Phase Separation of DNA-Encoded Artificial Cells Boosts Signal Amplification for Biosensing

Transformative biomedical devices to overcome biomatrix effects

The emergence of high-performance biomedical devices and sensing technologies highlights the technological advancements in the field. Recently during COVID-19 pandemic, biosensors played an important role in medical diagnostics and disease monitoring. In the past few decades, biosensors have made impressive advances in terms of sensing capability, methodology, and applications, and modern biosensors show higher performance and functionality compared to traditional biosensing platforms. Currently, various biomedical devices are already in the market or on the verge of commercialization, such as disposable paper-based devices, lab-on-a-chip devices, wearable sensors, and artificial intelligence-assisted systems, all contributing to the evolution of digital health. Despite the promising features of detection methods for developing practical biosensors, there are substantial barriers to the commercialization of biomedical devices. An important challenge is the matrix effect in the detection of clinical samples. Although achieving low limit of detection values under controlled laboratory conditions is feasible, maintaining performance in real clinical samples is difficult. Matrix molecules present in these samples can interact with analytes, potentially affecting sensitivity, specificity, and sensor response. Approaches to reduce nonspecific adsorption and cross-reactivity are imperative for improving sensor performance. The detection of diagnostic biomarkers in complex biological matrices often requires laborious sample preparation, which may affect accuracy and precision. In this review, we highlight the recent efforts to detect analytes in real samples, both invasively and noninvasively, and underline technological advancements that mitigate the biomatrix effects. We also discuss commercially available biosensors and technologies promising commercial success, highlighting their potential effect on healthcare and diagnostics.

Cell-Targeting Bio-Catalytic Killer Protocell for High-Order Assembly Guided Cancer Cell Inhibition

The design and construction of synthetic therapeutic protocells capable of engaging in high-order assembly with living cells represent a significant challenge in synthetic biology and bioengineering. Inspired by cell membrane receptor-ligand systems, a protocell bioreactor is developed for targeted cancer cell elimination. This is achieved by constructing orthogonal, polysaccharide-based protocells (polysaccharidosomes, P-somes) through a bottom-up approach that leverages host-guest chemistry. The protocells are assembled via electrostatically-driven self-assembly of β-cyclodextrin (β-CD)-modified amino-dextran on a sacrificial template encapsulating glucose oxidase (GOx). To enable specific cancer cell targeting and catalytic activity, cell-targeting ligands (arginylglycylaspartic acid, cRGD) and catalase-like platinum-gold nanoparticles (Pt-AuNPs) are introduced through host-guest interactions, forming a fully functional, cell-targeting, bio-catalytic killer protocell. These protocells are programmed to spatially couple the GOx/Pt-AuNP catalytic reaction cascade. In the presence of glucose and hydroxyurea, this cascade generates a localized flux of nitric oxide (NO), which is exploited for in vitro cancer cell inhibition. Overall, the results highlight the potential of integrating orthogonal and synergistic tumor inhibition mechanisms within synthetic microcompartments. This platform demonstrates promise for future therapeutic applications, especially in cancer treatment, and represents a step forward in the development of programmable protocell-based therapeutic systems.

Aqueous Two-Phase Submicron Droplets Catalyze DNA Nanostructure Assembly for Confined Fluorescent Biosensing

Membraneless organelles (MLOs) are fundamental to cellular organization, enabling biochemical processes by concentrating biomolecules and regulating reactions within confined environments. While micrometer-scale synthetic droplets are extensively studied as models of MLOs, submicron droplets remain largely unexplored despite their potential to uniquely regulate biomolecular processes. Here, submicron droplets are generated by a polyethylene glycol (PEG)/dextran aqueous two-phase system (ATPS) as a model to investigate their effect on DNA assembly in crowded environments. The findings reveal that submicron droplets exhibit distinct advantages over microdroplets by acting as submicron catalytic centers that concentrate DNA and accelerate assembly kinetics. This enhancement is driven by a cooperative mechanism wherein global crowding from PEG induces an excluded volume effect, while local crowding from dextran provides weak but nonspecific interactions with DNA. By exploiting both the confinement and phase properties of submicron droplets, a rapid and sensitive assay is developed for miRNA detection using confined fluorescent readouts. These findings highlight the unique ability of submicron droplets to amplify biomolecular assembly processes, provide new insights into the interplay between global and local crowding effects in cellular-like environments, and present a platform for biomarker detection and visualization.

