Hydrogel-Encapsulated Engineered Microbial Consortium as a Photoautotrophic "Living Material" for Promoting Skin Wound Healing

Adaptations of Gram-Negative and Gram-Positive Probiotic Bacteria in Engineered Living Materials

Encapsulation of microbes in natural or synthetic matrices is a key aspect of engineered living materials, although the influence of such confinement on microbial behavior is poorly understood. A few recent studies have shown that the spatial confinement and mechanical properties of the encapsulating material significantly influence microbial behavior, including growth, metabolism, and gene expression. However, comparative studies within different bacterial species under identical confinement conditions are limited. In this study, Gram-negative Escherichia coli Nissle 1917 and Gram-positive Lactiplantibacillus plantarum WCFS1 were encapsulated in hydrogel matrices, and their growth, metabolic activity, and recombinant gene expression were examined under varying degrees of hydrogel stiffness, achieved by adjusting the polymer concentration and chemical cross-linking. Both bacteria grow from single cells into confined colonies, but more interestingly, in E. coli gels, mechanical properties influenced colony growth, size, and morphology, whereas this did not occur in L. plantarum gels. However, with both bacteria, increased matrix stiffness led to higher levels of recombinant protein production within the colonies. By measuring metabolic heat from the bacterial gels using the isothermal microcalorimetry technique, it was inferred that E. coli adapts to the mechanical restrictions through multiple metabolic transitions and is significantly affected by the different hydrogel properties. Contrastingly, both of these aspects were not observed with L. plantarum. These results revealed that despite both bacteria being gut-adapted probiotics with similar geometries, mechanical confinement affects them considerably differently. The weaker influence of matrix stiffness on L. plantarum is attributed to its slower growth and thicker cell wall, possibly enabling the generation of higher turgor pressures to overcome restrictive forces under confinement. By providing fundamental insights into the interplay between mechanical forces and bacterial physiology, this work advances our understanding of how matrix properties shape bacterial behavior. The implications of these findings will aid the design of engineered living materials for therapeutic applications.

Preclinical Assessment of Living Therapeutic Materials: State-of-Art and Challenges

Living Therapeutic Materials represent a promising technology to tackle therapeutic problems that classical materials cannot address. Despite the advancements on new functions of these devices, new applications, and new fabrication methods, the preclinical evaluation of Living Therapeutic Materials is still very limited and new challenges appear when incorporating the living devices in contact with the host. This is a critical bottleneck in the path to translation to the clinic. Therefore, we have compiled the literature on Living Therapeutic Materials, with a focus on microorganism-based living therapeutic materials, and summarized the investigations carried out to assess their biocompatibility, safety, and efficacy. We have split the investigations in three parts: in vitro, ex vivo, and in vivo assessments, where we describe common practices and remaining challenges.

Engineered microbial living matter for diagnostics, prevention, and therapy

Living therapeutic and diagnostic materials based on engineered microorganisms are emerging as a novel approach with the perspective of providing patient-tailored, sustainable, and cost-effective healthcare solutions. In this review, we focus on recent advances in using genetically or chemically engineered microorganisms as living diagnostics, therapeutics, and as a means of prevention for various diseases. We also highlight the applications of living therapeutics for acute and chronic diseases, and the role of micro/macro-encapsulation of the engineered microorganisms. We further showcase the current success of engineered living therapeutics in clinical trials and discuss challenges and future trends in the field.

A Narrative Review of Bioactive Hydrogel Microspheres: Ingredients, Modifications, Fabrications, Biological Functions, and Applications

Hydrogel microspheres are important in regenerative medicine and tissue engineering, acting as cargos of cells, drugs, growth factors, bio-inks for 3D printing, and medical devices. The antimicrobial and anti-inflammatory characteristics of hydrogel microspheres are good for treating injured tissues. However, the biological properties of hydrogel microspheres should be modified for optimal treatment of various body parts with different physiological and biochemical environments. In addition, specific preparation methods are required to produce customized hydrogel microspheres with different shapes and sizes for various clinical applications. Herein, the advances in hydrogel microspheres for biomedical applications are reviewed. Synthesis methods for hydrogel precursor solutions, manufacturing methods, and strategies for enhancing the biological functions of these hydrogel microspheres are described. The involvement of bioactive hydrogel microspheres in tissue repair is also discussed. This review anticipates fostering more insights into the design, production, and application of hydrogel microspheres in biomedicine.

