Self-enhancing sono-inks enable deep-penetration acoustic volumetric printing

Hydrogel-based 3D printing technology: From interfacial engineering to precision medicine

Advances in 3D printing technology and the development of hydrogel-based inks have significantly enhanced the potential of precision medicine, promoting progress in medical diagnosis and treatment. The development of 3D printing enables the fabrication of complex gradient structures that emulate natural tissue environments, while advancements in interface engineering facilitate the precise control of interface properties, thereby enhancing the performance of hydrogels in biomedical applications. This review focuses on the latest advancements in three critical 3D printing application areas: efficient real-time detection, drug delivery systems, and regenerative medicine. The application of 3D printing technology enhances nucleic acid-based molecular diagnostic platforms and wearable biosensors for real-time monitoring of physiological parameters, thereby providing robust support for early disease diagnosis. Additionally, it facilitates the development of targeted and controlled drug delivery systems, which offer promising methods for efficient drug utilization, and enables the construction of complex tissue and organ structures with bioactivity and functionality, providing new solutions for regenerative medicine. Collectively, these advancements propel the ongoing progress and development of precision medicine. Furthermore, the challenges associated with 3D printing technology in these three major applications are discussed along with an outlook on prospects.

Dynamic hierarchical ligand anisotropy for competing macrophage regulation in vivo

Diverse connective tissues exhibit hierarchical anisotropic structures that intricately regulate homeostasis and tissue functions for dynamic immune response modulation. In this study, remotely manipulable hierarchical nanostructures are tailored to exhibit multi-scale ligand anisotropy. Hierarchical nanostructure construction involves coupling liganded nanoscale isotropic/anisotropic Au (comparable to few integrin molecules-scale) to the surface of microscale isotropic/anisotropic magnetic Fe3O4 (comparable to integrin cluster-scale) and then elastically tethering them to a substrate. Systematic independent tailoring of nanoscale or microscale ligand isotropy versus anisotropy in four different hierarchical nanostructures with constant liganded surface area demonstrates similar levels of integrin molecule bridging and macrophage adhesion on the nanoscale ligand isotropy versus anisotropy. Conversely, the levels of integrin cluster bridging across hierarchical nanostructures and macrophage adhesion are significantly promoted by microscale ligand anisotropy compared with microscale ligand isotropy. Furthermore, microscale ligand anisotropy dominantly activates the host macrophage adhesion and pro-regenerative M2 polarization in vivo over the nanoscale ligand anisotropy, which can be cyclically reversed by substrate-proximate versus substrate-distant magnetic manipulation. This unprecedented scale-specific regulation of cells can be diversified by unlimited tuning of the scale, anisotropy, dimension, shape, and magnetism of hierarchical structures to decipher scale-specific dynamic cell-material interactions to advance immunoengineering strategies.

Ultrasound Cavitation Enables Rapid, Initiator-Free Fabrication of Tough Anti-Freezing Hydrogels

Hydrogels are often synthesized with thermal or photo-initiated gelation, leaving alternative energy sources less explored. While ultrasound has been used for polymer synthesis and mechanochemistry, its application through cavitation for hydrogel synthesis as a constructive force is rare, and the underlying sonochemical mechanisms are poorly understood. Here, the application and mechanism of ultrasound cavitation for rapid, initiator-free, and oxygen-tolerant fabrication of tough anti-freezing hydrogels is reported. By incorporating polyol solvents and interpenetrating polymers into the gelling solution, radical generation is amplified and network formation is enhanced. Using tough polyacrylamide-alginate hydrogels as a model system, rapid gelation (as fast as 2 minutes) and high fracture toughness (up to 600 J m- 2) is demonstrated. By varying ultrasound intensity, crosslinker-to-monomer ratio, and glycerol concentration, the synthesis-structure-property relation is established for the resulting sonogels and the underlying mechanism is uncovered using combined molecular, optical, and mechanical testing techniques. The coupling of gelation and convection under ultrasound results in sonogels with unique structural and mechanical properties. Additionally, the fabrication of hydrogel constructs is demonstrated using both non-focused and high-intensity focused ultrasound. This work establishes a foundation for ultrasound-driven sono-fabrication and highlights new avenues in soft materials, advanced manufacturing, bioadhesives, and tissue engineering.

