Genetically Engineered Bacterial Biohybrid Microswimmers for Sensing Applications

Colloidal Active Matter Mimics the Behavior of Biological Microorganisms-An Overview

This article provides a review of the recent development of biomimicking behaviors in active colloids. While the behavior of biological microswimmers is undoubtedly influenced by physics, it is frequently guided and manipulated by active sensing processes. Understanding the respective influences of the surrounding environment can help to engineering the desired response also in artificial swimmers. More often than not, the achievement of biomimicking behavior requires the understanding of both biological and artificial microswimmers swimming mechanisms and the parameters inducing mechanosensory responses. The comparison of both classes of microswimmers provides with analogies in their dependence on fuels, interaction with boundaries and stimuli induced motion, or taxis.

Directed Autonomous Motion and Chiral Separation of Self-Propelled Janus Particles in Convection Roll Arrays

Self-propelled Janus particles exhibit autonomous motion thanks to engines of their own. However, due to the randomly changing direction of such motion they are of little use for emerging nanotechnological and biomedical applications. Here, we numerically show that the motion of chiral active Janus particles can be directed, subjecting them to a linear array of convection rolls. The rectification power of self-propulsion motion here can be made to be more than 60%, which is much larger than earlier reports. We show that rectification of a chiral Janus particle's motion leads to conspicuous segregation of dextrogyre and levogyre active particles from a racemic binary mixture. Further, we demonstrate how efficiently the rectification effect can be exploited to separate dextrogyre and levogyre particles when their intrinsic torques are distributed with Gaussian statistics.

Biocompatible micromotors for biosensing

Micro/nanomotors are nanoscale devices that have been explored in various fields, such as drug delivery, environmental remediation, or biosensing and diagnosis. The use of micro/nanomotors has grown considerably over the past few years, partially because of the advantages that they offer in the development of new conceptual avenues in biosensing. This is due to their propulsion and intermixing in solution compared with their respective static forms, which enables motion-based detection methods and/or decreases bioassay time. This review focuses on the impacts of micro/nanomotors on biosensing research in the last 2 years. An overview of designs for bioreceptor attachment to micro/nanomotors is given. Recent developments have focused on chemically propelled micromotors using external fuels, commonly hydrogen peroxide. However, the associated fuel toxicity and inconvenience of use in relevant biological samples such as blood have prompted researchers to explore new micro/nanomotor biosensing approaches based on biocompatible propulsion sources such as magnetic or ultrasound fields. The main advances in biocompatible propulsion sources for micro/nanomotors as novel biosensing platforms are discussed and grouped by their propulsion-driven forces. The relevant analytical applications are discussed and representatively illustrated. Moreover, envisioning future biosensing applications, the principal advantages of micro/nanomotor synthesis using biocompatible and biodegradable materials are given. The review concludes with a realistic drawing on the present and future perspectives.

Engineered Bacteria-Based Living Materials for Biotherapeutic Applications

Future advances in therapeutics demand the development of dynamic and intelligent living materials. The past static monofunctional materials shall be unable to meet the requirements of future medical development. Also, the demand for precision medicine has increased with the progressively developing human society. Therefore, engineered living materials (ELMs) are vitally important for biotherapeutic applications. These ELMs can be cells, microbes, biofilms, and spores, representing a new platform for treating intractable diseases. Synthetic biology plays a crucial role in the engineering of these living entities. Hence, in this review, the role of synthetic biology in designing and creating genetically engineered novel living materials, particularly bacteria, has been briefly summarized for diagnostic and targeted delivery. The main focus is to provide knowledge about the recent advances in engineered bacterial-based therapies, especially in the treatment of cancer, inflammatory bowel diseases, and infection. Microorganisms, particularly probiotics, have been engineered for synthetic living therapies. Furthermore, these programmable bacteria are designed to sense input signals and respond to disease-changing environments with multipronged therapeutic outputs. These ELMs will open a new path for the synthesis of regenerative medicines as they release therapeutics that provide in situ drug delivery with lower systemic effects. In last, the challenges being faced in this field and the future directions requiring breakthroughs have been discussed. Conclusively, the intent is to present the recent advances in research and biomedical applications of engineered bacteria-based therapies during the last 5 years, as a novel treatment for uncontrollable diseases.

Prospects and applications of synergistic noble metal nanoparticle-bacterial hybrid systems

Hybrid systems composed of living cells and nanomaterials have been attracting great interest in various fields of research ranging from materials science to biomedicine. In particular, the interfacing of noble metal nanoparticles and bacterial cells in a single architecture aims to generate hybrid systems that combine the unique physicochemical properties of the metals and biological attributes of the microbial cells. While the bacterial cells provide effector and scaffolding functions, the metallic component endows the hybrid system with multifunctional capabilities. This synergistic effort seeks to fabricate living materials with improved functions and new properties that surpass their individual components. Herein, we provide an overview of this research field and the strategies for obtaining hybrid systems, and we summarize recent biological applications, challenges and current prospects in this exciting new arena.

Bacteria biohybrid oral vaccines for colorectal cancer treatment reduce tumor growth and increase immune infiltration

Bacteria biohybrid-based vaccine delivery systems, which integrate a vaccine carrier with live non-pathogenic bacteria, are hypothesized to have improved immunostimulating potential. The aim of this study was to develop oral bacteria biohybrid-based vaccines to treat a mouse model of colorectal cancer. E. coli were combined with tumor antigen- and adjuvant-containing emulsions or liposomes. Emulsion and liposome biohybrid vaccines demonstrated in vitro and in vivo therapeutic potential. Bacteria biohybrid vaccines significantly increased the expression of CD40⁺, CD80⁺ and CD86⁺ on murine bone marrow-derived dendritic cells. Mice vaccinated with emulsion biohybrid vaccines had an increased CD8⁺ T cell infiltration into tumors and developed three-fold smaller tumors compared to the mice that received emulsion vaccine without E. coli.

Recent Advances in Microswimmers for Biomedical Applications

Microswimmers are a rapidly developing research area attracting enormous attention because of their many potential applications with high societal value. A particularly promising target for cleverly engineered microswimmers is the field of biomedical applications, where many interesting examples have already been reported for e.g., cargo transport and drug delivery, artificial insemination, sensing, indirect manipulation of cells and other microscopic objects, imaging, and microsurgery. Pioneered only two decades ago, research studies on the use of microswimmers in biomedical applications are currently progressing at an incredibly fast pace. Given the recent nature of the research, there are currently no clinically approved microswimmer uses, and it is likely that several years will yet pass before any clinical uses can become a reality. Nevertheless, current research is laying the foundation for clinical translation, as more and more studies explore various strategies for developing biocompatible and biodegradable microswimmers fueled by in vivo-friendly means. The aim of this review is to provide a summary of the reported biomedical applications of microswimmers, with focus on the most recent advances. Finally, the main considerations and challenges for clinical translation and commercialization are discussed.