An oxygenating colloidal bioink for the engineering of biomimetic tissue constructs

Ensuring a sufficient oxygen supply is pivotal for the success of bioprinting applications since it fosters tissue integration and natural regeneration.Variation in oxygen concentration among diverse tissues necessitates the precise recreation of tissue-specific oxygen levels in imprinted constructs to support the survival of targeted cells.Although oxygen-releasing biomaterials,such as oxygen-generating microparticles(OMPs),have shown promise for enhancing the oxygen supply of microenvironments in injured tissues,whether this approach is scalable for large tissues and whether tissue-specific bioinks with varying OMP concentrations remain printable remain unknown.This study addresses this critical gap by introducing an innovative class of engineered oxygenated bioinks that combine colloidal-based microgels with OMPs.We report that incorporating nanosized calcium peroxide(nCaO_(2))and manganese oxide nanosheets(nMnO_(2))into hydrophobic polymeric microparticles enables precise modulation of oxygen release while controlling hydrogen peroxide release.Moreover,the fabrication of oxygenating and cytocompatible colloidal gels is achieved using an aqueous two-phase system.This study thoroughly evaluates the fundamental characteristics of the resulting bioink,including its rheological behaviors,printability,shape fidelity,mechanical properties,and oxygen release properties.Moreover,this study demonstrates the macroscopic scalability and cytocompatibility of printed constructs produced via cell-laden oxygenating colloidal bioinks.By showcasing the effectiveness of extrusion-based bioprinting,this study underscores how it can be used to fabricate biomimetic tissues,indicating its potential for new applications.The findings presented here advance the bioprinting field by achieving scalability with both high cell viability and the possibility of mimicking specifically oxygenated tissues.This work thereby offers a promising avenue for the development of functional tissues with enhanced physiological relevance.

From oral formulations to drug-eluting implants:using 3D and 4D printing to develop drug delivery systems and personalized medicine

Since the start of the Precision Medicine Initiative by the United States of America in 2015,interest in personalized medicine has grown extensively.In short,personalized medicine is a term that describes medical treatment that is tuned to the individual.One possible way to realize personalized medicine is 3D printing.When using materials that can be tuned upon stimulation,4D printing is established.In recent years,many studies have been exploring a new field that combines 3D and 4D printing with therapeutics.This has resulted in many concepts of pharmaceutical devices and formulations that can be printed and,possibly,tailored to an individual.Moreover,the first 3D printed drug,Spritam®,has already found its way to the clinic.This review gives an overview of various 3D and 4D printing techniques and their applications in the pharmaceutical field as drug delivery systems and personalized medicine.

Scalable fabrication,compartmentalization and applications of living microtissues

Living microtissues are used in a multitude of applications as they more closely resemble native tissue physiology,as compared to 2D cultures.Microtissues are typically composed of a combination of cells and materials in varying combinations,which are dictated by the applications’design requirements.Their applications range wide,from fundamental biological research such as differentiation studies to industrial applications such as cruelty-free meat production.However,their translation to industrial and clinical settings has been hindered due to the lack of scalability of microtissue production techniques.Continuous microfluidic processes provide an opportunity to overcome this limitation as they offer higher throughput production rates as compared to traditional batch techniques,while maintaining reproducible control over microtissue composition and size.In this review,we provide a comprehensive overview of the current approaches to engineer microtissues with a focus on the advantages of,and need for,the use of continuous processes to produce microtissues in large quantities.Finally,an outlook is provided that outlines the required developments to enable large-scale microtissue fabrication using continuous processes.

Enzymatic co-crosslinking of star-shaped poly(ethylene glycol)tyramine and hyaluronic acid tyramine conjugates provides elastic biocompatible and biodegradable hydrogels

A combination of the viscoelastic properties of hyaluronic acid(HA)and the elastic properties of star shaped 8-arm poly(ethylene glycol)(8-arm PEG)was used to design in-situ forming hydrogels.Hydrogels were prepared by the enzymatic crosslinking of a partially tyramine modified 8-arm PEG and a tyramine conjugated HA using horseradish peroxidase in the presence of hydrogen peroxide.Hydrogels of the homopolymer conjugates and mixtures thereof were rapidly formed within seconds under physiological conditions at low polymer and enzyme concentrations.Elastic hydrogels with high gel content(≥95%)and high storage moduli(up to 22.4 kPa)were obtained.An in vitro study in the presence of hyaluronidase(100 U/mL)revealed that with increasing PEG content the degradation time of the hybrid hydrogels increased up to several weeks,whereas hydrogels composed of only hyaluronic acid degraded within 2 weeks.Human mesenchymal stem cells(hMSCs)incorporated in the hybrid hydrogels remained viable as shown by a PrestoBlue and a live-dead assay,confirming the biocompatibility of the constructs.The production of an extracellular matrix by re-differentiation of encapsulated human chondrocytes was followed over a period of 28 days.Gene expression indicated that these highly elastic hydrogels induced an enhanced production of collagen type II.At low PEG-TA/HA-TA ratios a higher expression of SOX 9 and ACAN was observed.These results indicate that by modulating the ratio of PEG/HA,injectable hydrogels can be prepared applicable as scaffolds for tissue regeneration applications.