A Stimuli-Responsive, Binary Reagent System for Rapid Isolation of Protein Biomarkers

Unveiling the Complex World of Extracellular Vesicles: Novel Characterization Techniques and Manufacturing Considerations

Extracellular vesicles (EVs) function as potent mediators of intercellular communication for many in vivo processes, contributing to both health and disease related conditions. Given their biological origins and diverse functionality from correspondingly unique "cargo" compositions, both endogenous and modified EVs are garnering attention as promising therapeutic modalities and vehicles for targeted therapeutic delivery applications. Their diversity in composition, however, has revealed a significant need for more comprehensive analytical-based characterization methods, and manufacturing processes that are consistent and scalable. In this review, we explore the dynamic landscape of EV research and development efforts, ranging from novel isolation approaches, to their analytical assessment through novel characterization techniques, and to their production by industrial-scale manufacturing process considerations. Expanding the horizon of these topics to EVs for in-human applications, we underscore the need for stringent development and adherence to Good Manufacturing Practice (GMP) guidelines. Wherein, the intricate interplay of raw materials, production in bioreactors, and isolation practices, along with analytical assessments compliant with the Minimal Information for Studies of Extracellular Vesicles (MISEV) guidelines, in conjunction with reference standard materials, collectively pave the way for standardized and consistent GMP production processes.

A simple agglutination system for rapid antigen detection from large sample volumes with enhanced sensitivity

Lateral flow assays (LFAs) provide a simple and quick option for diagnosis and are widely adopted for point-of-care or at-home tests. However, their sensitivity is often limited. Most LFAs only allow 50 μL samples while various sample types such as saliva could be collected in much larger volumes. Adapting LFAs to accommodate larger sample volumes can improve assay sensitivity by increasing the number of target analytes available for detection. Here, a simple agglutination system comprising biotinylated antibody (Ab) and streptavidin (SA) is presented. The Ab and SA agglutinate into large aggregates due to multiple biotins per Ab and multiple biotin binding sites per SA. Dynamic light scattering (DLS) measurements showed that the agglutinated aggregate could reach a diameter of over 0.5 μm and over 1.5 μm using poly-SA. Through both experiments and Monte Carlo modeling, we found that high valency and equivalent concentrations of the two aggregating components were critical for successful agglutination. The simple agglutination system enables antigen capture from large sample volumes with biotinylated Ab and a swift transition into aggregates that can be collected via filtration. Combining the agglutination system with conventional immunoassays, an agglutination assay is proposed that enables antigen detection from large sample volumes using an in-house 3D-printed device. As a proof-of-concept, we developed an agglutination assay targeting SARS-CoV-2 nucleocapsid antigen for COVID-19 diagnosis from saliva. The assay showed a 10-fold sensitivity enhancement when increasing sample volume from 50 μL to 2 mL, with a final limit of detection (LoD) of 10 pg mL-1 (∼250 fM). The assay was further validated in negative saliva spiked with gamma-irradiated SARS-CoV-2 and showed an LoD of 250 genome copies per μL. The proposed agglutination assay can be easily developed from existing LFAs to facilitate the processing of large sample volumes for improved sensitivity.

State of the art on the separation and purification of proteins by magnetic nanoparticles

The need for excellent, affordable, rapid, reusable and biocompatible protein purification techniques is justified based on the roles of proteins as key biomacromolecules. Magnetic nanomaterials nowadays have become the subject of discussion in proteomics, drug delivery, and gene sensing due to their various abilities including rapid separation, superparamagnetism, and biocompatibility. These nanomaterials also referred to as magnetic nanoparticles (MNPs) serve as excellent options for traditional protein separation and analytical methods because they have a larger surface area per volume. From ionic metals to carbon-based materials, MNPs are easily functionalized by modifying their surface to precisely recognize and bind proteins. This review excavates state-of-the-art MNPs and their functionalizing agents, as efficient protein separation and purification techniques, including ionic metals, polymers, biomolecules, antibodies, and graphene. The MNPs could be reused and efficaciously manipulated with these nanomaterials leading to highly improved efficiency, adsorption, desorption, and purity rate. We also discuss the binding and selectivity parameters of the MNPs, as well as their future outlook. It is concluded that parameters like charge, size, core-shell, lipophilicity, lipophobicity, and surface energy of the MNPs are crucial when considering protein selectivity, chelation, separation, and purity.

Exosome Processing and Characterization Approaches for Research and Technology Development

Exosomes are extracellular vesicles that share components of their parent cells and are attractive in biotechnology and biomedical research as potential disease biomarkers as well as therapeutic agents. Crucial to realizing this potential is the ability to manufacture high-quality exosomes; however, unlike biologics such as proteins, exosomes lack standardized Good Manufacturing Practices for their processing and characterization. Furthermore, there is a lack of well-characterized reference exosome materials to aid in selection of methods for exosome isolation, purification, and analysis. This review informs exosome research and technology development by comparing exosome processing and characterization methods and recommending exosome workflows. This review also provides a detailed introduction to exosomes, including their physical and chemical properties, roles in normal biological processes and in disease progression, and summarizes some of the on-going clinical trials.

