Single cells in nanoshells for the functionalization of living cells

Oral delivery of probiotics using single-cell encapsulation

Adequate intake of live probiotics is beneficial to human health and wellbeing because they can help treat or prevent a variety of health conditions. However, the viability of probiotics is reduced by the harsh environments they experience during passage through the human gastrointestinal tract (GIT). Consequently, the oral delivery of viable probiotics is a significant challenge. Probiotic encapsulation provides a potential solution to this problem. However, the production methods used to create conventional encapsulation technologies often damage probiotics. Moreover, the delivery systems produced often do not have the required physicochemical attributes or robustness for food applications. Single-cell encapsulation is based on forming a protective coating around a single probiotic cell. These coatings may be biofilms or biopolymer layers designed to protect the probiotic from the harsh gastrointestinal environment, enhance their colonization, and introduce additional beneficial functions. This article reviews the factors affecting the oral delivery of probiotics, analyses the shortcomings of existing encapsulation technologies, and highlights the potential advantages of single-cell encapsulation. It also reviews the various approaches available for single-cell encapsulation of probiotics, including their implementation and the characteristics of the delivery systems they produce. In addition, the mechanisms by which single-cell encapsulation can improve the oral bioavailability and health benefits of probiotics are described. Moreover, the benefits, limitations, and safety issues of probiotic single-cell encapsulation technology for applications in food and beverages are analyzed. Finally, future directions and potential challenges to the widespread adoption of single-cell encapsulation of probiotics are highlighted.

External Electrons Directly Stimulate Escherichia coli for Enhancing Biological Hydrogen Production

External electric field has the potential to influence metabolic processes such as biological hydrogen production in microorganisms. Based on this concept, we designed and constructed an electroactive hybrid system for microbial biohydrogen production under an electric field comprised of polydopamine (PDA)-modified Escherichia coli (E. coli) and Ni foam (NF). In this system, electrons generated from NF directly migrate into E. coli cells to promote highly efficient biocatalytic hydrogen production. Compared to that generated in the absence of electric field stimulation, biohydrogen production by the PDA-modified E. coli-based system is significantly enhanced. This investigation has demonstrated the mechanism for electron transfer in a biohybrid system and gives insight into precise basis for the enhancement of hydrogen production by using the multifield coupling technology.

Single-cell coating with biomimetic extracellular nanofiber matrices

Cell therapies offer great promise in the treatment of diseases and tissue regeneration, but their clinical use has many challenges including survival, optimal performance in their intended function, or localization at sites where they are needed for effective outcomes. We report here on a method to coat a biodegradable matrix of biomimetic nanofibers on single cells that could have specific functions ranging from cell signaling to targeting and helping cells survive when used for therapies. The fibers are composed of peptide amphiphile (PA) molecules that self-assemble into supramolecular nanoscale filaments. The PA nanofibers were able to create a mesh-like coating for a wide range of cell lineages with nearly 100 % efficiency, without interrupting the natural cellular phenotype or functions. The targeting abilities of this system were assessed in vitro using human primary regulatory T (hTreg) cells coated with PAs displaying a vascular cell adhesion protein 1 (VCAM-1) targeting motif. This approach provides a biocompatible method for single-cell coating that does not negatively alter cellular phenotype, binding capacity, or immunosuppressive functionality, with potential utility across a broad spectrum of cell therapies. STATEMENT OF SIGNIFICANCE: Cell therapies hold great promise in the treatment of diseases and tissue regeneration, but their clinical use has been limited by cell survival, targeting, and function. We report here a method to coat single cells with a biodegradable matrix of biomimetic nanofibers composed of peptide amphiphile (PA) molecules. The nanofibers were able to coat cells, such as human primary regulatory T cells, with nearly 100 % efficiency, without interrupting the natural cellular phenotype or functions. The approach provides a biocompatible method for single-cell coating that does not negatively alter cellular phenotype, binding capacity, or immunosuppressive functionality, with potential utility across a broad spectrum of cell therapies.

Covalent-organic framework nanobionics for robust cytoprotection

We present a novel study introducing a durable and robust covalent-organic framework (COF) nanocoating, developed in situ on living cells. This COF nanocoating demonstrates remarkable resistance against a diverse range of lethal stressors, including high temperature, extreme pH, ultraviolet radiation, toxic metal ions, organic pollutants, and strong oxidative stress. Notably, the nanocoating exhibits exceptional cell survival enhancement under high temperature and strongly acidic conditions, an aspect yet unexplored in the case of metal-organic framework nanocoatings and other nanomaterials. Moreover, functionalization of the nanocoating with an exogenous enzyme catalase enables yeast fermentation and ethanol production even under strong oxidative stress. Our findings establish the durable and robust COF nanocoating as a reliable platform for safeguarding vulnerable microorganisms to allow their utilisation in a wide range of adverse environments.

Nanoarmor: cytoprotection for single living cells

Single cell modification or hybridization technology has become a popular direction in bioengineering in recent years, with applications in clean energy, environmental stewardship, and sustainable human development. Here, we draw attention to nanoarmor, a representative achievement of cytoprotection and functionalization technology. The fundamental principles of nanoarmor need to be studied with input from multiple disciplines, including biology, chemistry, and material science. In this review, we explain the role of nanoarmor and review progress in its applications. We also discuss three main challenges associated with its development: self-driving ability, heterojunction characteristics, and mineralization formation. Finally, we propose a preliminary classification system for nanoarmor.

A Micrometric Transformer: Compositional Nanoshell Transformation of Fe3+ -Trimesic-Acid Complex with Concomitant Payload Release in Cell-in-Catalytic-Shell Nanobiohybrids

Nanoencapsulation of living cells within artificial shells is a powerful approach for augmenting the inherent capacity of cells and enabling the acquisition of extrinsic functions. However, the current state of the field requires the development of nanoshells that can dynamically sense and adapt to environmental changes by undergoing transformations in form and composition. This paper reports the compositional transformation of an enzyme-embedded nanoshell of Fe3+ -trimesic acid complex to an iron phosphate shell in phosphate-containing media. The cytocompatible transformation allows the nanoshells to release functional molecules without loss of activities and biorecognition, while preserving the initial shell properties, such as cytoprotection. Demonstrations include the lysis and killing of Escherichia coli by lysozyme, and the secretion of interleukin-2 by Jurkat T cells in response to paracrine stimulation by antibodies. This work on micrometric Transformers will benefit the creation of cell-in-shell nanobiohybrids that can interact with their surroundings in active and adaptive ways.