Potentially commercializable nerve guidance conduits for peripheral nerve injury: Past, present, and future

Peripheral nerve injuries are a prevalent global issue that has garnered great concern. Although autografts remain the preferred clinical approach to repair, their efficacy is hampered by factors like donor scarcity. The emergence of nerve guidance conduits as novel tissue engineering tools offers a promising alternative strategy. This review aims to interpret nerve guidance conduits and their commercialization from both clinical and laboratory perspectives. To enhance comprehension of clinical situations, this article provides a comprehensive analysis of the clinical efficacy of nerve conduits approved by the United States Food and Drug Administration. It proposes that the initial six months post-transplantation is a critical window period for evaluating their efficacy. Additionally, this study conducts a systematic discussion on the research progress of laboratory conduits, focusing on biomaterials and add-on strategies as pivotal factors for nerve regeneration, as supported by the literature analysis. The clinical conduit materials and prospective optimal materials are thoroughly discussed. The add-on strategies, together with their distinct obstacles and potentials are deeply analyzed. Based on the above evaluations, the development path and manufacturing strategy for the commercialization of nerve guidance conduits are envisioned. The critical conclusion promoting commercialization is summarized as follows: 1) The optimization of biomaterials is the fundamental means; 2) The phased application of additional strategies is the emphasized direction; 3) The additive manufacturing techniques are the necessary tools. As a result, the findings of this research provide academic and clinical practitioners with valuable insights that may facilitate future commercialization endeavors of nerve guidance conduits.

3D-Bioprinting for Precision Microtissue Engineering: Advances, Applications, and Prospects

Microtissues, engineered to emulate the complexity of human organs, are revolutionizing the fields of regenerative medicine, disease modelling, and drug screening. Despite the promise of traditional microtissue engineering, it has yet to achieve the precision required to fully replicate organ-like structures. Enter 3D bioprinting, a transformative approach that offers unparalleled control over the microtissue's spatial arrangement and mechanical properties. This cutting-edge technology enables the detailed layering of bioinks, crafting microtissues with tissue-like 3D structures. It allows for the direct construction of organoids and the fine-tuning of the mechanical forces vital for tissue maturation. Moreover, 3D-printed devices provide microtissues with the necessary guidance and microenvironments, facilitating sophisticated tissue interactions. The applications of 3D-printed microtissues are expanding rapidly, with successful demonstrations of their functionality in vitro and in vivo. This technology excels at replicating the intricate processes of tissue development, offering a more ethical and controlled alternative to traditional animal models. By simulating in vivo conditions, 3D-printed microtissues are emerging as powerful tools for personalized drug screening, offering new avenues for pharmaceutical development and precision medicine.

Cellulose-based photo-curable chiral nematic ink for direct-ink-writing 3D printing

3D printing technology is one of the most promising strategies for constructing topological functional materials. The development of functional inks is a core issue in the technical development of 3D printing technology. In this study, we engineered photonic crystal inks based on chiral nematic liquid crystals of cellulose derivative, i.e. hydroxypropyl cellulose (HPC), and applied it to direct-ink-writing (DIW) 3D printing technology. We modified hydroxypropyl cellulose by etherification reaction to obtain photo-cross-linkable water-soluble hydroxypropyl cellulose acrylate (HPCA) with different degrees of substitution (DS). We comprehensively explored the effect of the DS on the initial concentration of formed chiral nematic liquid crystal and quantitatively, analyzed the relationship between the DS and the helical structure of the chiral nematic structure. We used photo cross-linkable chiral nematic HPCA as photonic crystal ink to construct structure-color 3D objects of diverse shapes. The constructed structure-color objects showcase robust tolerance against temperature and acidic conditions (pH = 1). Moreover, the color of the constructed objects is independent of the observation angle. The photonic crystal ink based on chiral nematic liquid crystals of biodegradable polysaccharide materials is expected to have excellent market prospects in the fields of such as smart packaging and optical devices.

