Physiological validation of cell health upon probing with carbon nanotube endoscope and its benefit for single-cell interrogation

Single molecule delivery into living cells

Controlled manipulation of cultured cells by delivery of exogenous macromolecules is a cornerstone of experimental biology. Here we describe a platform that uses nanopipettes to deliver defined numbers of macromolecules into cultured cell lines and primary cells at single molecule resolution. In the nanoinjection platform, the nanopipette is used as both a scanning ion conductance microscope (SICM) probe and an injection probe. The SICM is used to position the nanopipette above the cell surface before the nanopipette is inserted into the cell into a defined location and to a predefined depth. We demonstrate that the nanoinjection platform enables the quantitative delivery of DNA, globular proteins, and protein fibrils into cells with single molecule resolution and that delivery results in a phenotypic change in the cell that depends on the identity of the molecules introduced. Using experiments and computational modeling, we also show that macromolecular crowding in the cell increases the signal-to-noise ratio for the detection of translocation events, thus the cell itself enhances the detection of the molecules delivered.

Revolutionizing cancer monitoring with carbon-based electrochemical biosensors

Cancer monitoring plays a critical role in improving patient outcomes by providing early detection, personalized treatment options, and treatment response tracking. Carbon-based electrochemical biosensors have emerged in recent years as a revolutionary technology with the potential to revolutionize cancer monitoring. These sensors are useful for clinical applications because of their high sensitivity, selectivity, rapid response, and compatibility with miniaturized equipment. This review paper gives an in-depth look at the latest developments and the possibilities of carbon-based electrochemical sensors in cancer surveillance. The essential principles of carbon-based electrochemical sensors are discussed, including their structure, operating mechanisms, and critical qualities that make them suited for cancer surveillance. Furthermore, we investigate their applicability in detecting specific cancer biomarkers, evaluating therapy responses, and detecting cancer recurrence early. Additionally, a comparison of carbon-based electrochemical sensor performance measures, including sensitivity, selectivity, accuracy, and limit of detection, is presented in contrast to existing monitoring methods and upcoming technologies. Finally, we discuss prospective tactics, future initiatives, and commercialization opportunities for improving the capabilities of these sensors and integrating them into normal clinical practice. The review highlights the potential impact of carbon-based electrochemical sensors on cancer diagnosis, treatment, and patient outcomes, as well as the importance of ongoing research, collaboration, and validation studies to fully realize their potential in revolutionizing cancer monitoring.

Development of multifunctional nanopipettes for controlled intracellular delivery and single-entity detection

The intracellular delivery of biomolecules and nanoscale materials to individual cells has gained remarkable attention in recent years owing to its wide applications in drug delivery, clinical diagnostics, bio-imaging and single-cell analysis. It remains a challenge to control and measure the delivered amount in one cell. In this work, we developed a multifunctional nanopipette - containing both a nanopore and nanoelectrode (pyrolytic carbon) at the apex - as a facile, minimally invasive and effective platform for both controllable single-cell intracellular delivery and single-entity counting. While controlled by a micromanipulator, the baseline changes of the nanopore ionic current (I) and nanoelectrode open circuit potential (V) help to guide the nanopipette tip insertion and positioning processes. The delivery from the nanopore barrel can be facilely controlled by the applied nanopore bias. To optimize the intracellular single-entity detection during delivery, we studied the effects of the nanopipette tip geometry and solution salt concentration in controlled experiments. We have successfully delivered gold nanoparticles and biomolecules into the cell, as confirmed by the increased scattering and fluorescence signals, respectively. The delivered entities have also been detected at the single-entity level using either one or both transient I and V signals. We found that the sensitivity of the single-entity electrochemical measurement was greatly affected by the local environment of the cell and varied between cell lines.

Methods for protein delivery into cells: from current approaches to future perspectives

The manipulation of cultured mammalian cells by the delivery of exogenous macromolecules is one of the cornerstones of experimental cell biology. Although the transfection of cells with DNA expressions constructs that encode proteins is routine and simple to perform, the direct delivery of proteins into cells has many advantages. For example, proteins can be chemically modified, assembled into defined complexes and subject to biophysical analyses prior to their delivery into cells. Here, we review new approaches to the injection and electroporation of proteins into cultured cells. In particular, we focus on how recent developments in nanoscale injection probes and localized electroporation devices enable proteins to be delivered whilst minimizing cellular damage. Moreover, we discuss how nanopore sensing may ultimately enable the quantification of protein delivery at single-molecule resolution.