Engineered bacteria launch and control an oncolytic virus

The ability of bacteria and viruses to selectively replicate in tumors has led to synthetic engineering of new microbial therapies. Here we design a cooperative strategy whereby S. typhimurium bacteria transcribe and deliver the Senecavirus A RNA genome inside host cells, launching a potent oncolytic viral infection. "Encapsidated" by bacteria, the viral genome can further bypass circulating antiviral antibodies to reach the tumor and initiate replication and spread within immune mice. Finally, we engineer the virus to require a bacterially delivered protease to achieve virion maturation, demonstrating bacterial control over the virus. This work extends bacterially delivered therapeutics to viral genomes, and shows how a consortium of microbes can achieve a cooperative aim.

Advances in the preparation, applications, challenges, and future trends of polysaccharide-based gels as food-grade delivery systems for probiotics: A review

Probiotics are highly regarded for their multiple functions, such as regulating gut health, enhancing the immune system, and preventing chronic diseases. However, their stability in harsh environments and targeted release remain significant challenges. Therefore, exploring effective protection and delivery strategies to ensure targeted release of probiotics is critically important. Polysaccharides, known for their non-toxicity, excellent biocompatibility, and superior biodegradability, show broad prospects in probiotic delivery by forming physical barriers to protect the probiotics. Particularly, polysaccharide-based gels (PBGs), with their unique "spider-web" like structure, capture and ensure the targeted release of probiotics, significantly enhancing their efficacy. This review discusses common polysaccharides used in PBG preparation, their classification and synthesis in food applications, and the advantages of PBGs as probiotic delivery systems. Despite their potential, challenges such as inconsistent gel properties and the need for improved stability remain. Future research should focus on developing novel PBG materials with higher biodegradability and mechanical strength, optimizing the physicochemical properties and cross-linking methods, as well as designing multilayered structures for more precise release control. Additionally, exploring the co-delivery of probiotics with prebiotics, active ingredients, or multi-strain systems could further enhance the efficacy of probiotic delivery.

Engineered bacterial therapeutics with material solutions

Recent advances in engineered bacterial therapeutics underscore their potential in treating diseases via targeted, live interventions. Despite their promising performance in early clinical phases, no engineered therapeutic bacteria have yet received approval, primarily due to challenges in proving efficacy while ensuring biosafety. Material science innovations, particularly the encapsulation of bacteria within hydrogels, present a promising avenue to enhance bacterial survival, efficacy, and safety in therapeutic applications. This review discusses this interdisciplinary approach to develop living therapeutic materials. Hydrogels not only safeguard the bacteria from harsh physiological conditions but also enable controlled therapeutic release and prevent unintended bacterial dissemination. The strategic use of encapsulation materials could redefine the delivery and functionality of engineered bacterial therapeutics, facilitating their clinical translation.

Bacterial live therapeutics for human diseases

The genomic revolution has fueled rapid progress in synthetic and systems biology, opening up new possibilities for using live biotherapeutic products (LBP) to treat, attenuate or prevent human diseases. Among LBP, bacteria-based therapies are particularly promising due to their ability to colonize diverse human tissues, modulate the immune system and secrete or deliver complex biological products. These bacterial LBP include engineered pathogenic species designed to target specific diseases, and microbiota species that promote microbial balance and immune system homeostasis, either through local administration or the gut-body axes. This review focuses on recent advancements in preclinical and clinical trials of bacteria-based LBP, highlighting both on-site and long-reaching strategies.