Engineered Living Systems Based on Gelatin: Design, Manufacturing, and Applications

Engineered living systems (ELSs) represent purpose-driven assemblies of living components, encompassing cells, biomaterials, and active agents, intricately designed to fulfill diverse biomedical applications. Gelatin and its derivatives have been used extensively in ELSs owing to their mature translational pathways, favorable biological properties, and adjustable physicochemical characteristics. This review explores the intersection of gelatin and its derivatives with fabrication techniques, offering a comprehensive examination of their synergistic potential in creating ELSs for various applications in biomedicine. It offers a deep dive into gelatin, including its structures and production, sources, processing, and properties. Additionally, the review explores various fabrication techniques employing gelatin and its derivatives, including generic fabrication techniques, microfluidics, and various 3D printing methods. Furthermore, it discusses the applications of ELSs based on gelatin in regenerative engineering as well as in cell therapies, bioadhesives, biorobots, and biosensors. Future directions and challenges in gelatin fabrication are also examined, highlighting emerging trends and potential areas for improvements and innovations. In summary, this comprehensive review underscores the significance of gelatin-based ELSs in advancing biomedical engineering and lays the groundwork for guiding future research and developments within the field.

Mechanically Triggered Protein Desulfurization

The technology of native chemical ligation and postligation desulfurization has greatly expanded the scope of modern chemical protein synthesis. Here, we report that ultrasonic energy can trigger robust and clean protein desulfurization, and we developed an ultrasound-induced desulfurization (USID) strategy that is simple to use and generally applicable to peptides and proteins. The USID strategy involves a simple ultrasonic cleaning bath and an easy-to-use and easy-to-remove sonosensitizer, titanium dioxide. It features mild and convenient reaction conditions and excellent functional group compatibility, e.g., with thiazolidine (Thz) and serotonin, which are sensitive to other desulfurization strategies. The USID strategy is robust: without reoptimizing the reaction conditions, the same USID procedure can be used for the clean desulfurization of a broad range of proteins with one or more sulfhydryl groups, even in multi-hundred-milligram scale reactions. The utility of USID was demonstrated by the one-pot synthesis of bioactive cyclopeptides such as Cycloleonuripeptide E and Segetalin F, as well as convergent chemical synthesis of functionally important proteins such as histone H3.5 using Thz as a temporary protecting group. A mechanistic investigation indicated that USID proceeds via a radical-based mechanism promoted by low-frequency and low-intensity ultrasonication. Overall, our work introduces a mechanically triggered approach with the potential to become a robust desulfurization method for general use in chemical protein synthesis by both academic and industrial laboratories.

Emerging Wearable Acoustic Sensing Technologies

Sound signals not only serve as the primary communication medium but also find application in fields such as medical diagnosis and fault detection. With public healthcare resources increasingly under pressure, and challenges faced by disabled individuals on a daily basis, solutions that facilitate low-cost private healthcare hold considerable promise. Acoustic methods have been widely studied because of their lower technical complexity compared to other medical solutions, as well as the high safety threshold of the human body to acoustic energy. Furthermore, with the recent development of artificial intelligence technology applied to speech recognition, speech recognition devices, and systems capable of assisting disabled individuals in interacting with scenes are constantly being updated. This review meticulously summarizes the sensing mechanisms, materials, structural design, and multidisciplinary applications of wearable acoustic devices applied to human health and human-computer interaction. Further, the advantages and disadvantages of the different approaches used in flexible acoustic devices in various fields are examined. Finally, the current challenges and a roadmap for future research are analyzed based on existing research progress to achieve more comprehensive and personalized healthcare.

Optimizing the value of bioinks and robotics to advance in vivo bioprinting

In vivo bioprinting strategies aim at facilitating immediate integration of engineered tissues with the host's biological system. As integral parts of current bioprinting technologies, bioinks and robotics should be holistically considered for new biomedical applications. This implies that chosen bioinks should exhibit rheological properties that are compatible with the fabrication method and vice versa, bioprinting tools might need to be redesigned and reconstructed to fit the characteristics of the needed bioinks that after solidification act as supporting matrices for living cells. In this piece, we identify current challenges in merging the best of these two principles, we highlight relevant studies that have addressed this need, and we propose ideas how to approach this challenge in the next years.