A thermo-responsive, self-assembling biointerface for on demand release of surface-immobilised proteins

Dedicated chemistries for on-demand capture and release of biomolecules at the solid-liquid interface are required for applications in drug delivery, for the synthesis of switchable surfaces used in analytical devices and for the assembly of next-generation biomaterials with complex architectures and functions. Here we report the engineering of a binary self-assembling polypeptide system for reversible protein capture, immobilisation and controlled thermo-responsive release from a solid surface. The first element of the binary system is a universal protein substrate immobilised on a solid surface. This protein is bio-inspired by the neuronal SNAP25, which is the protein involved in the docking and fusion of synaptic vesicles to the synaptic membrane. The second element is an artificial chimeric protein engineered to include distinct domains from three different proteins: Syntaxin, VAMP and SNAP25. These native proteins constitute the machinery dedicated to vesicle trafficking in eukaryotes. We removed approximately 70% of native protein sequence from these proteins and constructed a protein chimera capable of high affinity interaction and self-assembly with immobilised substrate. The interaction of the two parts of the engineered protein complex is strong but fully-reversible and therefore the chimera can be recombinantly fused as a tag to a protein of interest, to allow spontaneous assembly and stimuli-sensitive release from the surface upon heating at a predetermined temperature. Two thermo-responsive tags are reported: the first presents remarkable thermal stability with melting temperature of the order of 80 °C; the second disassembles at a substantially lower temperature of about 45 °C. The latter is a promising candidate for remote-controlled localised delivery of therapeutic proteins, as physiologically tolerable local increase of temperatures in the 40-45 °C range can be achieved using magnetic fields, infra-red light or focused ultrasound. Importantly, these two novel polypeptides provide a broader blueprint for the engineering of future functional proteins with predictable folding and response to external stimuli.

Recent Advances in Biosensors for Nucleic Acid and Exosome Detection

Biosensors are analytical devices for biomolecule detection that compromise three essential components: recognition moiety, transducer, and signal processor. The sensor converts biomolecule recognition to detectable signals, which has been applied in diverse fields such as clinical monitoring, in vitro diagnostics, food industry etc. Based on signal transduction mechanisms, biosensors can be categorized into three major types: optical biosensors, electrochemical biosensors, and mass-based biosensors. Recently, the need for faster, more sensitive detection of biomolecules has compeled researchers to develop various sensing techniques. In this review, the basic structure and sensing principles of biosensors are introduced. Additionally, the review discusses multiple recent works about nucleic acid and exosome sensing.

Temperature-Responsive Magnetic Nanoparticles for Enabling Affinity Separation of Extracellular Vesicles

Small magnetic nanoparticles that have surfaces decorated with stimuli-responsive polymers can be reversibly aggregated via a stimulus, such as temperature, to enable efficient and rapid biomarker separation. To fully realize the potential of these particles, the synthesis needs to be highly reproducible and scalable to large quantity. We have developed a new synthesis for temperature-responsive magnetic nanoparticles via an in situ co-precipitation process of Fe2+/Fe3+ salts at room temperature with poly(acrylic acid)- block-poly( N-isopropylacrylamide) diblock co-polymer template, synthesized via the reversible addition-fragmentation chain-transfer polymerization method. These particles were 56% polymer by weight with a 6.5:1 Fe/COOH ratio and demonstrated remarkable stability over a 2 month period. The hydrodynamic diameter remained constant at ∼28 nm with a consistent transition temperature of 34 °C, and the magnetic particle separation efficiency at 40 °C was ≥95% over the 2 month span. These properties were maintained for all large-scale synthesis batches. To demonstrate the practical utility of the stimuli-responsive magnetic nanoparticles, the particles were incorporated into a temperature-responsive binary reagent system and efficiently separated a model protein biomarker (mouse IgG) as well as purified extracellular vesicles derived from a human biofluid, seminal plasma. The ease of using these particles will prove beneficial for various biomedical applications.

The emerging role of nanomaterials in immunological sensing - a brief review

Nanomaterials are beginning to play an important role in the next generation of immunological assays and biosensors, with potential impacts both in research and clinical practice. In this brief review, we highlight two areas in which nanomaterials are already making new and important contributions in the past 5-10 years: firstly, in the improvement of assay and biosensor sensitivity for detection of low abundance proteins of immunological significance, and secondly, in the real-time and continuous monitoring of protein secretion from arrays of individual cells. We finish by challenging the immunology/sensing communities to work together to develop nanomaterials that can provide real-time, continuous, and sensitive molecular readouts in vivo, a lofty goal that will require significant collaborative effort.