Assembly of functional microbial ecosystems: from molecular circuits to communities

Microbes compete and cooperate with each other via a variety of chemicals and circuits. Recently, to decipher, simulate, or reconstruct microbial communities, many researches have been engaged in engineering microbiomes with bottom-up synthetic biology approaches for diverse applications. However, they have been separately focused on individual perspectives including genetic circuits, communications tools, microbiome engineering, or promising applications. The strategies for coordinating microbial ecosystems based on different regulation circuits have not been systematically summarized, which calls for a more comprehensive framework for the assembly of microbial communities. In this review, we summarize diverse cross-talk and orthogonal regulation modules for de novo bottom-up assembling functional microbial ecosystems, thus promoting further consortia-based applications. First, we review the cross-talk communication-based regulations among various microbial communities from intra-species and inter-species aspects. Then, orthogonal regulations are summarized at metabolites, transcription, translation, and post-translation levels, respectively. Furthermore, to give more details for better design and optimize various microbial ecosystems, we propose a more comprehensive design-build-test-learn procedure including function specification, chassis selection, interaction design, system build, performance test, modeling analysis, and global optimization. Finally, current challenges and opportunities are discussed for the further development and application of microbial ecosystems.

Engineering Robust Silver-Decorated calcium peroxide Nano-Antibacterial Platforms for chemodynamic enhanced sterilization

Calcium peroxide (CaO2) is commonly used as a hydrogen peroxide (H2O2) donor to eliminate bacterial infections. However, the rapid dissociation of CaO2 and the explosive release of H2O2 have limited the development of CaO2 in the antibacterial field. Therefore, a series of silver nanoparticles (AgNPs) functionalized bacteria-triggered smart hydrogels (CSA-H) that integrate sustained release of nanoparticles and localized chemodynamic sterilization were constructed. The pH-responsive hydrogel formed through the Schiff base reaction enables the responsive release of CaO2 nanoparticles while simultaneously regulating the concentration of H2O2 within the bacterial infection microenvironment. AgNPs are capable of reacting with H2O2 under mildly acidic conditions to produce hydroxyl radicals with enhanced antimicrobial activity. The antimicrobial results demonstrated that AgNPs functionalized silicon dioxide-coated calcium peroxide (CaO2@SiO2/AgNPs) nanoparticles exhibited enhanced bactericidal activity compared to AgNPs or CaO2 alone. Furthermore, CSA-H hydrogels exhibited significant antibacterial activity against S. aureus and E. coli under the dual effect of AgNPs and pH-driven Fenton-like reactions. This chemodynamic antibacterial platform is environmentally responsive and provides a promising strategy for creating multifunctional hydrogels loaded with nano-enzymes, thus advancing the development of AgNPs in chemodynamic-antibacterial related applications.

Living Engineered Bacterial Therapeutics: Emerging Affordable Precision Interventions

Live biotherapeutic products (LBPs), including engineered bacteria, are rapidly emerging as potential therapeutic interventions. These innovative therapies can serve as live in situ drug delivery platforms for the direct deposition of therapeutic payloads, including complex biologics, at sites of disease. This approach offers a platform likely to enhance therapeutic efficacy and decrease off-target side effects. LBPs also can likely be distributed at a relatively low price point, as their production can be economically scaled up. LBPs represent an exciting new means for ensuring healthy lives and promoting well-being for all ages, aligning with the World Health Organization's sustainable development goal 3.

Engineering Microbial Consortia as Living Materials: Advances and Prospectives

The field of Engineered Living Materials (ELMs) integrates engineered living organisms into natural biomaterials to achieve diverse objectives. Multiorganism consortia, prevalent in both naturally occurring and synthetic microbial cultures, exhibit complex functionalities and interrelationships, extending the scope of what can be achieved with individual engineered bacterial strains. However, the ELMs comprising microbial consortia are still in the developmental stage. In this Review, we introduce two strategies for designing ELMs constituted of microbial consortia: a top-down strategy, which involves characterizing microbial interactions and mimicking and reconstructing natural ecosystems, and a bottom-up strategy, which entails the rational design of synthetic consortia and their assembly with material substrates to achieve user-defined functions. Next, we summarize technologies from synthetic biology that facilitate the efficient engineering of microbial consortia for performing tasks more complex than those that can be done with single bacterial strains. Finally, we discuss essential challenges and future perspectives for microbial consortia-based ELMs.

