4D Printing: The Development of Responsive Materials Using 3D-Printing Technology

4D printing chemical stimuli-responsive hydrogels for tissue engineering and localized drug delivery applications - part 2

INTRODUCTION

The incorporation of 4D printing alongside chemical stimuli-responsive hydrogels represents a significant advancement in the field of biomedical engineering, effectively overcoming the constraints associated with conventional static 3D-printed structures. Through the integration of time as the fourth dimension, 4D printing facilitates the development of dynamic and adaptable structures that can react to chemical alterations in their surroundings. This innovation presents considerable promise for sophisticated tissue engineering and targeted drug delivery applications.

AREAS COVERED

This review examines the function of chemical stimuli-responsive hydrogels within the context of 4D printing, highlighting their distinctive ability to undergo regulated transformations when exposed to particular chemical stimuli. An in-depth examination of contemporary research underscores the collaborative dynamics between these hydrogels and their surroundings, focusing specifically on their utilization in biomimetic scaffolds for tissue regeneration and the advancement of intelligent drug delivery systems.

EXPERT OPINION

The integration of 4D printing technology with chemically responsive hydrogels presents exceptional prospects for advancements in tissue engineering and targeted drug delivery, facilitating the development of personalized and adaptive medical solutions. Although the potential is promising, it is essential to address challenges such as material optimization, biocompatibility, and precise control over stimuli-responsive behavior to facilitate clinical translation and scalability.

3D printed reservoir-like vaginal rings for antibiotic delivery

Targeting the development of 3D printed reservoir-like vaginal rings (VRs) intended to fulfill the needs of precision medicine, prototypes ensuring prolonged release of metronidazole (MTZ) were preliminary manufactured and tested. Indeed, this drug represents the first-line therapy against bacterial vaginosis, which would especially benefit from convenient as well as easy dose adjustment and from more than 48 h continuous release, thus avoiding barely tolerated and repeated administrations. Starting from a soft thermoplastic elastomer (TPE), hollow ring structures were successfully printed at 190 °C and then extemporaneously filled with drug-loaded, in-situ-crosslinking hydrogel formulations based on alginate (ALG). 3 VR designs, differing in dimensions, number of open surfaces as well as in relevant areas were investigated, together with 9 drug-saturated hydrogel formulations containing extra suspended MTZ particles (20-50 %) and increasing ALG concentrations (2-6 %). Manufacturing of final rings was fine-tuned based on materials thermo-mechanical properties. For comparison purposes, hydrogels with analogous composition were either cast using purposely developed molds or 3D printed mimicking the ring design. VR release performance turned out dependent on the drug solubility and on the surface area available for hydrogel contact with vaginal fluids. Interestingly, this surface resulted correlated to both the outer and inner structure of the system. The data collected would provide an effective asset to increase the versatility of reservoir-like VRs, making them a powerful tool towards therapy customization.

From lab to life: advances inin-situbioprinting and bioink technology

Bioprinting has the potential to revolutionize tissue engineering and regenerative medicine, offering innovative solutions for complex medical challenges and addressing unmet clinical needs. However, traditionalin vitrobioprinting techniques face significant limitations, including difficulties in fabricating and implanting scaffolds with irregular shapes, as well as limited accessibility for rapid clinical application. To overcome these challenges,in-situbioprinting has emerged as a groundbreaking approach that enables the direct deposition of cells, biomaterials, and bioactive factors onto damaged organs or tissues, eliminating the need for pre-fabricated 3D constructs. This method promises a personalized, patient-specific approach to treatment, aligning well with the principles of precision medicine. The success ofin-situbioprinting largely depends on the advancement of bioinks, which are essential for maintaining cell viability and supporting tissue development. Recent innovations in hand-held bioprinting devices and robotic arms have further enhanced the flexibility ofin-situbioprinting, making it applicable to various tissue types, such as skin, hair, muscle, bone, cartilage, and composite tissues. This review examinesin-situbioprinting techniques, the development of smart, multifunctional bioinks, and their essential properties for promoting cell viability and tissue growth. It highlights the versatility and recent advancements inin-situbioprinting methods and their applications in regenerating a wide range of tissues and organs. Furthermore, it addresses the key challenges that must be overcome for broader clinical adoption and propose strategies to advance these technologies toward mainstream medical practice.