Understanding the cellular dynamics, engineering perspectives and translation prospects in bioprinting epithelial tissues

The epithelium is one of the important tissues in the body as it plays a crucial barrier role serving as a gateway into and out of the body. Most organs in the body contain an epithelial tissue component, where the tightly connected, organ-specific epithelial cells organize into cysts, invaginations, or tubules, thereby performing distinct to endocrine or exocrine secretory functions. Despite the significance of epithelium, engineering functional epithelium in vitro has remained a challenge due to it is special architecture, heterotypic composition of epithelial tissues, and most importantly, difficulty in attaining the apico-basal and planar polarity of epithelial cells. Bioprinting has brought a paradigm shift in fabricating such apico-basal polarized tissues. In this review, we provide an overview of epithelial tissues and provide insights on recapitulating their cellular arrangement and polarization to achieve epithelial function. We describe the different bioprinting techniques that have been successful in engineering polarized epithelium, which can serve as in vitro models for understanding homeostasis and studying diseased conditions. We also discuss the different attempts that have been investigated to study these 3D bioprinted engineered epithelium for preclinical use. Finally, we highlight the challenges and the opportunities that need to be addressed for translation of 3D bioprinted epithelial tissues towards paving way for personalized healthcare in the future.

Jingle Cell Rock: Steering Cellular Activity With Low-Intensity Pulsed Ultrasound (LIPUS) to Engineer Functional Tissues in Regenerative Medicine

Acoustic manipulation or perturbation of biological soft matter has emerged as a promising clinical treatment for a number of applications within regenerative medicine, ranging from bone fracture repair to neuromodulation. The potential of ultrasound (US) endures in imparting mechanical stimuli that are able to trigger a cascade of molecular signals within unscathed cells. Particularly, low-intensity pulsed ultrasound (LIPUS) has been associated with bio-effects such as activation of specific cellular pathways and alteration of cell morphology and gene expression, the extent of which can be modulated by fine tuning of LIPUS parameters including intensity, frequency and exposure time. Although the molecular mechanisms underlying LIPUS are not yet fully elucidated, a number of studies clearly define the modulation of specific ultrasonic parameters as a means to guide the differentiation of a specific set of stem cells towards adult and fully differentiated cell types. Herein, we outline the applications of LIPUS in regenerative medicine and the in vivo and in vitro studies that have confirmed the unbounded clinical potential of this platform. We highlight the latest developments aimed at investigating the physical and biological mechanisms of action of LIPUS, outlining the most recent efforts in using this technology to aid tissue engineering strategies for repairing tissue or modelling specific diseases. Ultimately, we detail tissue-specific applications harnessing LIPUS stimuli, offering insights over the engineering of new constructs and therapeutic modalities. Overall, we aim to lay the foundation for a deeper understanding of the mechanisms governing LIPUS-based therapy, to inform the development of safer and more effective tissue regeneration strategies in the field of regenerative medicine.

All-Aqueous Embedded 3D Printing for Freeform Fabrication of Biomimetic 3D Constructs

All-aqueous embedded 3D printing, which involves extruding inks in an aqueous bath, has emerged as a transformative platform for the freeform fabrication of 3D constructs with precise control. The use of a supporting bath not only enables the printing of arbitrarily designed 3D constructs but also broadens ink selection for various soft matters, advancing the wide application of this technology. This review focuses on recent progress in the freeform preparation of 3D constructs using all-aqueous embedded 3D printing. It begins by discussing the significance of ultralow interfacial tension in all-liquid embedded printing and highlights the fundamental concepts and properties of all-aqueous system. The review then introduces recent advances in all-aqueous embedded 3D printing and clarifies the key factors affecting printing stability and shape fidelity, aiming to guide expansion and assessment of emerging printing systems used for various representative applications. Furthermore, it proposes the potential scope and applications of this technology, including in vitro models, cytomimetic microreactors, and soft ionic electronics. Finally, the review discusses the challenges facing current all-aqueous embedded 3D printing and offers future perspectives on possible improvements and developments.

Light-based 3D bioprinting techniques for illuminating the advances of vascular tissue engineering

Vascular tissue engineering faces significant challenges in creating in vitro vascular disease models, implantable vascular grafts, and vascularized tissue/organ constructs due to limitations in manufacturing precision, structural complexity, replicating the composited architecture, and mimicking the mechanical properties of natural vessels. Light-based 3D bioprinting, leveraging the unique advantages of light including high resolution, rapid curing, multi-material adaptability, and tunable photochemistry, offers transformative solutions to these obstacles. With the emergence of diverse light-based 3D bioprinting techniques and innovative strategies, the advances in vascular tissue engineering have been significantly accelerated. This review provides an overview of the human vascular system and its physiological functions, followed by an in-depth discussion of advancements in light-based 3D bioprinting, including light-dominated and light-assisted techniques. We explore the application of these technologies in vascular tissue engineering for creating in vitro vascular disease models recapitulating key pathological features, implantable blood vessel grafts, and tissue analogs with the integration of capillary-like vasculatures. Finally, we provide readers with insights into the future perspectives of light-based 3D bioprinting to revolutionize vascular tissue engineering.