"3-in-1" Hybrid Biocatalysts: Association of Yeast Cells Immobilized in a Sol-Gel Matrix for Determining Sewage Pollution

This study presents a novel ″3-in-1″ hybrid biocatalyst design that combines the individual efficiency of microorganisms while avoiding negative interactions between them. Yeast cells of Ogataea polymorpha VKM Y-2559, Blastobotrys adeninivorans VKM Y-2677, and Debaryomyces hansenii VKM Y-2482 were immobilized in an organosilicon material by using the sol-gel method, resulting in a hybrid biocatalyst. The catalytic activity of the immobilized microorganism mixture was evaluated by employing it as the bioreceptor element of a biosensor. Optical and scanning electron microscopies were used to examine the morphology of the biohybrid material. Elemental distribution analysis confirmed the encapsulation of yeast cells in a matrix composed of methyltriethoxysilane (MTES) and tetraethoxysilane (TEOS) (85 and 15 vol %, respectively). The resulting heterogeneous biocatalyst exhibited excellent performance in determining the biochemical oxygen demand (BOD) index in real surface water samples, with a sensitivity coefficient of 50 ± 3 × 10-3·min-1, a concentration range of 0.3-31 mg/L, long-term stability for 25 days, and a relative standard deviation of 3.8%. These findings demonstrate the potential of the developed hybrid biocatalyst for effective pollution monitoring and wastewater treatment applications.

Whole-cell catalyze L-dopa to dopamine via co-expression of transport protein AroP in Escherichia coli

Dopamine is high-value compound of pharmaceutical interest, but its industrial scale production mostly focuses on chemical synthesis, possessing environment pollution. Bio-manufacturing has caused much attention for its environmental characteristic. Resting cells were employed to as biocatalysts with extraordinary advantages like offering stable surroundings, the inherent presence of expensive cofactors. In this study, whole-cell bioconversion was employed to convert dopa to dopamine. To increase the titer and yield of dopamine production through whole-cell catalysis, three kinds of aromatic amino acid transport protein, AroP, PheP and TyrP, were selected to be co-expressed. The effects of the concentration of L-dopa, pyridoxal-5'- phosphate (PLP), reaction temperature and pH were characterized for improvement of bioconversion. Under optimal conditions, dopamine titer reached 1.44 g/L with molar yield of 46.3%, which is 6.62 times than that of initial conditions. The catalysis productivity of recombinant E. coli co-expressed L-dopa decarboxylase(DDC) and AroP was further enhanced by repeated cell recycling, which maintained over 50% of its initial ability with eight consecutive catalyses. This study was the first to successfully bioconversion of dopamine by whole-cell catalysis. This research provided reference for whole-cell catalysis which is hindered by cell membrane.

An Alternative Thinking in Tumor Therapeutics: Living Yeast Armored with Silicate

A hybrid platform, constructed via the surface "armoring" of living yeasts by a manganese silicate compound (MS@Yeast), is investigated for combinational cancer treatment. The intrinsic characteristics of living yeasts, in both acidophilic and anaerobic conditions, empower the hybrid platform with activated selected colonization in tumors. While silicate particles are delivered in a targeting manner, yeast fermentation occurs at the cancerous region, inducing both alcohol and CO2. The excessive content of alcohol causes the hemangiectasis of tumor tissue, facilitating the penetration of therapeutics into central tumors and subsequent endocytosis. The catalytic Mn2+ ions, released from silicate particles, react with CO2 to induce forceful oxidative stress in tumor cells, ablating the primary tumors. More interestingly, the debris of sacrificed tumor cells and yeasts triggers considerable antitumor immune responses, rejecting both rechallenged and metastatic tumors. The integration of biologically active microorganisms and functional materials, illustrated in this study, provides distinctive perspectives in the exploration of potential therapeutics for tackling cancer.

Chitosan-Based Biomaterials: Insights into Chemistry, Properties, Devices, and Their Biomedical Applications

Chitosan is a marine-origin polysaccharide obtained from the deacetylation of chitin, the main component of crustaceans’ exoskeleton, and the second most abundant in nature. Although this biopolymer has received limited attention for several decades right after its discovery, since the new millennium chitosan has emerged owing to its physicochemical, structural and biological properties, multifunctionalities and applications in several sectors. This review aims at providing an overview of chitosan properties, chemical functionalization, and the innovative biomaterials obtained thereof. Firstly, the chemical functionalization of chitosan backbone in the amino and hydroxyl groups will be addressed. Then, the review will focus on the bottom-up strategies to process a wide array of chitosan-based biomaterials. In particular, the preparation of chitosan-based hydrogels, organic–inorganic hybrids, layer-by-layer assemblies, (bio)inks and their use in the biomedical field will be covered aiming to elucidate and inspire the community to keep on exploring the unique features and properties imparted by chitosan to develop advanced biomedical devices. Given the wide body of literature that has appeared in past years, this review is far from being exhaustive. Selected works in the last 10 years will be considered.

A Semiconductor Biohybrid System for Photo-Synergetic Enhancement of Biological Hydrogen Production

CdS nanoparticles were introduced on E. coli cells to construct a hydrogen generating biohybrid system via the biointerface of tannic acid-Fe complex. This hybrid system promotes good biological activity in a high salinity environment. Under light illumination, the as-synthesized biohybrid system achieves a 32.44 % enhancement of hydrogen production in seawater through a synergistic effect.

Nanoarchitectonics to entrap living cells in silica-based systems: encapsulations with yolk-shell and sepiolite nanomaterials

In the present work, the bottom-up fabrication of biohybrid materials using a nanoarchitectonics approach has been applied to entrap living cells. Unicellular microorganisms, that is, cyanobacteria and yeast cells, have been immobilized in silica and silicate-based substrates organized as nanostructured materials. In a first attempt, matrices based on bionanocomposites of chitosan and alginate incorporating sepiolite clay mineral and shaped as films, beads, or foams have been explored for the immobilization of cyanobacteria. It has been observed that this type of biohybrid substrates leads to serious problems regarding the long-time survival of the encapsulated microorganisms. Alternative procedures using silica-based matrices with low sodium content, generated by sol-gel methods, as well as pre-synthesised yolk-shell bionanohybrids have been studied subsequently. Optical microscopy and SEM confirm that the silica shell microstructures provide a reduced contact between cells. The inorganic matrix increases the survival of the cells and maintains their bioactivity. Thus, the encapsulation efficiency is improved compared to the approach using a direct contact of cells in a silica matrix. Encapsulated yeast produced ethanol over a period of several days, pointing out the useful biocatalytic potential of the approach and suggesting further optimization of the present protocols.