Human Brain/Cloud Interface

The Internet comprises a decentralized global system that serves humanity's collective effort to generate, process, and store data, most of which is handled by the rapidly expanding cloud. A stable, secure, real-time system may allow for interfacing the cloud with the human brain. One promising strategy for enabling such a system, denoted here as a "human brain/cloud interface" ("B/CI"), would be based on technologies referred to here as "neuralnanorobotics." Future neuralnanorobotics technologies are anticipated to facilitate accurate diagnoses and eventual cures for the ∼400 conditions that affect the human brain. Neuralnanorobotics may also enable a B/CI with controlled connectivity between neural activity and external data storage and processing, via the direct monitoring of the brain's ∼86 × 109 neurons and ∼2 × 1014 synapses. Subsequent to navigating the human vasculature, three species of neuralnanorobots (endoneurobots, gliabots, and synaptobots) could traverse the blood-brain barrier (BBB), enter the brain parenchyma, ingress into individual human brain cells, and autoposition themselves at the axon initial segments of neurons (endoneurobots), within glial cells (gliabots), and in intimate proximity to synapses (synaptobots). They would then wirelessly transmit up to ∼6 × 1016 bits per second of synaptically processed and encoded human-brain electrical information via auxiliary nanorobotic fiber optics (30 cm3) with the capacity to handle up to 1018 bits/sec and provide rapid data transfer to a cloud based supercomputer for real-time brain-state monitoring and data extraction. A neuralnanorobotically enabled human B/CI might serve as a personalized conduit, allowing persons to obtain direct, instantaneous access to virtually any facet of cumulative human knowledge. Other anticipated applications include myriad opportunities to improve education, intelligence, entertainment, traveling, and other interactive experiences. A specialized application might be the capacity to engage in fully immersive experiential/sensory experiences, including what is referred to here as "transparent shadowing" (TS). Through TS, individuals might experience episodic segments of the lives of other willing participants (locally or remote) to, hopefully, encourage and inspire improved understanding and tolerance among all members of the human family.

Subcellular and in-vivo Nano-Endoscopy

Analysis of individual cells at the subcellular level is important for understanding diseases and accelerating drug discovery. Nanoscale endoscopes allow minimally invasive probing of individual cell interiors. Several such instruments have been presented previously, but they are either too complex to fabricate or require sophisticated external detectors because of low signal collection efficiency. Here we present a nanoendoscope that can locally excite fluorescence in labelled cell organelles and collect the emitted signal for spectral analysis. Finite Difference Time Domain (FDTD) simulations have shown that with an optimized nanoendoscope taper profile, the light emission and collection was localized within ~100 nm. This allows signal detection to be used for nano-photonic sensing of the proximity of fluorophores. Upon insertion into the individual organelles of living cells, the nanoendoscope was fabricated and resultant fluorescent signals collected. This included the signal collection from the nucleus of Acridine orange labelled human fibroblast cells, the nucleus of Hoechst stained live liver cells and the mitochondria of MitoTracker Red labelled MDA-MB-231 cells. The endoscope was also inserted into a live organism, the yellow fluorescent protein producing nematode Caenorhabditis elegans, and a fluorescent signal was collected. To our knowledge this is the first demonstration of in vivo, local fluorescence signal collection on the sub-organelle level.

High-Efficiency Gene Transfection of Cells through Carbon Nanotube Arrays

Introducing nucleic acids into mammalian cells is a crucial step to elucidate biochemical pathways, and to modify gene expression and cellular development in immortalized cells, primary cells, and stem cells. Current transfection technologies are time consuming and limited by the size of genetic cargo, the inefficient introduction of test molecules into large populations of target cells, and the cytotoxicity of the techniques. A novel method of introducing genes and biomolecules into tens of thousands of mammalian cells has been developed through an array of aligned hollow carbon nanotubes, manufactured by template-based nanofabrication processes, to achieve rapid high-efficiency transfer with low cytotoxicity. The utilization of carbon nanotube arrays for gene transfection overcomes molecular weight limits of current technologies and can be adapted to deliver drugs or proteins in addition to nucleic acids.