Ultrasonication-Boosted Resorcinol-Formaldehyde Resin Nanoparticle Bromine Fixation and Corresponding Upgraded Aquatic Applications

Bromine (Br2) and related species removal from water systems are rather complicated due to the complicated chemistry instability, and materials with high Br2 removal rate and efficiency, along with stimuli/apparatus suitable for highly corrosive environments, are necessary. Ultrasonication as a non-destructive process is especially suitable in scenarios where conventional stir apparatus is not applicable, such as highly corrosive environments. Considering the validity nature of Br2 and combining the advantages of ultrasonic with a highly stable Br2 fixation method through aromatic polymer nanoparticles, we demonstrate highly efficient acoustic-aided Br2 removal in aqueous solutions with two times capacity compared to the non-treated sample. Related aquatic applications are also proposed for the materials to be cost-effective, including silver (Ag) recovery, recyclable MnO2-mediated Br2 deep removal, and aqueous zinc anode modification. The coupled novel-material-based processes motivate the strategic design of water purification with high-safety and sustainable industrial procedures and post-value-added utilizations.

The Assembly of Miniaturized Droplets toward Functional Architectures

Recent explorations of bioengineering have generated new concepts and strategies for the processing of soft and functional materials. Droplet assembly techniques can address problems in the construction of extremely soft architectures by expanding the manufacturing capabilities using droplets containing liquid or hydrogels including weak hydrogels. This Perspective sets out to provide a brief overview of this growing field, and discusses the challenges and opportunities ahead. The study highlights the recent key advances of materials and architectures from hitherto effective droplet-assembly technologies, as well as the applications in biomedical and bioengineering fields from artificial tissues to bioreactors. It is envisaged that these assembled architectures, as nature-inspired models, will stimulate the discovery of biomaterials and miniaturized platforms for interdisciplinary research in health, biotechnology, and sustainability.

Biofabrication and biomanufacturing in Ireland and the UK

As we navigate the transition from the Fourth to the Fifth Industrial Revolution, the emerging fields of biomanufacturing and biofabrication are transforming life sciences and healthcare. These sectors are benefiting from a synergy of synthetic and engineering biology, sustainable manufacturing, and integrated design principles. Advanced techniques such as 3D bioprinting, tissue engineering, directed assembly, and self-assembly are instrumental in creating biomimetic scaffolds, tissues, organoids, medical devices, and biohybrid systems. The field of biofabrication in the United Kingdom and Ireland is emerging as a pivotal force in bioscience and healthcare, propelled by cutting-edge research and development. Concentrating on the production of biologically functional products for use in drug delivery, in vitro models, and tissue engineering, research institutions across these regions are dedicated to innovating healthcare solutions that adhere to ethical standards while prioritising sustainability, affordability, and healthcare system benefits.

Graphic abstract

Straddling the Line Between In Vitro and Ex Vivo Investigations

Tissue engineering research fundamentally relies on experiments to advance knowledge, utilizing various models for research on both humans and animals. With scientific progress, experimental models have become increasingly complex over time. This complexity sometimes blurs the distinction between categories, making terminology less consistent. In biomedical research, three overarching terms are commonly used to characterize experimental environments: in vitro, ex vivo, and in vivo. While in vitro translates from Latin as "in glass," referring historically to experimental conditions in a test tube or petri dish, in vivo experiments occur within a living organism's natural environment. Conversely, ex vivo originates from living tissue outside its host environment while striving to maintain conditions as close to the host surroundings as possible. In the tissue engineering and regenerative medicine (TE&RM) community, there needs to be more clarity between in vitro and ex vivo terminology, with historical definitions sometimes disregarded and new terms often introduced without rigorous scientific justification. At this juncture, the question arises of when to refer to experiments as in vitro or ex vivo or whether the terms may be used synonymously in some instances. Moreover, what criteria must ex vivo experiments meet to be legitimately defined as such? This perspective is intended to address questions that would assist the TE&RM community in better understanding the differences between in vitro and ex vivo models. Impact Statement In the tissue engineering & regenerative medicine literature, the terms "in vitro" and "ex vivo" are often used interchangeably to describe experiments. This interchangeable usage can lead to a compromised interpretation of research results and, consequently, misleading scientific conclusions and teachings. This perspective aims to provide clarity on the various definitions of experimental designs. It also highlights the issue of using terms with inconsistent meanings that have origins dating back to the distant past. It's important to note that scientific definitions constantly evolve, and there is a scientifically rooted responsibility to evaluate and rethink the current state of affairs critically.

