Repeated photoporation with graphene quantum dots enables homogeneous labeling of live cells with extrinsic markers for fluorescence microscopy

A mini-review on gene delivery technique using nanoparticles-mediated photoporation induced by nanosecond pulsed laser

Nanosecond pulsed laser induced photoporation has gained increasing attention from scholars as an effective method for delivering the membrane-impermeable extracellular materials into living cells. Compared with femtosecond laser, nanosecond laser has the advantage of high throughput and low costs. It also has a higher delivery efficiency than continuous wave laser. Here, we provide an extensive overview of current status of nanosecond pulsed laser induced photoporation, covering the photoporation mechanism as well as various factors that impact the delivery efficiency of photoporation. Additionally, we discuss various techniques for achieving photoporation, such as direct photoporation, nanoparticles-mediated photoporation and plasmonic substrates mediated photoporation. Among these techniques, nanoparticles-mediated photoporation is the most promising approach for potential clinical application. Studies have already been reported to safely destruct the vitreous opacities in vivo by nanosecond laser induced vapor nanobubble. Finally, we discuss the potential of nanosecond laser induced phototoporation for future clinical applications, particularly in the areas of skin and ophthalmic pathologies. We hope this review can inspire scientists to further improve nanosecond laser induced photoporation and facilitate its eventual clinical application.

A live mammalian cells electroporation array for on-chip immunofluorescence

The detection of intracellular proteins in vitro is commonly realized with immunofluorescence techniques, through which antibodies or markers are delivered into fixed cells and recognize specific proteins. Many innovative techniques, however, avoid cells fixation by chemical compounds and, among the others, electroporation is widely used. Here we demonstrate that in situ electroporation on thin film SiO2 capacitive microelectrodes can be realized with high efficiency to deliver fluorescent markers and antibodies into mammalian cell lines and primary neuronal cells to detect intracellular proteins, like actin. The results presented in this work open the way to the use of this technique for the detection of potentially any target protein, even through subsequent electroporations.

The importance of cell uptake in photothermal treatments mediated by biomimetic magnetic nanoparticles

Biomimetic magnetic nanoparticles (BMNPs) mediated by MamC have proven to be photothermal agents able to allow an optimized cytotoxicity against tumoral cells when used simultaneously as drug nanotransporters and as hyperthermia agents. However, it remains unclear whether BMNPs need to be internalized by the cells and/or if there is a threshold for internal Fe concentration for the photothermal therapy to be effective. In this study, three different situations for photothermal treatments have been simulated to disentangle the effect of BMNPs cell uptake on cell viability after photothermal treatments. Human hepatoblastoma (HepG2) cell line was treated with suspensions of BMNPs, and protocols were developed to have only intracellular BMNPs, only extracellular BMNPs or both, followed by photothermal exposure of the treated cell cultures. Our data demonstrate that: (1) Although the heating efficiency of the photothermal agent is not altered by its location (intra/extracellular), the intracellular location of BMNPs is crucial to ensure the cytotoxic effect of photothermal treatments, especially at low Fe concentration. In fact, the concentration of BMNPs needed to reach the same cytotoxic effect following upon laser irradiation of 0.2 W/cm2 is three times larger if BMNPs are located extracellularly compared to that needed if BMNPs are located intracellularly; (2) For a given location of the BMNPs, cell death increases with BMNPs (or Fe) concentration. When BMNPs are located intracellularly, there is a threshold for Fe concentration (∼ 0.5 mM at laser power intensities of 0.1 W/cm2) needed to affect cell viability following upon cell exposure to photothermia. (3) Bulk temperature rise is not the only factor accounting for cell death. Actually, temperature increases inside the cells cause more damage to cell structures and trigger cell death more efficiently than an increase in the temperature outside the cell.

Upconverting-photon quenching-mediated perforation influx as an intracellular delivery method using posAuNP@UCNPs nanocomposites for osteoarthritis treatment

Photoporation techniques based on plasmonic nanoparticles such as gold nanoparticles have been extensively studied for the intracellular delivery of substances via cell membrane disruption. However, the clinical application of AuNP is challenging due to its absorption in the 500 nm region of the light spectrum. To overcome this challenge, upconversion nanoparticles were employed to stimulate AuNP at NIR wavelengths. posAuNP@UCNPs nanocomposites were produced by coating 30 nm UCNPs on 80 nm AuNPs using DOPA-PEI, which were then irradiated with 980 nm NIR light to facilitate their intracellular delivery. TEM and DLS confirmed that posAuNP and UCNP combine to form nanocomposites. Additionally, multiphysics simulation was used to analyze the distribution of the posAuNP electric field based on morphological differences that change as the UCNP ratio increases. Next, effective LED irradiation conditions were established by applying upconverting-photon quenching-mediated perforation influx to C28/I2 cells as suspensions or spheroids. posAuNP@UCNP nanocomposites were confirmed to be effective for the delivery of baricitinib as a treatment for osteoarthritis in a three-dimensional osteoarthritis model. Finally, chondrocyte differentiation was induced through intracellular delivery of baricitinib using posAuNP@UCNPs. The findings suggest that posAuNP@UCNPs have great potential as a tool for non-invasive drug delivery via UCPPin.