Calcium Cross-Linked Cellulose Nanofibrils: Hydrogel Design for Local and Controlled Nitric Oxide Release

Nitric oxide (NO) holds promise for wound healing due to its antimicrobial properties and role in promoting vasodilation and tissue regeneration. The local delivery of NO to target cells or organs offers significant potential in numerous biomedical applications, especially when NO donors are integrated into nontoxic viscous matrices. This study presents the development of robust cellulose nanofibril (CNF) hydrogels designed to control the release of nitric oxide (NO) generated in situ from a NO-donor molecule (S-nitrosoglutathione, GSNO) obtained from the nitrosation of its precursor molecule glutathione (GSH). CNF, efficiently isolated from sugar cane bagasse, exhibited a high aspect ratio and excellent colloidal stability in water. Although depletion forces could be observed upon the addition of GSH, this effect did not significantly alter the morphology of the CNF network at low GSH concentrations (<20 mM). Ionic cross-linking with Ca2+ resulted in nontoxic and robust hydrogels (elastic moduli ranging from 300 to 3000 Pa) at low CNF solid content. The release rate of NO from GSNO decreased in CNF from 1.61 to 0.40 mmol. L-1·h-1 when the nanofibril content raised from 0.3 to 1.0 wt %. The stabilization effect monitored for 16 h was assigned to hydrogel mesh size, which was easily tailored by modifying the concentration of CNF in the initial suspension. These results highlight the potential of CNF-based hydrogels in biomedical applications requiring a precise NO delivery.

3D and 4D printing of MXene-based composites: from fundamentals to emerging applications

The advent of three-dimensional (3D) and four-dimensional (4D) printing technologies has significantly improved the fabrication of advanced materials, with MXene-based composites emerging as a particularly promising class due to their exceptional electrical, mechanical, and chemical properties. This review explores the fundamentals of MXenes and their composites, examining their unique characteristics and the underlying principles of their synthesis and processing. We highlight the transformative potential of 3D and 4D printing techniques in tailoring MXene-based materials for a wide array of applications. In the field of tissue regeneration, MXene composites offer enhanced biocompatibility and mechanical strength, making them ideal for scaffolds and implants. For drug delivery, the high surface area and tunable surface chemistry of MXenes enable precise control over drug release profiles. In energy storage, MXene-based electrodes exhibit superior conductivity and capacity, paving the way for next-generation batteries and supercapacitors. Additionally, the sensitivity and selectivity of MXene composites make them excellent candidates for various (bio)sensing applications, from environmental monitoring to biomedical diagnostics. By integrating the dynamic capabilities of 4D printing, which introduces time-dependent shape transformations, MXene-based composites can further adapt to complex and evolving functional requirements. This review provides a comprehensive overview of the current state of research, identifies key challenges, and discusses future directions for the development and application of 3D and 4D printed MXene-based composites. Through this exploration, we aim to underscore the significant impact of these advanced materials and technologies on diverse scientific and industrial fields.

Design of nanosystems for melanoma treatment

Melanoma is a prevalent and concerning form of skin cancer affecting millions of individuals worldwide. Unfortunately, traditional treatments can be invasive and painful, prompting the need for alternative therapies with improved efficacy and patient outcomes. Nanosystems offer a promising solution to these obstacles through the rational design of nanoparticles (NPs) which are structured into nanocomposite forms, offering efficient approaches to cancer treatment procedures. A range of NPs consisting of polymeric, metallic and metal oxide, carbon-based, and virus-like NPs have been studied for their potential in treating skin cancer. This review summarizes the latest developments in functional nanosystems aimed at enhancing melanoma treatment. The fundamentals of these nanosystems, including NPs and the creation of various functional nanosystem types, facilitating melanoma treatment are introduced. Then, the advances in the applications of functional nanosystems for melanoma treatment are summarized, outlining both their benefits and the challenges encountered in implementing nanosystem therapies.

Enhancing Short-Range Interactions to Broaden the Temperature Range for Coexistence of Antiferroelectricity and Ferroelasticity

Antiferroelectric (AFE) materials, characterized by double electric hysteresis loops, can be transformed to the ferroelectric (FE) phase under an external electric field, making them promising candidates for electronic energy storage and solid-state refrigeration. Additionally, the field-induced strain in AFE materials is contingent upon the direction of the electric field, rendering it with a switching characteristic. Although AFE materials have made progress in the field of energy storage and negative electrocaloric effect, the coexistence of AFE and ferroelasticity is still rarely reported. Here, two isomorphic organic-inorganic hybrid perovskites, HDAEPbCl4 and HDAEPbBr4 (HDAE is [2-(hydroxydimethylammonio)ethan-1-aminium]), exhibiting FE-AFE-PE (PE is paraelectric) phase transitions, are presented. Remarkably, the temperature range where AFE and ferroelasticity coexist is significantly broadened from 59.9 K to 115.1 K by strengthening short-range forces via halogen substitution. This discovery extends the family of FE, AFE, and ferroelastic materials, contributing to the development of multifunctional materials and advancing multifunctional material development.

