Electronic communication of cells with a surface mediated by boronic acid saccharide interactions

Precise Generation of Selective Surface-Confined Glycoprotein Recognition Sites

Since glycoproteins have become increasingly recognized as key players in a wide variety of disease processes, there is an increasing need for advanced affinity materials for highly selective glycoprotein binding. Herein, for the first time, a surface-initiated controlled radical polymerization is integrated with supramolecular templating and molecular imprinting to yield highly reproducible synthetic recognition sites on surfaces with dissociation constants (K D) in the low micromolar range for target glycoproteins and minimal binding to nontarget glycoproteins. Importantly, it is shown that the synthetic strategy has a remarkable ability to distinguish the glycosylated and nonglycosylated forms of the same glycoprotein, with a >5-fold difference in binding affinity. The precise control over the polymer film thickness and positioning of multiple carbohydrate receptors plays a crucial role in achieving an enhanced affinity and selectivity. The generated functional materials of unprecedented glycoprotein recognition performance open up a wealth of opportunities in the biotechnological and biomedical fields.

Multiphoton fluorescence lifetime imaging microscopy (FLIM) and super-resolution fluorescence imaging with a supramolecular biopolymer for the controlled tagging of polysaccharides

A new supramolecular polysaccharide complex, comprising a functionalised coumarin tag featuring a boronic acid and β-d-glucan (a natural product extract from barley, Hordeum Vulgare) was assembled based on the ability of the boronate motif to specifically recognise and bind to 1,2- or 1,3-diols in water. The complexation ratio of the fluorophore : biopolymer strand was determined from fluorescence titration experiments in aqueous environments and binding isotherms best described this interaction using a 2 : 1 model with estimated association constants of K2:1a1 = 5.0 × 104 M-1 and K2:1a2 = 3.3 × 1011 M-1. The resulting hybrid (denoted 5@β-d-glucan) was evaluated for its cellular uptake as an intact functional biopolymer and its distribution compared to that of the pinacol-protected coumarin boronic acid derivative using two-photon fluorescence lifetime imaging microscopy (FLIM) in living cells. The new fluorescent β-d-glucan conjugate has a high kinetic stability in aqueous environments with respect to the formation of the free boronic acid derivative compound 5 and retains fluorescence emissive properties both in solution and in living cells, as shown by two-photon fluorescence spectroscopy coupled with time-correlated single photon counting (TCSPC). Super-resolution fluorescence imaging using Airyscan detection as well as TM AFM and Raman spectroscopy investigations confirmed the formation of fluorescent and nano-dimensional aggregates of up to 20 nm dimensions which self-assemble on several different inert surfaces, such as borosilicate glass and mica surfaces, and these aggregates can also be observed within living cells with optical imaging techniques. The cytoplasmic distribution of the 5@β-d-glucan complex was demonstrated in several different cancer cell lines (HeLa and PC-3) as well as in healthy cells (J774.2 macrophages and FEK-4). Both new compounds (pinacol protected boronated coumarin) 5-P and its complex hybrid 5@β-d-glucan successfully penetrate cellular membranes with the minimum morphological alterations to cells and distribute evenly in the cytoplasm. The glucan biopolymer retains its activity towards macrophages in the presence of the coumarin tag functionality, demonstrating the potential of this natural β-d-glucan to act as a functional self-assembled theranostic scaffold capable of mediating the delivery of anchored small organic molecules with imaging and drug delivery applications.

Extracellular electron transfer features of Gram-positive bacteria

Electroactive microorganisms possess the unique ability to transfer electrons to or from solid phase electron conductors, e.g., electrodes or minerals, through various physiological mechanisms. The processes are commonly known as extracellular electron transfer and broadly harnessed in microbial electrochemical systems, such as microbial biosensors, microbial electrosynthesis, or microbial fuel cells. Apart from a few model microorganisms, the nature of the microbe-electrode conductive interaction is poorly understood for most of the electroactive species. The interaction determines the efficiency and a potential scaling up of bioelectrochemical systems. Gram-positive bacteria generally have a thick electron non-conductive cell wall and are believed to exhibit weak extracellular electron shuttling activity. This review highlights reported research accomplishments on electroactive Gram-positive bacteria. The use of electron-conducting polymers as mediators is considered as one promising strategy to enhance the electron transfer efficiency up to application scale. In view of the recent progress in understanding the molecular aspects of the extracellular electron transfer mechanisms of Enterococcus faecalis, the electron transfer properties of this bacterium are especially focused on. Fundamental knowledge on the nature of microbial extracellular electron transfer and its possibilities can provide insight in interspecies electron transfer and biogeochemical cycling of elements in nature. Additionally, a comprehensive understanding of cell-electrode interactions may help in overcoming insufficient electron transfer and restricted operational performance of various bioelectrochemical systems and facilitate their practical applications.