3D-Printed Hydrogels with Engineered Nanocrystalline Domains as Functional Vascular Constructs

Three-dimensionally printed (3DP) hydrogel-based vascular constructs have been investigated in response to the impaired function of blood vessels or organs by replicating exactly the 3D structural geometry to approach their function. However, they are still challenged by their intrinsic brittleness, which could not sustain the suture piercing and enable the long-term structural and functional stability during the direct contact with blood. Here, we reported the high-fidelity digital light processing (DLP) 3D printing of hydrogel-based vascular constructs from poly(vinyl alcohol)-based inks, followed by mechanical strengthening through engineering the nanocrystalline domains and subsequent surface modification. The as-prepared high-precision hydrogel vascular constructs were imparted with highly desirable mechanical robustness, suture tolerance, swelling resistance, antithrombosis, and long-term patency. Notably, the hydrogel-based bionic vein grafts, with precise valve structures, exhibited excellent control over the unidirectional flow and successfully fulfilled the biological functionalities and patency during a 4-week implantation within the deep veins of beagles, thus corroborating the promising potential for treating chronic venous insufficiency.

Solvent Engineering of Thermo-Responsive Hydrogels Facilitates Strong and Large Contractile Actuations

Thermo-responsive hydrogels can generate the actuation force through volumetric transitions in response to temperature changes. However, their weak mechanical properties and fragile actuation performance limit robust applications. Existing approaches to enhance these properties have typically depended on additional components, leading to an unavoidable interference to the actuation performance. In this work, robust thermo-responsive hydrogels are fabricated through solvent engineering. A particular solvent, N-methylformamide, interacts affinitively with the carbonyl group of N-isopropylacrylamide monomer, solubilizes the monomer with extremely high concentration, stabilizes chain propagation during polymerization, and greatly increases chain lengths and entanglements of the resulting polymer. The synthesized hydrogels are highly elastic, strong, and tough, displaying remarkable thermo-responsive contractile actuation. The simple synthetic process can broaden its applicability in designing robust functional hydrogel applications.

Regenerative cell therapy with 3D bioprinting

In situ additive biomanufacturing of structures may boost regenerative medicine.

Holographic direct sound printing

Direct sound printing (DSP), an alternative additive manufacturing process driven by sonochemical polymerization, has traditionally been confined to a single acoustic focal region, resulting in a voxel-by-voxel printing approach. To overcome this limitation, we introduce holographic direct sound printing (HDSP), where acoustic holograms, storing cross-sectional images of the desired parts, pattern acoustic waves to induce regional cavitation bubbles and on-demand regional polymerization. HDSP outperforms DSP in terms of printing speed by one order of magnitude and yields layerless printed structures. In our HDSP implementation, the hologram remains stationary while the printing platform moves along a three-dimensional path using a robotic arm. We present sono-chemiluminescence and high-speed imaging experiments to thoroughly investigate HDSP and demonstrate its versatility in applications such as remote ex-vivo in-body printing and complex robot trajectory planning. We showcase multi-object and multi-material printing and provide a comprehensive process characterization, including the effects of hologram design and manufacturing on the HDSP process, polymerization progression tracking, porosity tuning, and robotic trajectory computation. Our HDSP method establishes the integration of acoustic holography in DSP and related applications.

Enhancing Ultrasound Power Transfer: Efficiency, Acoustics, and Future Directions

Implantable medical devices (IMDs), like pacemakers regulating heart rhythm or deep brain stimulators treating neurological disorders, revolutionize healthcare. However, limited battery life necessitates frequent surgeries for replacements. Ultrasound power transfer (UPT) emerges as a promising solution for sustainable IMD operation. Current research prioritizes implantable materials, with less emphasis on sound field analysis and maximizing energy transfer during wireless power delivery. This review addresses this gap. A comprehensive analysis of UPT technology, examining cutting-edge system designs, particularly in power supply and efficiency is provided. The review critically examines existing efficiency models, summarizing the key parameters influencing energy transmission in UPT systems. For the first time, an energy flow diagram of a general UPT system is proposed to offer insights into the overall functioning. Additionally, the review explores the development stages of UPT technology, showcasing representative designs and applications. The remaining challenges, future directions, and exciting opportunities associated with UPT are discussed. By highlighting the importance of sustainable IMDs with advanced functions like biosensing and closed-loop drug delivery, as well as UPT's potential, this review aims to inspire further research and advancements in this promising field.