Helicobacter Pylori: A Review of Current Treatment Options in Clinical Practice

BACKGROUND

When prescribing antibiotics, infection eradication rates, local resistance rates, and cost should be among the most essential considerations. Helicobacter pylori is among the most common infections worldwide, and it can lead to burdensome sequela for the patient and the healthcare system, without appropriate treatment. Due to constantly fluctuating resistance rates, regimens must be constantly assessed to ensure effectiveness.

METHODS

This was a narrative review. The sources for this review are as follows: searching on PubMed, Google Scholar, Medline, and ScienceDirect; using keywords: Helicobacter pylori, Treatment Options, Clinical Practice.

RESULTS

Multiple antibiotics are prescribed as part of the regimen to thwart high resistance rates. This can lead to unwanted adverse reactions and adherence issues, due to the amount and timing of medication administration, which also may contribute to resistance. Single-capsule combination capsules have reached the market to ease this concern, but brand-only may be problematic for patient affordability. Due to the previously mentioned factors, effectiveness and affordability must be equally considered.

CONCLUSIONS

This review will utilize guidelines to discuss current treatment options and give cost considerations to elicit the most effective regimen for the patient.

Stretchable Liquid Metal-Based Metal-Polymer Conductors for Fully Screen-Printed Biofuel Cells

We reported a straightforward and low-cost method to fabricate stretchable biofuel cells by using liquid metal-based metal-polymer conductors. The liquid-metal-based metal-polymer conductors had a conductivity of 2.7 × 10⁵ S/m and a stretchability larger than 200%, giving the biofuel cell good conformability to the skin. The glucose biofuel cells (BFCs) yielded a maximum power density as 14.11 μW/cm² at 0.31 V with 0.2 mM glucose, while the lactate BFCs reached 31.00 μW/cm² at 0.51 V with 15 mM lactate. The results of 24 h short circuit current density showed that, with enough biofuel, this patch could be used over the course of an entire day for wearable sensors.

Helicobacter Pylori-Induced Gastric Infections: From Pathogenesis to Novel Therapeutic Approaches Using Silver Nanoparticles

Helicobacter pylori is the first formally recognized bacterial carcinogen and the most important single digestive pathogen responsible for the induction of gastroduodenal diseases such as gastritis, peptic ulcer, and, finally, gastric neoplasia. The recently reported high rates of antimicrobial drug resistance hamper the current therapies of H. pylori, with therapeutic failure reaching up to 40% of patients. In this context, new treatment options and strategies are urgently needed, but the successful development of these new therapeutic tools is conditioned by the understanding of the high adaptability of H. pylori to the gastric acidic environment and the complex pathogenic mechanism. Due to several advantages, including good antibacterial efficiency, possible targeted delivery, and long tissular persistence, silver nanoparticles (AgNPs) offer the opportunity of exploring new strategies to improve the H. pylori therapy. A new paradigm in the therapy of H. pylori gastric infections using AgNPs has the potential to overcome the current medical limitations imposed by the H. pylori drug resistance, which is reported for most of the current organic antibiotics employed in the classical therapies. This manuscript provides an extensive overview of the pathology of H. pylori-induced gastritis, gastric cancer, and extradigestive diseases and highlights the possible benefits and limitations of employing AgNPs in the therapeutic strategies against H. pylori infections.

Alginate@polydopamine@SiO2 microcapsules with controlled porosity for whole-cell based enantioselective biosynthesis of (S)-1-phenylethanol

Whole-cell biocatalysis, owing to its high enantioselectivity, environment friendly and mild reaction condition, show a great prospect in chemical, pharmaceutical and fuel industry. However, several problems still limit its wide applications, mainly concerning the low productivity and poor stability. Although the biocatalyst encapsulated in the most-commonly-used alginate hydrogels demonstrate enhanced stability, it still suffers from low biocatalytic productivity, long-term reusability and poor mass diffusion control. In this work, hybrid alginate@polydopamine@SiO₂ microcapsules with controlled porosity are designed to encapsulate yeast cells for the asymmetric biosynthesis of (S)- 1-phenylethonal from acetophenone. The hybrid microcapsules are formed by the ionic cross-linking of alginate, the polymerization of dopamine monomers and the protamine-assisted colloidal packing of uniform-sized silica nanoparticles. Alginate provides the encapsulated cells with highly biocompatible environment. Polydopamine enables to stimulate the biocatalytic productivity of the encapsulated yeast cells. Silica shells can not only regulate the mass diffusion in biocatalysis but also enhance the long-term mechanical and chemical stability of the microcapsules. The morphology, structure, chemical composition, stability and molecular accessibility of the hybrid microcapsules are investigated in detail. The viability and asymmetric bioreduction performance of the cells encapsulated in microcapsules are evaluated. The 24 h product yield of the cells encapsulated in the hybrid microcapsules shows 1.75 times higher than that of the cells encapsulated in pure alginate microcapsules. After 6 batches, the 24 h product yield of the cells encapsulated in the hybrid microcapsules is well maintained and 2 times higher than that of the cells encapsulated in pure alginate microcapsules. Therefore, the hybrid microcapsules designed in this study enable to enhance the asymmetric biocatalytic activity, stability and reusability of the encapsulated cells, thus contributing to a significant progress in cell-encapsulating materials to be applied in biocatalytic asymmetric synthesis industry.