Cell membrane engineering with synthetic materials: Applications in cell spheroids, cellular glues and microtissue formation

Biologically inspired materials with tunable bio- and physicochemical properties provide an essential framework to actively control and support cellular behavior. Cell membrane remodeling approaches benefit from the advances in polymer science and bioconjugation methods, which allow for the installation of un-/natural molecules and particles on the cells' surface. Synthetically remodeled cells have superior properties and are under intense investigation in various therapeutic scenarios as cell delivery systems, bio-sensing platforms, injectable biomaterials and bioinks for 3D bioprinting applications. In this review article, recent advances in the field of cell surface remodeling via bio-chemical means and the potential biomedical applications of these emerging cell hybrids are discussed. STATEMENT OF SIGNIFICANCE: Recent advances in bioconjugation methods, controlled/living polymerizations, microfabrication techniques and 3D printing technologies have enabled researchers to probe specific cellular functions and cues for therapeutic and research purposes through the formation of cell spheroids and polymer-cell chimeras. This review article highlights recent non-genetic cell membrane engineering strategies towards the fabrication of cellular ensembles and microtissues with interest in 3D in vitro modeling, cell therapeutics and tissue engineering. From a wider perspective, these approaches may provide a roadmap for future advances in cell therapies which will expedite the clinical use of cells, thereby improving the quality and accessibility of disease treatments.

Electrochemically stimulating developments in bioelectronic medicine

Cellular homeostasis is in part controlled by biological generated electrical activity. By interfacing biology with electronic devices this electrical activity can be modulated to actuate cellular behaviour. There are current limitations in merging electronics with biology sufficiently well to target and sense specific electrically active components of cells. By addressing this limitation, researchers give rise to new capabilities for facilitating the two-way transduction signalling mechanisms between the electronic and cellular components. This is required to allow significant advancement of bioelectronic technology which offers new ways of treating and diagnosing diseases. Most of the progress that has been achieved to date in developing bioelectronic therapeutics stimulate neural communication, which ultimately orchestrates organ function back to a healthy state. Some devices used in therapeutics include cochlear and retinal implants and vagus nerve stimulators. However, all cells can be impacted by electrical inputs which gives rise to the opportunity to broaden the use of bioelectronic medicine for treating disease. Electronic actuation of non-excitable cells has been shown to lead to ‘programmed’ cell behaviour via application of electronic input which alter key biological processes. A neglected form of cellular electrical communication which has not yet been considered when developing bioelectronic therapeutics is faradaic currents. These are generated during redox reactions. A precedent of electrochemical technology being used to modulate these reactions, thereby controlling cell behaviour, has already been set. In this mini review we highlight the current state of the art of electronic routes to modulating cell behaviour and identify new ways in which electrochemistry could be used to contribute to the new field of bioelectronic medicine.

Highly sensitive detection of cancer cells with an electrochemical cytosensor based on boronic acid functional polythiophene

The detection of cancer cells through important molecular recognition target such as sialic acid is significant for the clinical diagnosis and treatment. There are many electrochemical cytosensors developed for cancer cells detection but most of them have complicated fabrication processes which results in poor reproducibility and reliability. In this study, a simple, low-cost, and highly sensitive electrochemical cytosensor was designed based on boronic acid-functionalized polythiophene. In cytosensors fabrication simple single-step procedure was used which includes coating pencil graphite electrode (PGE) by means of electro-polymerization of 3-Thienyl boronic acid and Thiophen. Electrochemical impedance spectroscopy and cyclic voltammetry were used as an analytical methods to optimize and measure analytical performances of PGE/P(TBA_0.5Th_0.5) based electrode. Cytosensor showed extremely good analytical performances in detection of cancer cells with linear rage of 1×10¹ to 1×10⁶ cellsmL^-1 exhibiting low detection limit of 10 cellsmL^-1 and incubation time of 10min. Next to excellent analytical performances, it showed high selectivity towards AGS cancer cells when compared to HEK 293 normal cells and bone marrow mesenchymal stem cells (BM-hMSCs). This method is promising for future applications in early stage cancer diagnosis.

“Click-fluors”: triazole-linked saccharide sensors

A series of boronic acid-containing saccharide receptors was synthesised via copper catalysed azide–alkyne cycloaddition (CuAAC) reactions.

Boronic acids for fluorescence imaging of carbohydrates

Carbohydrate biomarkers are particularly important targets for fluorescence imaging given their pivotal role in numerous important biological events. This review highlights the development of fluorescence imaging agents based on boronic acids.