Intracellular protein delivery: New insights into the therapeutic applications and emerging technologies

The inability to cross the plasma membranes traditionally limited the therapeutic use of recombinant proteins. However, in the last two decades, novel technologies made delivering proteins inside the cells possible. This allowed researchers to unlock intracellular targets, once considered 'undruggable', bringing a new research area to emerge. Protein transfection systems display a large potential in a plethora of applications. However, their modality of action is often unclear, and cytotoxic effects are elevated, whereas experimental conditions to increase transfection efficacy and cell viability still need to be identified. Furthermore, technical complexity often limits in vivo experimentation, while challenging industrial and clinical translation. This review highlights the applications of protein transfection technologies, and then critically discuss the current methodologies and their limitations. Physical membrane perforation systems are compared to systems exploiting cellular endocytosis. Research evidence of the existence of either extracellular vesicles (EVs) or cell-penetrating peptides (CPPs)- based systems, that circumvent the endosomal systems is critically analysed. Commercial systems, novel solid-phase reverse protein transfection systems, and engineered living intracellular bacteria-based mechanisms are finally described. This review ultimately aims at finding new methodologies and possible applications of protein transfection systems, while helping the development of an evidence-based research approach.

Polymer-Based Nanostructures for Pancreatic Beta-Cell Imaging and Non-Invasive Treatment of Diabetes

Diabetes poses major economic, social, and public health challenges in all countries worldwide. Besides cardiovascular disease and microangiopathy, diabetes is a leading cause of foot ulcers and lower limb amputations. With the continued rise of diabetes prevalence, it is expected that the future burden of diabetes complications, early mortality, and disabilities will increase. The diabetes epidemic is partly caused by the current lack of clinical imaging diagnostic tools, the timely monitoring of insulin secretion and insulin-expressing cell mass (beta (β)-cells), and the lack of patients' adherence to treatment, because some drugs are not tolerated or invasively administrated. In addition to this, there is a lack of efficient topical treatment capable of stopping the progression of disabilities, in particular for treating foot ulcers. In this context, polymer-based nanostructures garnered significant interest due to their tunable physicochemical characteristics, rich diversity, and biocompatibility. This review article emphasizes the last advances and discusses the prospects in the use of polymeric materials as nanocarriers for β-cell imaging and non-invasive drug delivery of insulin and antidiabetic drugs in the management of blood glucose and foot ulcers.

Photothermal Nanomaterial-Mediated Photoporation

ConspectusDelivering biological effector molecules in cultured cells is of fundamental importance to any study or application in which the modulation of gene expression is required. Examples range from generating engineered cell lines for studying gene function to the engineering of cells for cell-based therapies such as CAR-T cells and gene-corrected stem cells for regenerative medicine. It remains a great challenge, however, to deliver biological effector molecules across the cell membrane with minimal adverse effects on cell viability and functionality. While viral vectors have been frequently used to introduce foreign nucleic acids into cells, their use is associated with safety concerns such as immunogenicity, high manufacturing cost, and limited cargo capacity.For photoporation, depending on the laser energy, membrane permeabilization happens either by local heating or by laser-induced water vapor nanobubbles (VNB). In our first study on this topic, we demonstrated that the physical force exerted by suddenly formed VNB leads to more efficient intracellular delivery as compared to mere heating. Next, we explored the use of different photothermal nanomaterials, finding that graphene quantum dots display enhanced thermal stability compared to the more traditionally used gold nanoparticles, hence providing the possibility to increase the delivery efficiency by repeated laser activation. To enable its use for the production of engineered therapeutic cells, it would be better if contact with cells with nondegradable nanoparticles is avoided as it poses toxicity and regulatory concerns. Therefore, we recently demonstrated that photoporation can be performed with biodegradable polydopamine nanoparticles as well. Alternatively, we demonstrated that nanoparticle contact can be avoided by embedding the photothermal nanoparticles in a substrate made from biocompatible electrospun nanofibers. With this variety of photoporation approaches, over the years we demonstrated the successful delivery of a broad variety of biologics (mRNA, siRNA, Cas9 ribonucleoproteins, nanobodies, etc.) in many different cell types, including hard-to-transfect cells such as T cells, embryonic stem cells, neurons, and macrophages.In this Account, we will first start with a brief introduction of the general concept and a historical development of photoporation. In the next two sections, we will extensively discuss the various types of photothermal nanomaterials which have been used for photoporation. We discriminate two types of photothermal nanomaterials: single nanostructures and composite nanostructures. The first one includes examples such as gold nanoparticles, graphene quantum dots, and polydopamine nanoparticles. The second type includes polymeric films and nanofibers containing photothermal nanoparticles as well as composite nanoscale biolistic nanostructures. A thorough discussion will be given for each type of photothermal nanomaterial, from its synthesis and characterization to its application in photoporation, with its advantages and disadvantages. In the final section, we will provide an overall discussion and elaborate on future perspectives.