Activation of a passive, mesoporous silica nanoparticle layer through attachment of bacterially-derived carbon-quantum-dots for protection and functional enhancement of probiotics

Probiotic bacteria employed for food supplementation or probiotic-assisted antibiotic treatment suffer from passage through the acidic gastro-intestinal tract and unintended killing by antibiotics. Carbon-quantum-dots (CQDs) derived from bacteria can inherit different chemical groups and associated functionalities from their source bacteria. In order to yield simultaneous, passive protection and enhanced, active functionality, we attached CQDs pyrolytically carbonized at 220 ​°C from Lactobacillus acidophilus or Escherichia coli to a probiotic strain (Bifidobacterium infantis) using boron hydroxyl-modified, mesoporous silica nanoparticles as an intermediate encapsulating layer. Fourier-transform-infrared-spectroscopy, X-ray-photoelectron-spectroscopy and scanning-electron-microscopy were employed to demonstrate successful encapsulation of B. infantis by silica nanoparticles and subsequent attachment of bacterially-derived CQDs. Thus encapsulated B. infantis possessed a negative surface charge and survived exposure to simulated gastric fluid and antibiotics better than unencapsulated B. infantis. During B. infantis assisted antibiotic treatment of intestinal epithelial layers colonized by E. coli, encapsulated B. infantis adhered and survived in higher numbers on epithelial layers than B. infantis without encapsulation or encapsulated with only silica nanoparticles. Moreover, higher E. coli killing due to increased reactive-oxygen-species generation was observed. In conclusion, the active, protective encapsulation described enhanced the probiotic functionality of B. infantis, which might be considered as a first step towards a fully engineered, probiotic nanoparticle.

Emerging Albumin-Binding Anticancer Drugs for Tumor-Targeted Drug Delivery: Current Understandings and Clinical Translation

Albumin has shown remarkable promise as a natural drug carrier by improving pharmacokinetic (PK) profiles of anticancer drugs for tumor-targeted delivery. The exogenous or endogenous albumin enhances the circulatory half-lives of anticancer drugs and passively target the tumors by the enhanced permeability and retention (EPR) effect. Thus, the albumin-based drug delivery leads to a potent antitumor efficacy in various preclinical models, and several candidates have been evaluated clinically. The most successful example is Abraxane, an exogenous human serum albumin (HSA)-bound paclitaxel formulation approved by the FDA and used to treat locally advanced or metastatic tumors. However, additional clinical translation of exogenous albumin formulations has not been approved to date because of their unexpectedly low delivery efficiency, which can increase the risk of systemic toxicity. To overcome these limitations, several prodrugs binding endogenous albumin covalently have been investigated owing to distinct advantages for a safe and more effective drug delivery. In this review, we give account of the different albumin-based drug delivery systems, from laboratory investigations to clinical applications, and their potential challenges, and the outlook for clinical translation is discussed. In addition, recent advances and progress of albumin-binding drugs to move more closely to the clinical settings are outlined.

ZnO Nanocomposites of Juniperus procera and Dodonaea viscosa Extracts as Antiproliferative and Antimicrobial Agents

Cancer and microbial infections constitute a major burden and leading cause of death globally. The development of therapeutic compounds from natural products is considered a cornerstone in drug discovery. Therefore, in the present study, the ethanolic extract and the fractions of Dodonaea viscosa and Juniperus procera were evaluated for anticancer and antimicrobial activities. It was found that two fractions, JM and DC, exhibited promising anticancer and antimicrobial activities. The JM and DC fractions were further modified into ZnO nanocomposites, which were characterized by SEM, XRD, TGA, and EDX. It was noted that the synthesized nanocomposites displayed remarkable enhancement in cytotoxicity as well as antibacterial activity. Nanocomposite DC–ZnO NRs exhibited cytotoxicity with IC₅₀ values of 16.4 ± 4 (HepG2) and 29.07 ± 2.7 μg/mL (HCT-116) and JM–ZnO NRs with IC₅₀ values of 12.2 ± 10.27 (HepG2) and 24.1 ± 3.0 μg/mL (HCT-116). In addition, nanocomposites of DC (i.e., DC–ZnO NRs) and JM (i.e., JM–ZnO NRs) displayed excellent antimicrobial activity against Staphylococcus aureus with MICs of 2.5 and 1.25 μg/mL, respectively. Moreover, these fractions and nanocomposites were tested for cytotoxicity against normal fibroblasts and were found to be non-toxic. GC-MS analysis of the active fractions were also carried out to discover the possible phytochemicals that are responsible for these activities.

In situ silver nanoparticle coating of virions for quantification at single virus level

In situ labelling and encapsulation of biological entities, such as of single viruses, may provide a versatile approach to modulate their functionality and facilitate their detection at single particle level. Here, we introduce a novel virus metallization approach based on in situ coating of viruses in solution with silver nanoparticles (AgNP) in a two-step synthetic process, i.e. surface activation with a tannic acid - Sn(II) coordination complex, which subsequently induces silver ion (I) reduction. The metalic coating on the virus surface opens the opportunity for electrochemical quantification of the AgNP-tagged viruses by nano-impact electrochemistry on a microelectrode with single particle sensitivity, i.e. enable the detection of particles oherwise undetectable. We show that the silver coating of the virus particles impacting the electrode can be oxidized to produce distinct current peaks the frequency of which show a linear correlation with the virus count. The proof of the concept was done with inactivated Influenza A (H3N2) viruses resulting in their quantitation down to the femtomolar concentrations (ca. 5 × 10⁷ particles per mL) using 50 s counting sequences.

Multiplexing Nanodrug Ameliorates Liver Fibrosis via ROS Elimination and Inflammation Suppression

Liver fibrosis is the leading risk factor for hepatocellular carcinoma. Both oxidative stress and inflammation promote the progression of liver fibrosis, but existing therapeutic strategies tend to focus solely on one issue. Additionally, targeting of pathological microstructures is often neglected. Herein, an esterase-responsive carbon quantum dot-dexamethasone (CD-Dex) is developed for liver fibrosis therapy to simultaneously target pathological microstructures, scavenge reactive oxygen species (ROS), and suppress inflammation. Hepatocyte-targeting CD-Dex can efficiently eliminate the intrahepatic ROS, thereby inhibiting the activation of Kupffer cells, preventing further inflammation progression. Moreover, released dexamethasone (Dex) also suppresses inflammatory response by inhibiting the infiltration of inflammatory cells. Antifibrotic experiments demonstrate that CD-Dex significantly alleviates liver injury and collagen deposition, consequently preventing the progression of liver fibrosis. Taken together, these findings suggest that via ROS elimination and inflammation suppression, the newly developed multiplexing nanodrug exhibits great potential in liver fibrosis therapy.