Bioinspired Flexible Hydrogelation with Programmable Properties for Tactile Sensing

Tactile sensing requires integrated detection platforms with distributed and highly sensitive haptic sensing capabilities along with biocompatibility, aiming to replicate the physiological functions of the human skin and empower industrial robotic and prosthetic wearers to detect tactile information. In this regard, short peptide-based self-assembled hydrogels show promising potential to act as bioinspired supramolecular substrates for developing tactile sensors showing biocompatibility and biodegradability. However, the intrinsic difficulty to modulate the mechanical properties severely restricts their extensive employment. Herein, by controlling the self-assembly of 9-fluorenylmethoxycarbonyl-modifid diphenylalanine (Fmoc-FF) through introduction of polyethylene glycol diacrylate (PEGDA), wider nanoribbons are achieved by untwisting from well-established thinner nanofibers, and the mechanical properties of the supramolecular hydrogels can be enhanced 10-fold, supplying bioinspired supramolecular encapsulating substrate for tactile sensing. Furthermore, by doping with poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and 9-fluorenylmethoxycarbonyl-modifid 3,4-dihydroxy-l-phenylalanine (Fmoc-DOPA), the Fmoc-FF self-assembled hydrogels can be engineered to be conductive and adhesive, providing bioinspired sensing units and adhesive layer for tactile sensing applications. Therefore, the integration of these modules results in peptide hydrogelation-based tactile sensors, showing high sensitivity and sustainable responses with intrinsic biocompatibility and biodegradability. The findings establish the feasibility of developing programmable peptide self-assembly with adjustable features for tactile sensing applications.

Advances in Cell-Rich Inks for Biofabricating Living Architectures

Advancing biofabrication toward manufacturing living constructs with well-defined architectures and increasingly biologically relevant cell densities is highly desired to mimic the biofunctionality of native human tissues. The formulation of tissue-like, cell-dense inks for biofabrication remains, however, challenging at various levels of the bioprinting process. Promising advances have been made toward this goal, achieving relatively high cell densities that surpass those found in conventional platforms, pushing the current boundaries closer to achieving tissue-like cell densities. On this focus, herein the overarching challenges in the bioprocessing of cell-rich living inks into clinically grade engineered tissues are discussed, as well as the most recent advances in cell-rich living ink formulations and their processing technologies are highlighted. Additionally, an overview of the foreseen developments in the field is provided and critically discussed.

3D Printing of Maturable Tissue Constructs Using a Cell‐Adaptable Nanocolloidal Hydrogel

3D‐printed cell‐laden hydrogels as tissue constructs show great promise in generating living tissues for medicine. Currently, the maturation of 3D‐printed constructs into living tissues remains challenge, since commonly used hydrogels struggle to provide an ideal microenvironment for the seeded cells. In this study, a cell‐adaptable nanocolloidal hydrogel is created for 3D printing of maturable tissue constructs. The nanocolloidal hydrogel is composed of interconnected nanoparticles, which is prepared by the self‐assembly and subsequent photocrosslinking of the gelatin methacryloyl solutions. Cells can get enough space to grow and migrate within the hydrogel through squeezing the flexible nanocolloidal networks. Meanwhile, the nanostructure can promote the seeded cells to proliferate and produce matrix proteins through mechanotransduction. Using digital light process‐based 3D printing technology, it can rapidly customize cartilage tissue constructs. After implantation, these tissue constructs efficiently matured into cartilage tissues for the articular cartilage defect repair and ear cartilage reconstruction in vivo. The 3D printing of maturable tissue constructs using the nanocolloidal hydrogel shows potential for future clinical applications.