Response Surface Methodology to Efficiently Optimize Intracellular Delivery by Photoporation

Photoporation is an up-and-coming technology for the gentle and efficient transfection of cells. Inherent to the application of photoporation is the optimization of several process parameters, such as laser fluence and sensitizing particle concentration, which is typically done one factor at a time (OFAT). However, this approach is tedious and runs the risk of missing a global optimum. Therefore, in this study, we explored whether response surface methodology (RSM) would allow for more efficient optimization of the photoporation procedure. As a case study, FITC-dextran molecules of 500 kDa were delivered to RAW264.7 mouse macrophage-like cells, making use of polydopamine nanoparticles (PDNPs) as photoporation sensitizers. Parameters that were varied to obtain an optimal delivery yield were PDNP size, PDNP concentration and laser fluence. Two established RSM designs were compared: the central composite design and the Box-Behnken design. Model fitting was followed by statistical assessment, validation, and response surface analysis. Both designs successfully identified a delivery yield optimum five- to eight-fold more efficiently than when using OFAT methodology while revealing a strong dependence on PDNP size within the design space. In conclusion, RSM proves to be a valuable approach to efficiently optimize photoporation conditions for a particular cell type.

Delivery of macromolecules in unstimulated T cells by photoporation with polydopamine nanoparticles

Ex vivo modification of T cells with exogenous cargo is a common prerequisite for the development of T cell therapies, such as chimeric antigen receptor therapy. Despite the clinical success and FDA approval of several such products, T cell manufacturing presents unique challenges related to therapeutic efficacy after adoptive cell transfer and several drawbacks of viral transduction-based manufacturing, such as high cost and safety concerns. To generate cellular products with optimal potency, engraftment potential and persistence in vivo, recent studies have shown that minimally differentiated T cell phenotypes are preferred. However, genetic engineering of quiescent T cells remains challenging. Photoporation is an upcoming alternative non-viral transfection method which makes use of photothermal nanoparticles, such as polydopamine nanoparticles (PDNPs), to induce transient membrane permeabilization by distinct photothermal effects upon laser irradiation, allowing exogenous molecules to enter cells. In this study, we analyzed the capability of PDNP-photoporation to deliver large model macromolecules (FITC-dextran 500 kDa, FD500) in unstimulated and expanded human T cells. We compared different sizes of PDNPs (150, 250 and 400 nm), concentrations of PDNPs and laser fluences and found an optimal condition that generated high delivery yields of FD500 in both T cell phenotypes. A multiparametric analysis of cell proliferation, surface activation markers and cytokine production, revealed that unstimulated T cells photoporated with 150 nm and 250 nm PDNPs retained their propensity to become activated, whereas those photoporated with 400 nm PDNPs did less. Our findings show that PDNP-photoporation is a promising strategy for transfection of quiescent T cells, but that PDNPs should be small enough to avoid excessive cell damage.

Nanomaterial-mediated photoporation for intracellular delivery

Translocation of extrinsic molecules into living cells is becoming increasingly crucial in biological studies ranging from cell engineering to biomedical applications. The concerns regarding biosafety and immunogenicity for conventional vectors and physical methods yet challenge effective intracellular delivery. Here, we begin with an overview of approaches for trans-membrane delivery up to now. These methods are featured with a relatively mature application but usually encounter low cell survival. Our review then proposes an advanced application for nanomaterial-sensitized photoporation triggered with a laser. We cover the mechanisms, procedures, and outcomes of photoporation-induced intracellular delivery with a highlight on its versatility to different living cells. We hope the review discussed here encourages researchers to further improvement and applications for photoporation-induced intracellular delivery. STATEMENT OF SIGNIFICANCE.