Unveiling the Surface and the Ultrastructure of Palladized Fungal Biotemplates

In this paper, two biosystems based on filamentous fungi and Pd nanoparticles (NPs) were synthesized and structurally characterized. In the first case, results concerning the integration and distribution of Pd-NPs on Phialomyces macrosporus revealed that nanoparticles are accumulated on the cell wall, keeping the cytoplasm isolated from abiotic particles. However, the Penicillium sp. species showed an unexpected internalization of Pd-NPs in the fungal cytosol, becoming a promising biosystem to further studies of in vivo catalytic reactions. Next, we report a new solution-based strategy to prepare palladized biohybrids through sequential reduction of Pd²⁺ ions over previously harvested fungus/Au-NP composites. The chemical composition and the morphology of the biohybrid surface were characterized using a combination of scanning electron microscopy, transmission electron microscopy, and photoelectron spectroscopy. The deposition of Pd⁰ over the fungal surface produced biohybrids with a combination of Au and Pd in the NPs. Interestingly, other chemical species such as Au⁺ and Pd²⁺ are also observed on the outermost wall of microorganisms. Finally, the application of A. niger/AuPd-NP biohybrids in the 3-methyl-2-buten-1-ol hydrogenation reaction is presented for the first time. Biohybrids with a high fraction of Pd⁰ are active for this catalytic reaction.

Decorating Bacteria with a Therapeutic Nanocoating for Synergistically Enhanced Biotherapy

Disorders in the gut microbiota have been implicated in various diseases, such as inflammatory bowel diseases, diabetes, and cancers. Oral microecologics are of great importance due to their ability to directly intervene the gut microbiome as well as their noninvasiveness and low side effects, while have suffered from low bioavailability and a single therapeutic effect. Here, probiotics are coated with a therapeutic nanocoating for synergistically enhanced biotherapy, a method inspired by the robust protective and therapeutic effectiveness of silkworm cocoon. With its transition from a random coil to β-sheet conformation, silk fibroin can self-assemble onto the surface of bacteria. By a simple layer-by-layer procedure, an entire nanocoating can be formed along with a near quantitative coating ratio and almost uninfluenced bacterial viability. Thanks to its protective barrier role and innate pharmaceutical activity, silk fibroin nanocoating endows the coated bacteria with a markedly improved survival against gastric insults and a synergistically enhanced therapeutic effect in a murine model of intestinal mucositis. This work demonstrates how therapeutic elements can be combined with probiotics via a simple coating strategy and proposes an alternative to enhance bioavailability and treatment efficacy of oral microecologics.

Alginate@TiO2 hybrid microcapsules with high in vivo biocompatibility and stability for cell therapy

Designing new materials to encapsulate living therapeutic cells for the treatment of the diseases caused by protein or hormone deficiencies is a great challenge. The desired materials need to be biocompatible towards both entrapped cells and host organisms, have long-term in vivo stability after implantation, allow the diffusion of nutrients and metabolites, and ensure perfect immune-isolation. The current work investigates the in vivo biocompatibility and stability of alginate@TiO₂ hybrid microcapsules and the immune-isolation of entrapped HepG2 cells, to assess their potential for cell therapy. A comparison was made with alginate-silica hybrid microcapsules (ASA). These two hybrid microcapsules are implanted subcutaneously in female Wistar rats. The inflammatory responses of the rats are monitored by the histological examination of the implants and the surrounding tissues, to indicate their in vivo biocompatibility towards the hosts. The in vivo stability of the microcapsules is evaluated by the recovery rate of the intact microcapsules after implantation. The immune-isolation of the entrapped cells is assessed by their morphology, membrane integrity and intracellular enzymatic activity. The results show high viability of the entrapped cells and insignificant inflammation of the hosts, suggesting the excellent biocompatibility of alginate@TiO₂ and ASA microcapsules towards both host organisms and entrapped cells. Compared to the ASA microcapsules, more intact alginate@TiO₂ hybrid microcapsules are recovered 2-day and 2-month post-implantation and more cells remain alive, proving their better in vivo biocompability, stability, and immune-isolation. The present study demonstrates that the alginate@TiO₂ hybrid microcapsule is a highly promising implantation material for cell therapy.

Bioinspired Cell Silicification: From Extracellular to Intracellular

In nature, biosilicification directs the formation of elaborate amorphous silica exoskeletons that provide diatoms mechanically strong, chemically inert, non-decomposable silica armor conferring chemical and thermal stability as well as resistance to microbial attack, without changing the optical transparency or adversely effecting nutrient and waste exchange required for growth. These extraordinary silica/cell biocomposites have inspired decades of biomimetic research aimed at replication of diatoms' hierarchically organized exoskeletons, immobilization of cells or living organisms within silica matrices and coatings to protect them against harmful external stresses, genetic re-programming of cellular functions by virtue of physico-chemical confinement within silica, cellular integration into devices, and endowment of cells with non-native, abiotic properties through facile silica functionalization. In this Perspective, we focus our discussions on the development and concomitant challenges of bioinspired cell silicification ranging from "cells encapsulated within 3D silica matrices" and "cells encapsulated within 2D silica shells" to extra- and intracellular silica replication, wherein all biomolecular interfaces are encased within nanoscopic layers of amorphous silica. We highlight notable examples of advances in the science and technology of biosilicification and consider challenges to advancing the field, where we propose cellular "mineralization" with arbitrary nanoparticle exoskeletons as a generalizable means to impart limitless abiotic properties and functions to cells, and, based on the interchangeability of water and silicic acid and analogies between amorphous ice and amorphous silica, we consider "freezing" cells within amorphous silica as an alternative to cryo-preservation.

Single-cell yolk-shell nanoencapsulation for long-term viability with size-dependent permeability and molecular recognition

Like nanomaterials, bacteria have been unknowingly used for centuries. They hold significant economic potential for fuel and medicinal compound production. Their full exploitation, however, is impeded by low biological activity and stability in industrial reactors. Though cellular encapsulation addresses these limitations, cell survival is usually compromised due to shell-to-cell contacts and low permeability. Here, we report ordered packing of silica nanocolloids with organized, uniform and tunable nanoporosities for single cyanobacterium nanoencapsulation using protamine as an electrostatic template. A space between the capsule shell and the cell is created by controlled internalization of protamine, resulting in a highly ordered porous shell-void-cell structure formation. These unique yolk-shell nanostructures provide long-term cell viability with superior photosynthetic activities and resistance in harsh environments. In addition, engineering the colloidal packing allows tunable shell-pore diameter for size-dependent permeability and introduction of new functionalities for specific molecular recognition. Our strategy could significantly enhance the activity and stability of cyanobacteria for various nanobiotechnological applications.