Microbe-material hybrids for therapeutic applications

As natural living substances, microorganisms have emerged as useful resources in medicine for creating microbe-material hybrids ranging from nano to macro dimensions. The engineering of microbe-involved nanomedicine capitalizes on the distinctive physiological attributes of microbes, particularly their intrinsic "living" properties such as hypoxia tendency and oxygen production capabilities. Exploiting these remarkable characteristics in combination with other functional materials or molecules enables synergistic enhancements that hold tremendous promise for improved drug delivery, site-specific therapy, and enhanced monitoring of treatment outcomes, presenting substantial opportunities for amplifying the efficacy of disease treatments. This comprehensive review outlines the microorganisms and microbial derivatives used in biomedicine and their specific advantages for therapeutic application. In addition, we delineate the fundamental strategies and mechanisms employed for constructing microbe-material hybrids. The diverse biomedical applications of the constructed microbe-material hybrids, encompassing bioimaging, anti-tumor, anti-bacteria, anti-inflammation and other diseases therapy are exhaustively illustrated. We also discuss the current challenges and prospects associated with the clinical translation of microbe-material hybrid platforms. Therefore, the unique versatility and potential exhibited by microbe-material hybrids position them as promising candidates for the development of next-generation nanomedicine and biomaterials with unique theranostic properties and functionalities.

Biomedical engineering utilizing living photosynthetic cyanobacteria and microalgae: Current status and future prospects

Cyanobacteria are the only prokaryotes capable of performing oxygenic photosynthesis on Earth. Besides their traditional roles serving as primary producers, cyanobacteria also synthesize abundant secondary metabolites including carotenoids, alkaloids, peptides, which have been reported to possess medicinal potentials. More importantly, the advancement of synthetic biology technology has further expanded their potential biomedical applications especially using living/engineered cyanobacteria, providing promising and attractive strategies for future disease treatments. To improve the understanding and to facilitate future applications, this review aims to discuss the current status and future prospects of cyanobacterial-based biomedical engineering. Firstly, specific properties of cyanobacteria related with biomedical applications like their natural products of bioactive compounds and heavy metal adsorption were concluded. Subsequently, based on these properties of cyanobacteria, we discussed the progress of their applications in various disease models like hypoxia microenvironment alleviation, wound healing, drug delivery, and so on. Finally, the future prospects including further exploration of cyanobacteria secondary metabolites, the integration of bioactive compounds synthesized by cyanobacteria in situ with medical diagnosis and treatment, and the optimization of in vivo application were critically presented. The review will promote the studies related with cyanobacteria-based biomedical engineering and its practical application in clinical trials in the future.

Engineered Cyanobacteria-Based Living Materials for Bioremediation of Heavy Metals Both In Vitro and In Vivo

The pollution caused by heavy metals (HMs) represents a global concern due to their serious environmental threat. Photosynthetic cyanobacteria have a natural niche and the ability to remediate HMs such as cadmium. However, their practical application is hindered by a low tolerance to HMs and issues related to recycling. In response to these challenges, this study focuses on the development and evaluation of engineered cyanobacteria-based living materials for HMs bioremediation. Genes encoding phytochelatins (PCSs) and metallothioneins (MTs) were introduced into the model cyanobacterium Synechocystis sp. PCC 6803, creating PM/6803. The strain exhibited improved tolerance to multiple HMs and effectively removed a combination of Cd2+, Zn2+, and Cu2+. Using Cd2+ as a representative, PM/6803 achieved a bioremediation rate of approximately 21 μg of Cd2+/OD750 under the given test conditions. To facilitate its controllable application, PM/6803 was encapsulated using sodium alginate-based hydrogels (PM/6803@SA) to create "living materials" with different shapes. This system was feasible, biocompatible, and effective for removing Cd2+ under simulated conditions of zebrafish and mice models. Briefly, in vitro application of PM/6803@SA efficiently rescued zebrafish from polluted water containing Cd2+, while in vivo use of PM/6803@SA significantly decreased the Cd2+ content in mice bodies and restored their active behavior. The study offers feasible strategies for HMs bioremediation using the interesting biomaterials of engineered cyanobacteria both in vitro and in vivo.

