Navigating the future: Microfluidics charting new routes in drug delivery

Microfluidics has emerged as a transformative force in the field of drug delivery, offering innovative avenues to produce a diverse range of nano drug delivery systems. Thanks to its precise manipulation of small fluid volumes and its exceptional command over the physicochemical characteristics of nanoparticles, this technology is notably able to enhance the pharmacokinetics of drugs. It has initiated a revolutionary phase in the domain of drug delivery, presenting a multitude of compelling advantages when it comes to developing nanocarriers tailored for the delivery of poorly soluble medications. These advantages represent a substantial departure from conventional drug delivery methodologies, marking a paradigm shift in pharmaceutical research and development. Furthermore, microfluidic platformsmay be strategically devised to facilitate targeted drug delivery with the objective of enhancing the localized bioavailability of pharmaceutical substances. In this paper, we have comprehensively investigated a range of significant microfluidic techniques used in the production of nanoscale drug delivery systems. This comprehensive review can serve as a valuable reference and offer insightful guidance for the development and optimization of numerous microfluidics-fabricated nanocarriers.

Engineering activatable promoters for scalable and multi-input CRISPRa/i circuits

Dynamic, multi-input gene regulatory networks (GRNs) are ubiquitous in nature. Multilayer CRISPR-based genetic circuits hold great promise for building GRNs akin to those found in naturally occurring biological systems. We develop an approach for creating high-performing activatable promoters that can be assembled into deep, wide, and multi-input CRISPR-activation and -interference (CRISPRa/i) GRNs. By integrating sequence-based design and in vivo screening, we engineer activatable promoters that achieve up to 1,000-fold dynamic range in an Escherichia coli-based cell-free system. These components enable CRISPRa GRNs that are six layers deep and four branches wide. We show the generalizability of the promoter engineering workflow by improving the dynamic range of the light-dependent EL222 optogenetic system from 6-fold to 34-fold. Additionally, high dynamic range promoters enable CRISPRa systems mediated by small molecules and protein-protein interactions. We apply these tools to build input-responsive CRISPRa/i GRNs, including feedback loops, logic gates, multilayer cascades, and dynamic pulse modulators. Our work provides a generalizable approach for the design of high dynamic range activatable promoters and enables classes of gene regulatory functions in cell-free systems.

CO2-elevated cell-free protein synthesis

Gases are the vital nutrition of all organisms as the precursor of metabolism pathways. As a potential biological process, protein synthesis is inevitably regulated by gas transport and utilization. However, the effect of carbon dioxide (CO₂) present in many metabolic pathways on protein synthesis has not been studied well. In this work, carbon dioxide combined with oxygen was employed for cell-free protein synthesis (CFPS) in the tube-in-tube reactor with precise control of gas concentration. In this in vitro system, gases could directly affect the protein synthesis process without transmembrane transport. Varied concentrations of carbon dioxide (0–1%) and constant oxygen concentration (21%) were employed for CFPS to assess the effects. The cell-free reactions with 0.3% CO₂ and 21% O₂ showed the highest protein yields. The combined effect of CO₂ and O₂ also resulted in relatively high protein expression under high oxygen conditions (0.3% CO₂ and 100% O₂). Moreover, metabolomics assays were performed to gain insight into metabolic changes, which showed that CO₂ slightly improved energy metabolism and redox balance. In particular, the extra supplied CO₂ activated the decarboxylating reactions and removed toxic metabolites to recover the protein synthesis activity. The exploration of CO₂ on protein synthesis could provide guiding implications for basic studies and biomanufacturing.

Biotechnology Applications of Cell-Free Expression Systems

Cell-free systems are a rapidly expanding platform technology with an important role in the engineering of biological systems. The key advantages that drive their broad adoption are increased efficiency, versatility, and low cost compared to in vivo systems. Traditionally, in vivo platforms have been used to synthesize novel and industrially relevant proteins and serve as a testbed for prototyping numerous biotechnologies such as genetic circuits and biosensors. Although in vivo platforms currently have many applications within biotechnology, they are hindered by time-constraining growth cycles, homeostatic considerations, and limited adaptability in production. Conversely, cell-free platforms are not hindered by constraints for supporting life and are therefore highly adaptable to a broad range of production and testing schemes. The advantages of cell-free platforms are being leveraged more commonly by the biotechnology community, and cell-free applications are expected to grow exponentially in the next decade. In this study, new and emerging applications of cell-free platforms, with a specific focus on cell-free protein synthesis (CFPS), will be examined. The current and near-future role of CFPS within metabolic engineering, prototyping, and biomanufacturing will be investigated as well as how the integration of machine learning is beneficial to these applications.

Microfluidics for Drug Development: From Synthesis to Evaluation

Drug development is a long process whose main content includes drug synthesis, drug delivery, and drug evaluation. Compared with conventional drug development procedures, microfluidics has emerged as a revolutionary technology in that it offers a miniaturized and highly controllable environment for bio(chemical) reactions to take place. It is also compatible with analytical strategies to implement integrated and high-throughput screening and evaluations. In this review, we provide a comprehensive summary of the entire microfluidics-based drug development system, from drug synthesis to drug evaluation. The challenges in the current status and the prospects for future development are also discussed. We believe that this review will promote communications throughout diversified scientific and engineering communities that will continue contributing to this burgeoning field.