Engineering High-Yield Biopolymer Secretion Creates an Extracellular Protein Matrix for Living Materials

The bacterial extracellular matrix forms autonomously, giving rise to complex material properties and multicellular behaviors. Synthetic matrix analogues can replicate these functions but require exogenously added material or have limited programmability. Here, we design a two-strain bacterial system that self-synthesizes and structures a synthetic extracellular matrix of proteins. We engineered Caulobacter crescentus to secrete an extracellular matrix protein composed of an elastin-like polypeptide (ELP) hydrogel fused to supercharged SpyCatcher [SC^(-)]. This biopolymer was secreted at levels of 60 mg/liter, an unprecedented level of biomaterial secretion by a native type I secretion apparatus. The ELP domain was swapped with either a cross-linkable variant of ELP or a resilin-like polypeptide, demonstrating this system is flexible. The SC^(-)-ELP matrix protein bound specifically and covalently to the cell surface of a C. crescentus strain that displays a high-density array of SpyTag (ST) peptides via its engineered surface layer. Our work develops protein design guidelines for type I secretion in C. crescentus and demonstrates the autonomous secretion and assembly of programmable extracellular protein matrices, offering a path forward toward the formation of cohesive engineered living materials.IMPORTANCE Engineered living materials (ELM) aim to mimic characteristics of natural occurring systems, bringing the benefits of self-healing, synthesis, autonomous assembly, and responsiveness to traditional materials. Previous research has shown the potential of replicating the bacterial extracellular matrix (ECM) to mimic biofilms. However, these efforts require energy-intensive processing or have limited tunability. We propose a bacterially synthesized system that manipulates the protein content of the ECM, allowing for programmable interactions and autonomous material formation. To achieve this, we engineered a two-strain system to secrete a synthetic extracellular protein matrix (sEPM). This work is a step toward understanding the necessary parameters to engineering living cells to autonomously construct ELMs.

Construction of bifunctional living red blood cells for combined photothermal-chemotherapy

Modifying living cells using in-situ synthesized nanomaterials to endow them with new functions is highly desirable. Herein we report intra- and extra-cellular dual-modified red blood cells (RBCs) with intracellular CaCO₃ nanoparticles (NPs) and extracellular polypyrrole-folic acid (PPy-FA) coating, which are exploited as a bifunctional drug carrier. The functionalized living cells (CaCO₃@RBC@PPy-FA) are fabricated through first the intracellular in situ reaction of exogenous Ca²⁺ and CO₃^2- ions to generate CaCO₃ NPs, then polymerization of pyrrole and finally modification of folic acid (FA) on the membrane of individual cells, forming a CaCO₃@RBC@PPy-FA structure. As a result, such dual-modified RBCs not only preserve the original performances of the cells but also possess the desirable properties as a drug carrier, such as high loading capacity due to the action of CaCO₃ NPs, targeting and light-controlled drug release due to the action of PPy-FA. Under NIR laser stimulation, these bifunctional RBCs (DOX-CaCO₃@RBC@PPy-FA) present an instant release profile of doxorubicin (DOX) and have high targeting-ability toward cancer cells, achieving a marked synergistic combined photothermal-chemotherapy effect.

Layer-by-layer assembly of Au and CdS nanoparticles on the surface of bacterial cells for photo-assisted bioanodes in microbial fuel cells

Surface modification of exoelectrogens with photoelectric materials is a promising way for achieving photo-assisted microbial fuel cells (MFCs). However, the poor conductivity of most photoelectric materials inevitably hampers the electron transfer inside bacterial biofilms. Herein, by utilizing the electrostatic layer-by-layer assembly strategy, the conductive Au nanoparticles (NPs) and photo-responsive CdS NPs were alternatively modified onto the surface of Escherichia coli for photo-assisted bioanodes in MFCs. The CdS layer was found to protect the bacterial cells from light illumination-induced inactivation. When the CdS layer coexisted with an outer layer of Au NPs, the modification of the CdS layers can generate photocurrent without any loss of biocurrent, because the outer Au layer could serve as a conductive channel for the photoelectron and bioelectron transfer between each bacterium. But the increase of CdS layers failed to further improve the photocurrent, implying that the light was inaccessible to the inner CdS layer. This work brings a universal way to fabricate conductive and photo-responsive bacteria, which would deepen the application of cell-surface modification technology in photo-assisted MFCs.

Improvement of organisms by biomimetic mineralization: A material incorporation strategy for biological modification

Biomineralization, a bio-organism controlled mineral formation process, plays an important role in linking biological organisms and mineral materials in nature. Inspired by biomineralization, biomimetic mineralization is used as a bridge tool to integrate biological organisms and functional materials together, which can be beneficial for the development of diversified functional organism-material hybrids. In this review, recent progresses on the techniques of biomimetic mineralization for organism-material combinations are summarized and discussed. Based upon these techniques, the preparations and applications of virus-, prokaryotes-, and eukaryotes-material hybrids have been presented and they demonstrate the great potentials in the fields of vaccine improvement, cell protection, energy production, environmental and biomedical treatments, etc. We suggest that more researches about functional organism and material combination with more biocompatible techniques should be developed to improve the design and applications of specific organism-material hybrids. These rationally designed organism-material hybrids will shed light on the production of "live materials" with more advanced functions in future. STATEMENT OF SIGNIFICANCE: This review summaries the recent attempts on improving biological organisms by their integrations with functional materials, which can be achieved by biomimetic mineralization as the combination tool. The integrated materials, as the artificial shells or organelles, confer diversified functions on the enclosed organisms. The successful constructions of various virus-, prokaryotes-, and eukaryotes-material hybrids have demonstrated the great potentials of the material incorporation strategy in vaccine development, cancer treatment, biological photosynthesis and environment protection etc. The suggested challenges and perspectives indicate more inspirations for the future development of organism-material hybrids.