Plants as a cost-effective source for customizable photosynthetic wound dressings: A proof of concept study

Oxygen is essential for tissue regeneration, playing a crucial role in several processes, including cell metabolism and immune response. Therefore, the delivery of oxygen to wounds is an active field of research, and recent studies have highlighted the potential use of photosynthetic biomaterials as alternative oxygenation approach. However, while plants have traditionally been used to enhance tissue regeneration, their potential to produce and deliver local oxygen to wounds has not yet been explored. Hence, in this work we studied the oxygen-releasing capacity of Marchantia polymorpha explants, showing their capacity to release oxygen under different illumination settings and temperatures. Moreover, co-culture experiments revealed that the presence of these explants had no adverse effects on the viability and morphology of fibroblasts in vitro, nor on the viability of zebrafish larvae in vivo. Furthermore, oxygraphy assays demonstrate that these explants could fulfill the oxygen metabolic requirements of zebrafish larvae and freshly isolated skin biopsies ex vivo. Finally, the biocompatibility of explants was confirmed through a human skin irritation test conducted in healthy volunteers following the ISO-10993-10-2010. This proof-of-concept study provides valuable scientific insights, proposing the potential use of freshly isolated plants as biocompatible low-cost oxygen delivery systems for wound healing and tissue regeneration.

Fighting bacteria with bacteria: A biocompatible living hydrogel patch for combating bacterial infections and promoting wound healing

Bacterial infections are among the most critical global health challenges that seriously threaten the security of human. To address this issue, a biocompatible engineered living hydrogel patch was developed by co-embedding engineered photothermal bacteria (EM), photosensitizer (porphyrin) and reactive oxygen species amplifier (laccase) in a protein hydrogel. Remarkably, the genetice engineered bacteria can express melanin granules in vivo and this allows them to exhibit photothermal response upon being exposed to NIR-II laser (1064 nm) irradiation. Besides, electrostatically adhered tetramethylpyridinium porphyrin (TMPyP) on the bacterial surface and encapsulated laccase (Lac) in protein gel can generate highly toxic singlet oxygen (1O2) and hydroxyl radical (·OH) in the presence of visible light and lignin, respectively. Interestingly, the engineered bacteria hydrogel patch (EMTL@Gel) was successfully applied in synergistic photothermal, photodynamic and chemodynamic therapy, in which it was able to efficiently treat bacterial infection in mouse wounds and enhance wound healing. This work demonstrates the concept of "fighting bacteria with bacteria" combining bacterial engineering and material engineering into an engineered living hydrogel path that can synergistically boost the therapeutic outcome. STATEMENT OF SIGNIFICANCE: Genetically engineered bacteria produce melanin granules in vivo, exhibiting remarkable photothermal properties. These bacteria, along with a photosensitizer (TMPyP) and a reactive oxygen species amplifier (laccase), are incorporated into a biocompatible protein hydrogel patch. Under visible light, the patch generates toxic singlet oxygen (1O2) and hydroxyl radical (·OH), demonstrates outstanding synergistic effects in photothermal, photodynamic, and chemodynamic therapy, effectively treating bacterial infections and promoting wound healing in mice.

Engineering the next generation of theranostic biomaterials with synthetic biology

Biomaterials have evolved from inert materials to responsive entities, playing a crucial role in disease diagnosis, treatment, and modeling. However, their advancement is hindered by limitations in chemical and mechanical approaches. Synthetic biology enabling the genetically reprograming of biological systems offers a new paradigm. It has achieved remarkable progresses in cell reprogramming, engineering designer cells for diverse applications. Synthetic biology also encompasses cell-free systems and rational design of biological molecules. This review focuses on the application of synthetic biology in theranostics, which boost rapid development of advanced biomaterials. We introduce key fundamental concepts of synthetic biology and highlight frontier applications thereof, aiming to explore the intersection of synthetic biology and biomaterials. This integration holds tremendous promise for advancing biomaterial engineering with programable complex functions.