Orthogonal Host-Guest Interactions Enable Programming of Protocell Membranes for Cellular High-Order Assembly and Enhanced Immunogenicity

The complement system's distinguishing feature is its cell-specific surface ligands. However, the limited scalability and complexity of incorporating surface-customizable ligands into membrane-bound cell-like microassemblages have hindered their widespread adoption in synthetic biology and bioengineering. Here, we present a method for the batch construction of polysaccharide-based microcapsules (polysaccharidosomes, P-somes) with intrinsic functional host membranes capable of docking guest ligands via facile host-guest interactions. β-Cyclodextrin (β-CD) conjugated to the microcapsule membrane building block serves as the host entity for guest adamantane-linked functional molecules Cyanine5 (Cy5) and Pam3CSK4 (PAM). Interactive docking of either an aggregation agent, Cy5, or a Toll-like receptor agonist, Pam3CSK4, on P-somes followed by incubation with macrophages resulted in aggregation and immune activation of macrophages, respectively. The specificity of host-guest interactions allows for the expedited incorporation of additional functionalities into microassemblages. This can be instrumental in engineering cell-like membrane surfaces that replicate genuine cell-cell interactions, offering a unified platform for the development of micrometer-sized programmable therapeutic protocells.

Fabrication of Biomimetic Protocells via Interfacial Assembly of Protein-Lipid Nanoconjugates

The construction of functional, synthetic microcompartments is crucial for advancing our understanding of cellular processes and enhancing technological applications across various fields. This study introduces the creation of lipoproteinosomes, which are microscale compartments constructed from bovine serum albumin and stearoyl chloride (BSA-SC) nanoconjugates synthesized by employing thiourea-linkage chemistry. These spherical lipoproteinsomal microcapsules are formed through a water-in-oil Pickering emulsification process and stabilized in aqueous environments by cross-linking. The microcapsules not only exhibit capabilities to encapsulate and retain water-soluble macromolecules but also display enzyme-driven communication as protocells. This research not only underscores the potential of using natural amphiphilic compounds for constructing microcompartments but also highlights their broad applicability in biomedicine, protocell research, and microreactor technology.

Self-assembled bifunctional nanoflower-enabled CRISPR/Cas biosensing platform for dual-readout detection of Salmonella enterica

Sensitive detection and point-of-care test of bacterial pathogens is of great significance in safeguarding the public health worldwide. Inspired by the characteristics of horseradish peroxidase (HRP), we synthesized a hybrid nanoflower with peroxidase-like activity via a three-component self-assembled strategy. Interestingly, the prepared nanozyme not only could act as an alternative to HRP for colorimetric biosensing, but also function as a unique signal probe that could be recognized by a pregnancy test strip. By combining the bifunctional properties of hybrid nanoflower, isothermal amplification of LAMP, and the specific recognition and non-specific cleavage properties of CRISPR/Cas12a system, the dual-readout CRISPR/Cas12a biosensor was developed for sensitive and rapid detection of Salmonella enterica. Moreover, this platform in the detection of Salmonella enterica had limits of detection of 1 cfu/mL (colorimetric assay) in the linear range of 101-108 cfu/mL and 102 cfu/mL (lateral flow assay) in the linear range of 102-108 cfu/mL, respectively. Furthermore, the developed biosensor exhibited good recoveries in the spiked samples (lake water and milk) with varying concentrations of Salmonella enterica. This work provides new insights for the design of multifunctional nanozyme and the development of innovative dual-readout CRISPR/Cas system-based biosensing platform for the detection of pathogens.

Self-assembly of stabilized droplets from liquid-liquid phase separation for higher-order structures and functions

Dynamic microscale droplets produced by liquid-liquid phase separation (LLPS) have emerged as appealing biomaterials due to their remarkable features. However, the instability of droplets limits the construction of population-level structures with collective behaviors. Here we first provide a brief background of droplets in the context of materials properties. Subsequently, we discuss current strategies for stabilizing droplets including physical separation and chemical modulation. We also discuss the recent development of LLPS droplets for various applications such as synthetic cells and biomedical materials. Finally, we give insights on how stabilized droplets can self-assemble into higher-order structures displaying coordinated functions to fully exploit their potentials in bottom-up synthetic biology and biomedical applications.