Dual-functional Hydroxyapatite scaffolds for bone regeneration and precision drug delivery

Addressing infected bone defects remains a significant challenge in orthopedics, requiring effective infection control and bone defect repair. A promising therapeutic approach involves the development of dual-functional engineered biomaterials with drug delivery systems that combine antibacterial properties with osteogenesis promotion. The Hydroxyapatite composite scaffolds offer a one-stage treatment, eliminating the need for multiple surgeries and thereby streamlining the process and reducing treatment time. This review delves into the impaired bone repair mechanisms within pathogen-infected and inflamed microenvironments, providing a theoretical foundation for treating infectious bone defects. Additionally, it explores composite scaffolds made of antibacterial and osteogenic materials, along with advanced drug delivery systems that possess both antibacterial and bone-regenerative properties. By offering a comprehensive understanding of the microenvironment of infectious bone defects and innovative design strategies for dual-function scaffolds, this review presents significant advancements in treatment methods for infectious bone defects. Continued research and clinical validation are essential to refine these innovations, ensuring biocompatibility and safety, achieving controlled release and stability, and developing scalable manufacturing processes for widespread clinical application.

Drug-Loaded Bioscaffolds for Osteochondral Regeneration

Osteochondral defect is a complex tissue loss disease caused by arthritis, high-energy trauma, and many other reasons. Due to the unique structural characteristics of osteochondral tissue, the repair process is sophisticated and involves the regeneration of both hyaline cartilage and subchondral bone. However, the current clinical treatments often fall short of achieving the desired outcomes. Tissue engineering bioscaffolds, especially those created via three-dimensional (3D) printing, offer promising solutions for osteochondral defects due to their precisely controllable 3D structures. The microstructure of 3D-printed bioscaffolds provides an excellent physical environment for cell adhesion and proliferation, as well as nutrient transport. Traditional 3D-printed bioscaffolds offer mere physical stimulation, while drug-loaded 3D bioscaffolds accelerate the tissue repair process by synergistically combining drug therapy with physical stimulation. In this review, the physiological characteristics of osteochondral tissue and current treatments of osteochondral defect were reviewed. Subsequently, the latest progress in drug-loaded bioscaffolds was discussed and highlighted in terms of classification, characteristics, and applications. The perspectives of scaffold design, drug control release, and biosafety were also discussed. We hope this article will serve as a valuable reference for the design and development of osteochondral regenerative bioscaffolds and pave the way for the use of drug-loaded bioscaffolds in clinical therapy.

Polyvinyl alcohol-based capsule shells manufactured by injection molding as ready-to-use moisture barriers for the development of delivery systems

In this work, feasibility of injection molding was demonstrated for manufacturing capsule shells. 600 µm-thick prototypes were successfully molded with pharmaceutical-grade low-viscosity polyvinyl alcohols (PVAs), possibly added with a range of different fillers. They showed reproducible weight and thickness (CV < 2 and 5, respectively), compliant behavior upon piercing (holes diameter analogous to the reference), tunable release performance (immediate and pulsatile), and moisture protection capability. To assess the latter, an on-line method relying on near infrared spectroscopy measurements was set-up and validated. Based on the data collected and considering the versatility IM would provide for product shape/thickness/composition, PVA-based molded shells could help widening the portfolio of ready-to-use capsules, representing an interesting alternative to those commercially available. Indeed, these capsules could be filled with various formulations, even those with stability issues, and intended either for oral administration or for pulmonary delivery via single-dose dry powder inhalers.

Recent Advances in the Application of 3D-Printing Bioinks Based on Decellularized Extracellular Matrix in Tissue Engineering

In recent years, 3D bioprinting with various types of bioinks has been widely used in tissue engineering to fabricate human tissues and organs with appropriate biological functions. Decellularized extracellular matrix (dECM) is an excellent bioink candidate because it is enriched with a variety of bioactive proteins and bioactive factors and can provide a suitable environment for tissue repair or tissue regeneration while reducing the likelihood of severe immune rejection. In this Review, we systematically review recent advances in 3D bioprinting and decellularization technologies and comprehensively detail the latest research and applications of dECM as a bioink for tissue engineering in various systems, with the aim of providing a reference for researchers in tissue engineering to better understand the properties of dECM bioinks.