Bacteria-based drug delivery for treating non-oncological diseases

Bacteria inhabit all over the human body, especially the skin, gastrointestinal tract, respiratory tract, urogenital tract, as well as specific lesion sites, such as wound and tumor. By leveraging their distinctive attributes including rapid proliferation, inherent abilities to colonize various biointerfaces in vivo and produce diverse biomolecules, and the flexibility to be functionalized via genetic engineering or surface modification, bacteria have been widely developed as living therapeutic agents, showing promising potential to make a great impact on the exploration of advanced drug delivery systems. In this review, we present an overview of bacteria-based drug delivery and its applications in treating non-oncological diseases. We systematically summarize the physiological positions where living bacterial therapeutic agents can be delivered to, including the skin, gastrointestinal tract, respiratory tract, and female genital tract. We discuss the success of using bacteria-based drug delivery systems in the treatment of diseases that occur in specific locations, such as skin wound healing/infection, inflammatory bowel disease, respiratory diseases, and vaginitis. We also discuss the advantages as well as the limitations of these living therapeutics and bacteria-based drug delivery, highlighting the key points that need to be considered for further translation. This review article may provide unique insights for designing next-generation bacteria-based therapeutics and developing advanced drug delivery systems.

Instant Protection Spray for Anti-Infection and Accelerated Healing of Empyrosis

Distinct from common injuries, deep burns often require a chronic recovery cycle for healing and long-term antibiotic treatment to prevent infection. The rise of drug-resistant bacteria has caused antibiotics to no longer be perfect, and continuous drug use can easily lead to repeated infection and even death. Inspired by wild animals that chew plants to prevent wound infection, probiotic extracts with a structure similar to the tailspike of phage are obtained from Lactobacillus casei and combined with different flavones to design a series of nonantibiotic bactericides. These novel antibacterial agents are combined with a rapid gelation spray with a novel cross-angle layout to form an instant protection spray (IPS) and provide a physical and anti-infectious barrier for burns within 30 s. This IPS is able to sterilize 100.00% and 96.14% of multidrug-resistant Staphylococcus aureus (MRSA) in vitro and in vivo, respectively. In addition, it is found to effectively reduce inflammation in MRSA-infected burns in rats and to promote tissue healing.

Protein/polysaccharide-based hydrogels loaded probiotic-mediated therapeutic systems: A review

The natural characteristics of protein/polysaccharide-based hydrogels, as a potential drug delivery platform, have attracted extensive attention. Probiotics have attracted renewed interest in drug research because of their beneficial effects on host health. The idea of using probiotics loaded on protein/polysaccharide-based hydrogels as potential drugs to treat different diseases has been put forward and shows great prospects. Based on this, in this review, we highlight the design strategy of hydrogels loaded probiotic-mediated therapy systems and review the potential diseases that have been proved to be treatable in the laboratory, including promoting wound healing and improving intestinal health and vaginal health, and discuss the challenges existing in the current design.

Photopolymerizable, immunomodulatory hydrogels of gelatin methacryloyl and carboxymethyl chitosan as all-in-one strategic dressing for wound healing

Microenvironment regeneration in wound tissue is crucial for wound healing. However, achieving desirable wound microenvironment regeneration involves multiple stages, including hemostasis, inflammation, proliferation, and remodeling. Traditional wound dressings face challenges in fully manipulating all these stages to achieve quick and complete wound healing. Herein, we present a VEGF-loaded, versatile wound dressing hydrogel based on gelatin methacryloyl (GelMA) and carboxymethyl chitosan (CMCS), which could be easily fabricated using UV irradiation. The newly designed GelMA-CMCS@VEGF hydrogel not only exhibited strong tissue adhesion capacity due to the interactions between CMCS active groups and biological tissues, but also possessed desirable extensible properties for frequently moving skins and joints. Furthermore, the hydrogel demonstrates exceptional abilities in blood cell coagulation, hemostasis and cell recruitment, leading to the promotion of endothelial cells proliferation, adhesion, migration and angiogenesis. Additionally, in vivo studies demonstrated that the hydrogel drastically shortened hemostatic time, and achieved satisfactory therapeutic efficacy by suppressing inflammation, modulating M1/M2 polarization of macrophages, significantly promoting collagen deposition, stimulating angiogenesis, epithelialization and tissue remodeling. This work contributes to the design of versatile hydrogel dressings for rapid and complete wound healing therapy.