Bioinspired cell-in-shell systems in biomedical engineering and beyond: Comparative overview and prospects

With the development in tissue engineering, cell transplantation, and genetic technologies, living cells have become an important therapeutic tool in clinical medical care. For various cell-based technologies including cell therapy and cell-based sensors in addition to fundamental studies on single-cell biology, the cytoprotection of individual living cells is a prerequisite to extend cell storage life or deliver cells from one place to another, resisting various external stresses. Nature has evolved a biological defense mechanism to preserve their species under unfavorable conditions by forming a hard and protective armor. Particularly, plant seeds covered with seed coat turn into a dormant state against stressful environments, due to mechanical and water/gas constraints imposed by hard seed coat. However, when the environmental conditions become hospitable to seeds, seed coat is ruptured, initiating seed germination. This seed dormancy and germination mechanism has inspired various approaches that artificially induce cell sporulation via chemically encapsulating individual living cells within a thin but tough shell forming a 3D "cell-in-shell" structure. Herein, the recent advance of cell encapsulation strategies along with the potential advantages of the 3D "cell-in-shell" system is reviewed. Diverse coating materials including polymeric shells and hybrid shells on different types of cells ranging from microbes to mammalian cells will be discussed in terms of enhanced cytoprotective ability, control of division, chemical functionalization, and on-demand shell degradation. Finally, current and potential applications of "cell-in-shell" systems for cell-based technologies with remaining challenges will be explored.

Biodegradable nanofibrous temperature-responsive gelling microspheres for heart regeneration

Myocardial infarction (heart attack) is the number one killer of heart patients. Existing treatments for heart attack do not address the underlying problem of cardiomyocyte (CM) loss and cannot regenerate the myocardium. Introducing exogenous cardiac cells is required for heart regeneration due to the lack of resident progenitor cells and very limited proliferative potential of adult CMs. Poor retention of transplanted cells is the critical bottleneck of heart regeneration. Here, we report the invention of a poly(l-lactic acid)-b-poly(ethylene glycol)-b-poly(N-Isopropylacrylamide) copolymer and its self-assembly into nanofibrous gelling microspheres (NF-GMS). The NF-GMS undergo thermally responsive transition to form not only a 3D hydrogel after injection in vivo, but also exhibit architectural and structural characteristics mimicking the native extracellular matrix (ECM) of nanofibrous proteins and gelling proteoglycans or polysaccharides. By integrating the ECM-mimicking features, injectable form, and the capability of maintaining 3D geometry after injection, the transplantation of hESC-derived CMs carried by NF-GMS led to a striking 10-fold graft size increase over direct CM injection in an infarcted rat model, which is the highest reported engraftment to date. Furthermore, NF-GMS carried CM transplantation dramatically reduced infarct size, enhanced integration of transplanted CMs, stimulated vascularization in the infarct zone, and led to a substantial recovery of cardiac function. The NF-GMS may also serve as advanced injectable and integrative biomaterials for cell/biomolecule delivery in a variety of biomedical applications.

Nanobiohybrids: Materials approaches for bioaugmentation

Nanobiohybrids, synthesized by integrating functional nanomaterials with living systems, have emerged as an exciting branch of research at the interface of materials engineering and biological science. Nanobiohybrids use synthetic nanomaterials to impart organisms with emergent properties outside their scope of evolution. Consequently, they endow new or augmented properties that are either innate or exogenous, such as enhanced tolerance against stress, programmed metabolism and proliferation, artificial photosynthesis, or conductivity. Advances in new materials design and processing technologies made it possible to tailor the physicochemical properties of the nanomaterials coupled with the biological systems. To date, many different types of nanomaterials have been integrated with various biological systems from simple biomolecules to complex multicellular organisms. Here, we provide a critical overview of recent developments of nanobiohybrids that enable new or augmented biological functions that show promise in high-tech applications across many disciplines, including energy harvesting, biocatalysis, biosensing, medicine, and robotics.

Comparison of different zinc precursors for the construction of zeolitic imidazolate framework-8 artificial shells on living cells

The robust cell-in-shell structure is highly desirable for endowing living cells with an artificial exoskeleton to defend them from many environmental factors such as osmotic pressure, shear force, heat, UV radiation, and enzymes. Cell encapsulation has shown potential applications in many fields and attracted increasing interest. However, the influences of the precursors on the cell viability during the shell formation process are not clear and seldom investigated. Here, zinc nitrite, zinc acetate and zinc sulfate were applied individually to synthesize zeolitic imidazolate framework-8 (ZIF-8) shells on living cells. All the zinc salt precursors could convert to a ZIF-8 layer on the living cell surface. The zinc salts and organic ligand did not exhibit obvious toxicity to yeast cells when applied individually. However, dead cells were observed during the living cell encapsulation process using different zinc precursors. Compared with zinc nitrate and zinc acetate, ZIF-8 formed by zinc sulfate led to a higher percentage of cell death, especially under high concentrations of zinc sulfate. Cell division was suppressed by the ZIF-8 shell but restored fully upon shell removal by EDTA solution or pH 4.0 buffer. Escherichia coli (E. coli) cells showed a lower percentage of cell death, indicating excellent tolerance to the ZIF-8 encapsulation process. This work illustrates the cell toxicity during the formation of ZIF-8 cell shells by different zinc salts and engineering of the cell growth by MOF coating, which could provide a foundation for further quantitative analysis and potential applications in biomedicine and bioengineering.

Solar activation of fungus coated in photothermal cloth

Described herein is a novel bioorthogonal method for microorganism (Aspergillus oryzae) modification which coats the microorganism with a photothermal conversion cloth for staying bioactive in cold environments.

Living whole-cell catalysis in compartmentalized emulsion

Whole-cell biocatalysis plays an important role in biotransformation with unique features such as good tolerance of solvents and easy recycling. However, the relatively low catalytic efficiency limits their use in real production. In this study, a multi-compartmentalized emulsion in organic solvent was constructed to encapsulate living cells for enhanced catalytic performance. Extraordinary large interfacial area of the emulsion improved the bioactivity of Escherichia coli (E. Coli) cells up to 137 times compared to a standard biphasic system. The emulsion was stabilized by a biocompatible polymer and prepared by gentle shaking by hand, which resulted in good cell viability. Moreover, the encapsulated cells could be easily recycled, and the activity remained more than 70% after five cycles. This work provides a promising approach for utilizing whole-cell catalysts for efficient organic catalysis.