Nanoscale bio-platforms for living cell interrogation: current status and future perspectives

The living cell is a complex entity that dynamically responds to both intracellular and extracellular environments. Extensive efforts have been devoted to the understanding intracellular functions orchestrated with mRNAs and proteins in investigation of the fate of a single-cell, including proliferation, apoptosis, motility, differentiation and mutations. The rapid development of modern cellular analysis techniques (e.g. PCR, western blotting, immunochemistry, etc.) offers new opportunities in quantitative analysis of RNA/protein expression up to a single cell level. The recent entries of nanoscale platforms that include kinds of methodologies with high spatial and temporal resolution have been widely employed to probe the living cells. In this tutorial review paper, we give insight into background introduction and technical innovation of currently reported nanoscale platforms for living cell interrogation. These highlighted technologies are documented in details within four categories, including nano-biosensors for label-free detection of living cells, nanodevices for living cell probing by intracellular marker delivery, high-throughput platforms towards clinical current, and the progress of microscopic imaging platforms for cell/tissue tracking in vitro and in vivo. Perspectives for system improvement were also discussed to solve the limitations remains in current techniques, for the purpose of clinical use in future.

Bending spring rate investigation of nanopipette for cell injection

Bending of nanopipette tips during cell penetration is a major cause of cell injection failure. However, the flexural rigidity of nanopipettes is little known due to their irregular structure. In this paper, we report a quantitative method to estimate the flexural rigidity of a nanopipette by investigating its bending spring rate. First nanopipettes with a tip size of 300 nm are fabricated from various glass tubes by laser pulling followed by focused ion beam (FIB) milling. Then the bending spring rate of the nanopipettes is investigated inside a scanning electron microscope (SEM). Finally, a yeast cell penetration test is performed on these nanopipettes, which have different bending spring rates. The results show that nanopipettes with a higher bending spring rate have better cell penetration capability, which confirms that the bending spring rate may well reflect the flexural rigidity of a nanopipette. This method provides a quantitative parameter for characterizing the mechanical property of a nanopipette that can be potentially taken as a standard specification in the future. This general method can also be used to estimate other one-dimensional structures for cell injection, which will greatly benefit basic cell biology research and clinical applications.

Single-cell-precision microplasma-induced cancer cell apoptosis

The issue of single-cell control has recently attracted enormous interest. However, in spite of the presently achievable intracellular-level physiological probing through bio-photonics, nano-probe-based, and some other techniques, the issue of inducing selective, single-cell-precision apoptosis, without affecting neighbouring cells remains essentially open. Here we resolve this issue and report on the effective single-cell-precision cancer cell treatment using the reactive chemistry of the localized corona-type plasma discharge around a needle-like electrode with the spot size ∼1 µm. When the electrode is positioned with the micrometer precision against a selected cell, a focused and highly-localized micro-plasma discharge induces apoptosis in the selected individual HepG2 and HeLa cancer cells only, without affecting any surrounding cells, even in small cell clusters. This is confirmed by the real-time monitoring of the morphological and structural changes at the cellular and cell nucleus levels after the plasma exposure.

One-dimensional nanoprobes for single-cell studies

Owing to variation of individual cells within a population, single-cell studies are of great interest to researchers. Recent developments in nanofabrication technology have made this area increasingly attractive as one-dimensional (1D) nanoscale probes can be manufactured with increasing accuracy. Here, we provide an overview and description of the major designs that have been reported to date. For more details of what applications could be realized and how, based on the probe shapes and designs, we summarize the most recently reported performances of 1D single-cell probes with their advantages and limitations. Minimally invasive probes are required for long-term experiments on single cells. Carbon nanotubes with their unique properties and structure are excellent candidates for multitask robotic intracellular probes. Carbon nanotube-tipped cellular endoscopes are less invasive compared with pipettes or cantilever tips. Advances in nanofabrication techniques have made it possible to produce more consistent nanoscale cellular probes that can capture a variety of information from optical, electrical and chemical signals. In addition, these tools can transfer tiny amounts of fluids and molecular materials in a highly localized fashion for the purpose of analyzing or stimulating a variety of responses at the level of individual cells and even cellular organelles. We conclude with a critical analysis of the current state of the field as well as the major obstacles for further probe development of minimally invasive probes and their widespread use in cell biology.

Optimization of light delivery by a nanowire-based single cell optical endoscope

Here we present a new design and FDTD simulations of light delivery by a nanowire-based intracellular endoscope. Nanowires can be used for minimally invasive and very local light delivery inside cells. One of the main challenges is coupling of light into the nanowire. We propose a new plasmonic coupler interface between cleaved optical fiber and a nanowire, and optimize light coupling efficiency and contrast.

Multifunctional ferromagnetic disks for modulating cell function

In this work, we focus on the methods for controlling cell function with ferromagnetic disk-shaped particles. We will first review the history of magnetically assisted modulation of cell behavior and applications of magnetic particles for studying physical properties of a cell. Then, we consider the biological applications of the microdisks such as the method for induction of cancer cell apoptosis, controlled drug release, hyperthermia and MRI imaging.