Recent advances in single-cell engineered live biotherapeutic products research for skin repair and disease treatment

The human microbiome has emerged as a key player in maintaining skin health, and dysbiosis has been linked to various skin disorders. Amidst growing concerns regarding the side effects of antibiotic treatments, the potential of live biotherapeutic products (LBPs) in restoring a healthy microbiome has garnered significant attention. This review aims to evaluate the current state of the art of the genetically or metabolically engineered LBPs, termed single-cell engineered LBPs (eLBPs), for skin repair and disease treatment. While some studies demonstrate promising outcomes, the translation of eLBPs into clinical applications remains a significant hurdle. Substantial concerns arise regarding the practical implementation and scalability of eLBPs, despite the evident potential they hold in targeting specific cells and delivering therapeutic agents. This review underscores the need for further research, robust clinical trials, and the exploration of current advances in eLBP-based bioengineered bacterial chassis and new outlooks to substantiate the viability and effectiveness of eLBPs as a transformative approach in skin repair and disease intervention.

Bioinspired mineralization of engineered living materials to promote osteogenic differentiation

In this work, Engineered Living Materials (ELMs), based on the combination of genetically-modified bacteria and mineral-reinforced organic matrices, and endowed with self-healing or regenerative properties and adaptation to specific biological environments were developed. Concretely, we produced ELMs combining human mesenchymal stem cells (hMSCs) and Lactococcus lactis (L. lactis), which was specifically programmed to deliver bone morphogenetic protein (BMP-2) upon external stimulation using nisin, into mineralized alginate matrices. The hybrid organic/inorganic matrix was built through a protocol, inspired by bone mineralization, in which alginate (Alg) assembly and apatite (HA) mineralization occurred simultaneously driven by calcium ions. Chemical composition, structure and reologhical properties of the hybrid 3D matrices were dedicately optimized prior the incorportation of the living entities. Then, the same protocol was reproduced in the presence of hMSC and engineered L. lactis that secrete BMP-2 resulting in 3D hybrid living hydrogels. hMSC viability and osteogenic differentiation in the absence and presence of the bacteria were evaluated by live/dead and quantitative real-time polymerase chain reaction (qPCR) and immunofluorescence assays, respectively. Results demonstrate that these 3D engineered living material support osteogenic differentiation of hMSCs due to the synergistic effect between HA and the growth factors BMP-2 delivered by L. lactis.

Antifungal bio-coating of endotracheal tube built by overexpressing the MCP1 gene of Saccharomyces boulardii and employing hydrogel as a "house" to antagonize Candida albicans

BACKGROUND

For some ICU patients, an artificial airway must be established with an endotracheal tube, but Candida albicans can easily adhere to the tube surface and form a biofilm, leading to potentially life threatening fungal infections. Therefore, it is urgent to prevent and reduce C. albicans infections introduced by the endotracheal tube. However, there are few antifungal drugs effective against C. albicans, and each of these drugs may have adverse effects on human cells. Saccharomyces boulardii is regarded as an alternative strategy to inhibit the adhesion of C. albicans, but it is affected by environmental stress. We hypothesized that it is feasible to strengthen the antagonistic ability of S. boulardii via encapsulating and genetically modification.