Click Reaction for Reversible Encapsulation of Single Yeast Cells

Cell surface engineering is an emerging technology to encapsulate cells in order to enhance their functions. However, methods for reversible encapsulation of cells with abiotic functionalities are rare. Herein, we describe a phenylboronic acid based click reaction for encapsulation of single yeast cells using mesoporous silica nanoparticles (MSNs). This encapsulation does not impact natural growth of the cells and leads to a significant enhancement of cell survival in a variety of hostile environments. Owing to the glucose-responsiveness of the boronate ester bond between cell surface polysaccharides and B(OH)₂-grafted MSNs, encapsulation was reversible by addition or removal of glucose. This effort offers living cells effective protection under harsh conditions and enables reversible assembling-detaching of abiotic functions.

An overview on enrichment methods for cell surface proteome profiling

Cell surface proteins are essential for many important biological processes, including cell-cell interactions, signal transduction, and molecular transportation. With the characteristics of low abundance, high hydrophobicity, and high heterogeneity, it is difficult to get a comprehensive view of cell surface proteome by direct analysis. Thus, it is important to selectively enrich the cell surface proteins before liquid chromatography with mass spectrometry analysis. In recent years, a variety of enrichment methods have been developed. Based on the separation mechanism, these methods could be mainly classified into three types. The first type is based on their difference in the physicochemical property, such as size, density, charge, and hydrophobicity. The second one is based on the bimolecular affinity interaction with lectin or antibody. And the third type is based on the chemical covalent coupling to free side groups of surface-exposed proteins or carbohydrate chains, such as primary amines, carboxyl groups, glycan side chains. In addition, metabolic labeling and enzymatic reaction-based methods have also been employed to selectively isolate cell surface proteins. In this review, we will provide a comprehensive overview of the enrichment methods for cell surface proteome profiling.

SupraCells: Living Mammalian Cells Protected within Functional Modular Nanoparticle-Based Exoskeletons

Creating a synthetic exoskeleton from abiotic materials to protect delicate mammalian cells and impart them with new functionalities could revolutionize fields like cell-based sensing and create diverse new cellular phenotypes. Herein, the concept of "SupraCells," which are living mammalian cells encapsulated and protected within functional modular nanoparticle-based exoskeletons, is introduced. Exoskeletons are generated within seconds through immediate interparticle and cell/particle complexation that abolishes the macropinocytotic and endocytotic nanoparticle internalization pathways that occur without complexation. SupraCell formation is shown to be generalizable to wide classes of nanoparticles and various types of cells. It induces a spore-like state, wherein cells do not replicate or spread on surfaces but are endowed with extremophile properties, for example, resistance to osmotic stress, reactive oxygen species, pH, and UV exposure, along with abiotic properties like magnetism, conductivity, and multifluorescence. Upon decomplexation cells return to their normal replicative states. SupraCells represent a new class of living hybrid materials with a broad range of functionalities.

Photoluminescent organisms: how to make fungi glow through biointegration with lanthanide metal-organic frameworks

We show that filamentous fungi can emit green or red light after the accumulation of particulate lanthanide metal-organic frameworks over the cell wall. These new biohybrids present photoluminescence properties that are unaffected by the components of the cell wall. In addition, the fungal cells internalise lanthanide metal-organic framework particles, storing them into organelles, thereby making these materials promising for applications in living imaging studies.

Enzyme-Modulated Anaerobic Encapsulation of Chlorella Cells Allows Switching from O2 to H2 Production

Single-cell encapsulation has become an effective strategy in cell surface engineering; however, the construction of cell wall-like layers that allow the switching of the inherent functionality of the engineered cell is still rare. In this study, we show a universal way to create an enzyme-modulated oxygen-consuming sandwich-like layer by using polydopamine, laccase, and tannic acid as building blocks, which then could generate an anaerobic microenvironment around the cell. This layer protected the encapsulated C. pyrenoidosa cell against external stresses and enabled it to switch from normal photosynthetic O₂ production to photobiological H₂ production. The layer showed an smaller effect on the PSII activity, which contributed a significant enhancement on the rate (0.32 μmol H₂  h^-1  (mg chlorophyll)^-1 ) and the duration (7 d) of H₂ production. This strategy is expected to provide a pathway for modulating the functionality of cells and for breakthroughs in the development of green energy alternatives.

Simultaneous nutrient and carbon removal and electricity generation in self-buffered biocathode microbial fuel cell for high-salinity mustard tuber wastewater treatment

Mustard tuber wastewater (MTWW) was used as both anolyte and catholyte in biocathode microbial fuel cell (BMFC). The results showed simultaneous nutrient and carbon removal and electricity generation were realized in BMFC. Excellent Chemical Oxygen Demand (COD) removal occurred in both anode (>90%) and cathode (>91%). Concerning nutrient removal, it was mainly removed in cathode. The maximum total phosphorus (TP) removal could reach 80.8 ± 1.0% by biological action. Simultaneous nitrification and denitrification (SND) was realized in cathode. The bacteria involved in nitrification were Nitrosomonas and SM1A02. Oceanimonas and Saprospiraceae_uncultured (anaerobic denitrifier), Thauera, Stenotrophomonas, Flavobacterium and Marinobacter (aerobic denitrifier), and Thioalkalispira (autotrophic denitrifier) were responsible for denitrification. Considering slight variation of anode and cathode pH, it could be concluded that MTWW was adequately self-buffered when used as electrolyte. Furthermore, electricity generation decreased with cathodic dissolved oxygen (DO) declining. These findings provide a novel method for MTWW resourceful treatment.

Directional coupling in spatially distributed nanoreactors

Silica based hollow nanospheres filled with a reactant solution act as nanoreactors. A close packed ensemble of the nanoshells comprise a porous medium through which a chemical front can propagate. The front velocity decreases as the chemical signal, in the shape of a reaction-diffusion front, is transmitted from one sphere to the other due to the high curvature at the contact points. Experiments reveal that front propagation occurs through the cavity of the nanoshells because surface activity of filled nanoparticles itself cannot support chemical front across the medium.

Chemical front propagates through a closed-packed cluster of nanoreactors made of hollow nanoshells filled with reactant solution.

Polydopamine coating on individual cells for enhanced extracellular electron transfer

The double-mediator electron transport pathway was achieved by PDA coating on the surface of individual cells to facilitate EET.