New Combination/Application of Polymer-Based Nanoparticles for Biomedical Engineering

Polymer-based nanoparticles (PNPs) are attractive in part due to their ultra-small size, versatility and target specificity. Therefore, PNPs have been increasingly used in a variety of biomedical applications including diagnoses and therapeutic treatment. In this chapter, we focus on the recent studies (within 5 years) with some new ideas/agent's application in biomedical field and roughly divide applications of PNPs into four categories: (1) Delivery, (2) In vivo imaging, (3) Therapies, and (4) Other applications. First, we introduce how PNPs can enhance the treatment and delivery efficiency of therapeutic agent. Second, how PNPs can be used to help in vivo imaging system for disease tracking and monitor. Then, we reveal some novel PNPs which is able to function as an agent in photodynamic, photothermal, sonodynamic and neuron capture therapy. Furthermore, we also mention some interesting applications of PNPs for biomedical field in individual form or cluster employment, such as immunoswitch particles, surface fabrication. Finally, the challenges and future development of PNPs are also discussed. In delivery section, we focus on how polymer "can be used" as vehicles in delivery application. But, in the section of imaging and therapies, we carried on how polymer as an "adjuvant" for functional enhancement. The biodegradable property of PNPs is the feature that they can be controllable for itself degradation and drug release as a chief actor. Besides, in imaging and therapies application, PNPs can be the support role for helping contrast agent or photo/sonosensitizer to enlarge their imaging or therapeutic effect.

Magnetic Separation of Elastin-like Polypeptide Receptors for Enrichment of Cellular and Molecular Targets

Protein-conjugated magnetic nanoparticles (mNPs) are promising tools for a variety of biomedical applications, from immunoassays and biosensors to theranostics and drug-delivery. In such applications, conjugation of affinity proteins (e.g., antibodies) to the nanoparticle surface many times compromises biological activity and specificity, leading to increased reagent consumption and decreased assay performance. To address this problem, we engineered a biomolecular magnetic separation system that eliminates the need to chemically modify nanoparticles with the capture biomolecules or synthetic polymers of any kind. The system consists of (i) thermoresponsive magnetic iron oxide nanoparticles displaying poly(N-isopropylacrylamide) (pNIPAm), and (ii) an elastin-like polypeptide (ELP) fused with the affinity protein Cohesin (Coh). Proper design of pNIPAm-mNPs and ELP-Coh allowed for efficient cross-aggregation of the two distinct nanoparticle types under collapsing stimuli, which enabled magnetic separation of ELP-Coh aggregates bound to target Dockerin (Doc) molecules. Selective resolubilization of the ELP-Coh/Doc complexes was achieved under intermediate conditions under which only the pNIPAm-mNPs remained aggregated. We show that ELP-Coh is capable of magnetically separating and purifying nanomolar quantities of Doc as well as eukaryotic whole cells displaying the complementary Doc domain from diluted human plasma. This modular system provides magnetic enrichment and purification of captured molecular targets and eliminates the requirement of biofunctionalization of magnetic nanoparticles to achieve bioseparations. Our streamlined and simplified approach is amenable for point-of-use applications and brings the advantages of ELP-fusion proteins to the realm of magnetic particle separation systems.

Efficient Enrichment and Analyses of Bacteria at Ultralow Concentration with Quick-Response Magnetic Nanospheres

Enrichment and purification of bacteria from complex matrices are crucial for their detection and investigation, in which magnetic separation techniques have recently show great application advantages. However, currently used magnetic particles all have their own limitations: Magnetic microparticles exhibit poor binding capacity with targets, while magnetic nanoparticles suffer slow magnetic response and high loss rate during treatment process. Herein, we used a highly controllable layer-by-layer assembly method to fabricate quick-response magnetic nanospheres (MNs), and with Salmonella typhimurium as a model, we successfully achieve their rapid and efficient enrichment. The MNs combined the advantages of magnetic microparticles and nanoparticles. On the one hand, the MNs had a fast magnetic response, and almost 100% of the MNs could be recovered by 1 min attraction with a simple magnetic scaffold. Hence, using antibody conjugated MNs (immunomagnetic nanospheres, IMNs) to capture bacteria hardly generated loss and did not need complex separation tools or techniques. On the other hand, the IMNs showed much excellent capture capacity. With 20 min interaction, almost all of the target bacteria could be captured, and even only one bacterium existing in the samples was not missed, comparing with the immunomagnetic microparticles which could only capture less than 50% of the bacteria. Besides, the IMNs could achieve the same efficient enrichment in complex matrices, such as milk, fetal bovine serum, and urine, demonstrating their good stability, strong anti-interference ability, and low nonspecific adsorption. In addition, the isolated bacteria could be directly used for culture, polymerase chain reaction (PCR) analyses, and fluorescence immunoassay without a release process, which suggested our IMNs-based enrichment strategy could be conveniently coupled with the downstream identification and analysis techniques. Thus, the MNs provided by this work showed great superiority in bacteria enrichment, which would be a promising tool for bacteria detection and investigation.