblasts within the 3D-cryo-bioprinted hydrogel constructs show enhanced cell viability, spreading, and alignment, compared to the same cells in the standard hydrogel constructs. This method is further extended to a multimaterial format, finding potential applications in interface tissue engineering, such as creation of the muscle-tendon unit and the muscle-microvascular unit. The unique vertical 3D cryo-bioprinting technique presented here suggests improvements in robustness and versatility to engineer certain tissue types especially those anisotropic in nature, and may extend broad utilities in tissue engineering, regenerative medicine, drug discovery, and personalized therapeutics.

Microfluidic bioprinting of tough hydrogel-based vascular conduits for functional blood vessels.

Three-dimensional (3D) bioprinting of vascular tissues that are mechanically and functionally comparable to their native counterparts is an unmet challenge. Here, we developed a tough double-network hydrogel (bio)ink for microfluidic (bio)printing of mono- and dual-layered hollow conduits to recreate vein- and artery-like tissues, respectively. The tough hydrogel consisted of energy-dissipative ionically cross-linked alginate and elastic enzyme-cross-linked gelatin. The 3D bioprinted venous and arterial conduits exhibited key functionalities of respective vessels including relevant mechanical properties, perfusability, barrier performance, expressions of specific markers, and susceptibility to severe acute respiratory syndrome coronavirus 2 pseudo-viral infection. Notably, the arterial conduits revealed physiological vasoconstriction and vasodilatation responses. We further explored the feasibility of these conduits for vascular anastomosis. Together, our study presents biofabrication of mechanically and functionally relevant vascular conduits, showcasing their potentials as vascular models for disease studies in vitro and as grafts for vascular surgeries in vivo, possibly serving broad biomedical applications in the future.

[Progress of research in the improvement of the antithrombogenic property of biomedical polyurethane].

The progress of research of the physical and chemical modification methods to improve the antithrombogenic property of biomedical polyurethane (PU) in the past five years is reviewed in this paper. The physical modification method includes physical blending, physical vapor deposition (PVD) and replication molding technique. Meanwhile, chemical modification method is focused on the covalent bonding to immobilized special molecular. Moreover, the covalent bonding method covered functionalizing the PU surface with tailor-made groups in the bulk and the activation of the surface to form unstable active sites for further reactions.

Hypocalcemic seizure mistaken for idiopathic epilepsy in two cases of DiGeorge syndrome (chromosome 22q11 deletion syndrome).

The chromosome 22q11 deletion syndrome, which is synonymous with DiGeorge syndrome, is a congenital anomaly characterized by abnormal facies, congenital heart defects, hypoparathyroidism with hypocalcemia, and immunodeficiency. Neurological manifestations of the chromosome 22q11 deletion syndrome are variable, and include mental deficiency, speech disturbances, learning difficulties, attention deficit hyperactivity disorder, and epilepsy. Hypoparathyroidism and hypocalcemia cause recurrent seizures if patients are not properly treated. We present two patients with poorly controlled epileptic seizures that turned out to be caused by DiGeorge syndrome with hypocalcemia. For such patients, the definitive treatment of seizures depends on recognition of this syndrome and correction of the hypocalcemic state, rather than the use of anticonvulsants.