Biopolymers Take Center Stage in Wound Healing Advancements

The human body possesses a remarkable ability to heal itself from injuries [...].

Novel Drug Delivery Systems: An Important Direction for Drug Innovation Research and Development

The escalating demand for enhanced therapeutic efficacy and reduced adverse effects in the pharmaceutical domain has catalyzed a new frontier of innovation and research in the field of pharmacy: novel drug delivery systems. These systems are designed to address the limitations of conventional drug administration, such as abbreviated half-life, inadequate targeting, low solubility, and bioavailability. As the disciplines of pharmacy, materials science, and biomedicine continue to advance and converge, the development of efficient and safe drug delivery systems, including biopharmaceutical formulations, has garnered significant attention both domestically and internationally. This article presents an overview of the latest advancements in drug delivery systems, categorized into four primary areas: carrier-based and coupling-based targeted drug delivery systems, intelligent drug delivery systems, and drug delivery devices, based on their main objectives and methodologies. Additionally, it critically analyzes the technological bottlenecks, current research challenges, and future trends in the application of novel drug delivery systems.

Do medical devices contribute to sustainability? The role of innovative polymers and device design

Sustainability of a medical device has not yet become a major issue in public discussions compared to other topics with impact to material performance, clinical application, production economy and environmental pollution. Due to their unique properties, polymers (plastics) allow for multiple, flexible applications in medical device technology. Polymers are part of the majority of disposable and single use medical device and contribute with 3% to the worldwide production of plastics. The global medical polymer market size was valued 19.9 billion US-$ in 2022 and its value projection for 2023 is expected to reach 43.03 billion US-$ Here, a wider concept of related sustainability is introduced for medical devices and their polymer components. A close look on medical device specification reveals that additional properties are required to provide sustainability, such as biodegradability, quality by device design (QbD), as well as an inbuild performance service for patients, healthcare professionals and healthcare providers. The increasing global numbers for chronic and non-communicable diseases require a huge demand for single use medical devices. A careful look at polymer specification and its performance properties is needed, including possible chemical modifications and degradation processes during waste disposal. Bioengineers in charge of design and production of medical devices will only be successful when they apply a holistic and interdisciplinary approach to medical device sustainability.

Exploring the Horizons of Four-Dimensional Printing Technology in Dentistry

In dentistry, the integration of additive manufacturing, particularly 3D printing, has marked significant progress. However, the emergence of 4D printing, which allows materials to change shape dynamically in response to stimuli, opens up new avenues for innovation. This review sheds light on recent advancements and potential applications of 4D printing in dentistry, delving into the fundamental principles and materials involved. It emphasizes the versatility of shape-changing polymers and composites, highlighting their ability to adapt dynamically. Furthermore, the review explores the challenges and opportunities in integrating 4D printing into dental practice, including the customization of dental prosthetics, orthodontic devices, and drug delivery systems and also probing into the potential benefits of utilizing stimuli-responsive materials to improve patient comfort, treatment outcomes, and overall efficiency and the review discusses current limitations and future directions, emphasizing the importance of standardized fabrication techniques, biocompatible materials, and regulatory considerations. Owing to its diverse applications and advantages, 4D printing technology is poised to transform multiple facets of dental practice, thereby fostering the development of healthcare solutions that are more tailored, effective, and centered around patient needs.

Review of Spider Silk Applications in Biomedical and Tissue Engineering

This review will present the latest research related to the production and application of spider silk and silk-based materials in reconstructive and regenerative medicine and tissue engineering, with a focus on musculoskeletal tissues, and including skin regeneration and tissue repair of bone and cartilage, ligaments, muscle tissue, peripheral nerves, and artificial blood vessels. Natural spider silk synthesis is reviewed, and the further recombinant production of spider silk proteins. Research insights into possible spider silk structures, like fibers (1D), coatings (2D), and 3D constructs, including porous structures, hydrogels, and organ-on-chip designs, have been reviewed considering a design of bioactive materials for smart medical implants and drug delivery systems. Silk is one of the toughest natural materials, with high strain at failure and mechanical strength. Novel biomaterials with silk fibroin can mimic the tissue structure and promote regeneration and new tissue growth. Silk proteins are important in designing tissue-on-chip or organ-on-chip technologies and micro devices for the precise engineering of artificial tissues and organs, disease modeling, and the further selection of adequate medical treatments. Recent research indicates that silk (films, hydrogels, capsules, or liposomes coated with silk proteins) has the potential to provide controlled drug release at the target destination. However, even with clear advantages, there are still challenges that need further research, including clinical trials.