4D bioprinting of programmed dynamic tissues

Setting time as the fourth dimension, 4D printing allows us to construct dynamic structures that can change their shape, property, or functionality over time under stimuli, leading to a wave of innovations in various fields. Recently, 4D printing of smart biomaterials, biological components, and living cells into dynamic living 3D constructs with 4D effects has led to an exciting field of 4D bioprinting. 4D bioprinting has gained increasing attention and is being applied to create programmed and dynamic cell-laden constructs such as bone, cartilage, and vasculature. This review presents an overview on 4D bioprinting for engineering dynamic tissues and organs, followed by a discussion on the approaches, bioprinting technologies, smart biomaterials and smart design, bioink requirements, and applications. While much progress has been achieved, 4D bioprinting as a complex process is facing challenges that need to be addressed by transdisciplinary strategies to unleash the full potential of this advanced biofabrication technology. Finally, we present future perspectives on the rapidly evolving field of 4D bioprinting, in view of its potential, increasingly important roles in the development of advanced dynamic tissues for basic research, pharmaceutics, and regenerative medicine.

(3D) Bioprinting-Next Dimension of the Pharmaceutical Sector

To create a review of the published scientific literature on the benefits and potential perspectives of the use of 3D bio-nitrification in the field of pharmaceutics. This work was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines for reporting meta-analyses and systematic reviews. The scientific databases PubMed, Scopus, Google Scholar, and ScienceDirect were used to search and extract data using the following keywords: 3D bioprinting, drug research and development, personalized medicine, pharmaceutical companies, clinical trials, drug testing. The data points to several aspects of the application of bioprinting in pharmaceutics were reviewed. The main applications of bioprinting are in the development of new drug molecules as well as in the preparation of personalized drugs, but the greatest benefits are in terms of drug screening and testing. Growth in the field of 3D printing has facilitated pharmaceutical applications, enabling the development of personalized drug screening and drug delivery systems for individual patients. Bioprinting presents the opportunity to print drugs on demand according to the individual needs of the patient, making the shape, structure, and dosage suitable for each of the patient's physical conditions, i.e., print specific drugs for controlled release rates; print porous tablets to reduce swallowing difficulties; make transdermal microneedle patches to reduce patient pain; and so on. On the other hand, bioprinting can precisely control the distribution of cells and biomaterials to build organoids, or an Organ-on-a-Chip, for the testing of drugs on printed organs mimicking specified disease characteristics instead of animal testing and clinical trials. The development of bioprinting has the potential to offer customized drug screening platforms and drug delivery systems meeting a range of individualized needs, as well as prospects at different stages of drug development and patient therapy. The role of bioprinting in preclinical and clinical testing of drugs is also of significant importance in terms of shortening the time to launch a medicinal product on the market.

Applications of Hydrogels in Osteoarthritis Treatment

This review critically evaluates advancements in multifunctional hydrogels, particularly focusing on their applications in osteoarthritis (OA) therapy. As research evolves from traditional natural materials, there is a significant shift towards synthetic and composite hydrogels, known for their superior mechanical properties and enhanced biodegradability. This review spotlights novel applications such as injectable hydrogels, microneedle technology, and responsive hydrogels, which have revolutionized OA treatment through targeted and efficient therapeutic delivery. Moreover, it discusses innovative hydrogel materials, including protein-based and superlubricating hydrogels, for their potential to reduce joint friction and inflammation. The integration of bioactive compounds within hydrogels to augment therapeutic efficacy is also examined. Furthermore, the review anticipates continued technological advancements and a deeper understanding of hydrogel-based OA therapies. It emphasizes the potential of hydrogels to provide tailored, minimally invasive treatments, thus highlighting their critical role in advancing the dynamic field of biomaterial science for OA management.

Self-enhancing sono-inks enable deep-penetration acoustic volumetric printing

Volumetric printing, an emerging additive manufacturing technique, builds objects with enhanced printing speed and surface quality by forgoing the stepwise ink-renewal step. Existing volumetric printing techniques almost exclusively rely on light energy to trigger photopolymerization in transparent inks, limiting material choices and build sizes. We report a self-enhancing sonicated ink (or sono-ink) design and corresponding focused-ultrasound writing technique for deep-penetration acoustic volumetric printing (DAVP). We used experiments and acoustic modeling to study the frequency and scanning rate-dependent acoustic printing behaviors. DAVP achieves the key features of low acoustic streaming, rapid sonothermal polymerization, and large printing depth, enabling the printing of volumetric hydrogels and nanocomposites with various shapes regardless of their optical properties. DAVP also allows printing at centimeter depths through biological tissues, paving the way toward minimally invasive medicine.