Rapid RNase inhibitor production to enable low-cost, on-demand cell-free protein synthesis biosensor use in human body fluids

Human body fluids contain biomarkers which are used extensively for prognostication, diagnosis, monitoring, and evaluation of different treatments for a variety of diseases and disorders. The application of biosensors based on cell-free protein synthesis (CFPS) offers numerous advantages including on-demand and at-home use for fast, accurate detection of a variety of biomarkers in human fluids at an affordable price. However, current CFPS-based biosensors use commercial RNase inhibitors to inhibit different RNases present in human fluids and this reagent is approximately 90% of the expense of these biosensors. Here the flexible nature of Escherichia coli-lysate-based CFPS was used for the first time to produce murine RNase Inhibitor (m-RI) and to optimize its soluble and active production by tuning reaction temperature, reaction time, reduced potential, and addition of GroEL/ES folding chaperons. Furthermore, RNase inhibition activity of m-RI with the highest activity and stability was determined against increasing amounts of three human fluids of serum, saliva, and urine (0%-100% v/v) in lyophilized CFPS reactions. To further demonstrate the utility of the CFPS-produced m-RI, a lyophilized saliva-based glutamine biosensor was demonstrated to effectively work with saliva samples. Overall, the use of CFPS-produced m-RI reduces the total reagent costs of CFPS-based biosensors used in human body fluids approximately 90%.

Hydrofoam and oxygen headspace bioreactors improve cell-free therapeutic protein production yields through enhanced oxygen transport

Protein therapeutics are powerful tools in the fight against diabetes, cancers, growth disorders, and many other debilitating diseases. However, availability is limited due to cost and complications of production from living organisms. To make life-saving protein therapeutics more available to the world, the possibility of magistral or point-of-care protein therapeutic production has gained focus. The recent invention and optimization of lyophilized "cell-free" protein synthesis reagents and its demonstrated ability to produce highly active versions of FDA-approved cancer therapeutics have increased its potential for low-cost, single-batch, magistral medicine. Here we present for the first time the concept of increased oxygen mass transfer in small-batch, cell-free protein synthesis (CFPS) reactions through air-water foams. These "hydrofoam" reactions increased CFPS yields by up to 100%. Contrary to traditional protein synthesis using living organisms, where foam bubbles cause cell-lysis and production losses, hydrofoam CFPS reactions are "cell-free" and better tolerate foaming. Simulation and experimental results suggest that oxygen transfer is limiting in even small volume batch CFPS reactors and that the hydrofoam format improved oxygen transfer. This is further supported by CFPS reactions achieving higher yields when oxygen gas replaces air in the headspace of batch reactions. Improving CFPS yields with hydrofoam reduces the overall cost of biotherapeutic production, increasing availability to the developing world. Beyond protein therapeutic production, hydrofoam CFPS could also be used to enhance other CFPS applications including biosensing, biomanufacturing, and biocatalysis.

Accelerating gas-liquid chemical reactions in flow

Over the past decade, continuous flow reactors have emerged as a powerful tool for accelerated fundamental and applied studies of gas-liquid reactions, offering facile gas delivery and process intensification. In particular, unique features of highly gas-permeable tubular membranes in flow reactors (i.e., tube-in-tube flow reactor configuration) have been exploited as (i) an efficient analytic tool for gas-liquid solubility and diffusivity measurements and (ii) reliable gas delivery/generation strategy, providing versatile adaptability for a wide range of gas-liquid processes. The tube-in-tube flow reactors have been successfully adopted for rapid exploration of a wide range of gas-liquid reactions (e.g., amination, carboxylation, carbonylation, hydrogenation, ethylenation, oxygenation) using gaseous species both as the reactant and the product, safely handling toxic and flammable gases or unstable intermediate compounds. In this highlight, we present an overview of recent developments in the utilization of such intensified flow reactors within modular flow chemistry platforms for different gas-liquid processes involving carbon dioxide, oxygen, and other gases. We provide a detailed step-by-step guideline for robust assembly and safe operation of tube-in-tube flow reactors. We also discuss the current challenges and potential future directions for further development and utilization of tubular membrane-based flow reactors for gas-liquid processes.

O2-Tuned Protein Synthesis Machinery in Escherichia coli-Based Cell-Free System

Involved in most aerobic biochemical processes, oxygen affects cellular functions, and organism behaviors. Protein synthesis, as the underlying biological process, is unavoidably affected by the regulation of oxygen delivery and utilization. Bypassing the cell wall, cell-free protein synthesis (CFPS) systems are well adopted for the precise oxygen regulation analysis of bioprocesses. Here a reliable flow platform was developed for measuring and analyzing the oxygen regulation on the protein synthesis processes by combining Escherichia coli-based CFPS systems and a tube-in-tube reactor. This platform allows protein synthesis reactions conducted in precisely controlled oxygen concentrations. For analysis of the intrinsic role of oxygen in protein synthesis, O2-tuned CFPS systems were explored with transcription-translation related parameters (transcripts, energy, reactive oxygen species, and proteomic pathway analysis). It was found that 2% of oxygen was the minimum requirement for protein synthesis. There was translation-related protein degradation in the high oxygen condition leading to a reduction. By combining the precise gas level controlling and open biosystems, this platform is also potential for fundamental understanding and clinical applications by diverse gas regulation in biological processes.