METHODS

In this study, a bioactive material carrying the overexpressed MCP1 gene of Saccharomyces boulardii was constructed based on one-step photo-crosslinking. This material achieved spatial growth control of S. boulardii by encapsulating each S. boulardii cell within a hydrogel pore. The bioactive material was coated on an endotracheal tube and tested for its ability to inhibit the adhesion of C. albicans. Additionally, the material's antagonistic activity towards C. albicans was evaluated by detecting intracellular Adenosine-triphosphate content, reactive oxygen species level and the activity of antioxidative enzymes. Tissue invasion experiment was executed to further evaluate the anti-adhesion ability of S. boulardii bio-coating.

RESULTS

Encapsulating the overexpression of MCP1 by S. boulardii in hydrogel pores enhanced the viability of probiotics in the presence of high salt and oxidation stress. When used as the coating of an endotracheal tube, the S. boulardii bioactive material efficiently inhibited the adhesion of C. albicans by impairing the activities of superoxide dismutase and catalase and disturbing mitochondrial functions. In vivo, the S. boulardii bioactive material coating displayed good biocompatibility and reduced the host tissue invasion and virulence of C. albicans.

CONCLUSIONS

The integration of genetic modification and immobilization model breaks the bottleneck of previous application of microorganisms, and provides a new way to prevent fungal infections introduced by endotracheal tubes.

Embedding Living Cells with a Mechanically Reinforced and Functionally Programmable Hydrogel Fiber Platform

Living materials represent a new frontier in functional material design, integrating synthetic biology tools to endow materials with programmable, dynamic, and life-like characteristics. However, a major challenge in creating living materials is balancing the tradeoff between structural stability, mechanical performance, and functional programmability. To address this challenge, a sheath-core living hydrogel fiber platform that synergistically integrates living bacteria with hydrogel fibers to achieve both functional diversity and structural and mechanical robustness is proposed. In the design, microfluidic spinning is used to produce hydrogel fiber, which offers advantages in both structural and functional designability due to their hierarchical porous architectures that can be tailored and their mechanical performance that can be enhanced through a variety of post-processing approaches. By introducing living bacteria, the platform is endowed with programmable functionality and life-like capabilities. This work reconstructs the genetic circuits of living bacteria to express chromoproteins and fluorescent proteins as two prototypes that enable the coloration of living fibers and sensing water pollutants by monitoring the amount of fluorescent protein expressed. Altogether, this study establishes a structure-property-function optimized living hydrogel fiber platform, providing a new tool for accelerating the practical applications of the emerging living material systems.

Organic functional substance engineered living materials for biomedical applications

Modifying living materials with organic functional substances (OFS) is a convenient and effective strategy to control and monitor the transport, engraftment, and secretion processes in living organisms. OFSs, including small organic molecules and organic polymers, own the merit of design flexibility, satisfying performance, and excellent biocompatibility, which allow for living materials functionalization to realize real-time sensing, controlled drug release, enhanced biocompatibility, accurate diagnosis, and precise treatment. In this review, we discuss the different principles of OFS modification on living materials and demonstrate the applications of engineered living materials in health monitoring, drug delivery, wound healing, and tissue regeneration.

Natural biomarocmolecule-based antimicrobial hydrogel for rapid wound healing: A review

Antibacterial hydrogels are a type of hydrogel that is designed to inhibit the growth of bacteria and prevent infections. These hydrogels typically contain antibacterial agents that are either integrated into the polymer network or coated onto the surface of the hydrogel. The antibacterial agents in these hydrogels can work through a variety of mechanisms, such as disrupting bacterial cell walls or inhibiting bacterial enzyme activity. Some examples of antibacterial agents that are commonly used in hydrogels include silver nanoparticles, chitosan, and quaternary ammonium compounds. Antibacterial hydrogels have a wide range of applications, including wound dressings, catheters, and medical implants. They can help to prevent infections, reduce inflammation, and promote tissue healing. In addition, they can be designed with specific properties to suit different applications, such as high mechanical strength or controlled release of antibacterial agents over time. Hydrogel wound dressings have come a long way in recent years, and the future looks very promising for these innovative wound care products. Overall, the future of hydrogel wound dressings is very promising, and we can expect to see continued innovation and advancement in this field in the years to come.