ICG-mediated photodisruption of the inner limiting membrane enhances retinal drug delivery

Many groundbreaking therapies for the treatment of blindness require delivery of biologics or cells to the inner retina by intravitreal injection. Unfortunately, the advancement of these therapies is greatly hampered by delivery difficulties where obstruction of the therapeutics at the inner limiting membrane (ILM) represents the dominant bottleneck. In this proof-of-principle study, we explore an innovative light-based approach to locally ablate the ILM in a minimally invasive and highly controlled manner, thus making the ILM more permeable for therapeutics. More specifically, we demonstrate that pulsed laser irradiation of ILM-bound indocyanine green (ICG), a clinically applied ILM dye, results in the formation of vapor nanobubbles which can disrupt the bovine ILM as well as the extraordinary thick human ILM. We have observed that this photodisruption allows for highly successful retinal delivery of model nanoparticles which are otherwise blocked by the intact ILM. Strikingly, this treatment is furthermore able of enhancing the efficacy of mRNA-loaded lipid nanoparticles within the bovine retina by a factor of 5. In conclusion, this study provides evidence for a light-based approach to overcome the ILM which has the potential to improve the efficacy of all retinal therapies hampered by this delivery barrier.

Laser-induced nanobubbles safely ablate vitreous opacities in vivo

In myopia, diabetes and ageing, fibrous vitreous liquefaction and degeneration is associated with the formation of opacities inside the vitreous body that cast shadows on the retina, appearing as 'floaters' to the patient. Vitreous opacities degrade contrast sensitivity function and can cause notable impairment in vision-related quality of life. Here we introduce 'nanobubble ablation' for safe destruction of vitreous opacities. Following intravitreal injection, hyaluronic acid-coated gold nanoparticles and indocyanine green, which is widely used as a dye in vitreoretinal surgery, spontaneously accumulate on collagenous vitreous opacities in the eyes of rabbits. Applying nanosecond laser pulses generates vapour nanobubbles that mechanically destroy the opacities in rabbit eyes and in patient specimens. Nanobubble ablation might offer a safe and efficient treatment to millions of patients suffering from debilitating vitreous opacities and paves the way for a highly safe use of pulsed lasers in the posterior segment of the eye.

Detection of aflatoxin B1 with a new label-free fluorescence aptasensor based on PVP-coated single-walled carbon nanohorns and SYBR Gold

This paper describes a novel fluorescence label-free aptasensor to detect aflatoxin B₁ (AFB₁) by utilizing SYBR Gold, aptamer, and single-walled carbon nanohorns (SWCNHs). In the presence of AFB₁, the conformation of AFB₁-specific aptamer went through and the spatial structure of this specific aptamer was transformed accordingly. Due to the resistance of the transformed aptamer when adsorbed on the surface of SWCNHs, the protection of the fluorescence of SYBR Gold was accomplished. Consequently, concentrations of AFB₁ showed a strong association with fluorescence intensity. The detection limit (LOD) of AFB₁ was 1.89 ng/mL, while the linear range was 5-200 ng/mL and fluorescence intensity satisfactorily correlated (R² = 0.9919) with the logarithm of AFB₁ concentration.

The cellular response to plasma membrane disruption for nanomaterial delivery

Delivery of nanomaterials into cells is of interest for fundamental cell biological research as well as for therapeutic and diagnostic purposes. One way of doing so is by physically disrupting the plasma membrane (PM). Several methods that exploit electrical, mechanical or optical cues have been conceived to temporarily disrupt the PM for intracellular delivery, with variable effects on cell viability. However, apart from acute cytotoxicity, subtler effects on cell physiology may occur as well. Their nature and timing vary with the severity of the insult and the efficiency of repair, but some may provoke permanent phenotypic alterations. With the growing palette of nanoscale delivery methods and applications, comes a need for an in-depth understanding of this cellular response. In this review, we summarize current knowledge about the chronology of cellular events that take place upon PM injury inflicted by different delivery methods. We also elaborate on their significance for cell homeostasis and cell fate. Based on the crucial nodes that govern cell fitness and functionality, we give directions for fine-tuning nano-delivery conditions.

Site-Specific Fluorescent Labeling, Single-Step Immunocytochemistry, and Delivery of Nanobodies into Living Cells

The smallest natural antibody fragments currently available are single-domain antibodies obtained from camelid species and sharks (variable new antigen receptors). These molecules consist of a single amino acid chain of ~120 amino acids that adopts a typical immunoglobulin fold. Single-domain antibodies (nanobodies) are monovalent and can be isolated from immunized animals, from naïve libraries, or from synthetic libraries. Importantly, their complete DNA sequences are readily obtained by default, which greatly facilitates their rapid manipulation for various applications. Here, a PCR-based protocol for inserting a sortase A recognition sequence at the carboxy-terminus of a nanobody is described. Subsequently, a sortase A-catalyzed biochemical reaction results in tagging of the nanobody with a short carboxy-terminal amino acid sequence that carries a non-canonical residue (propargyl glycine). This allows click chemistry to be performed with an azido-derivatized fluorophore, with the ensuing fluorescent nanobody being covalently and site-specifically labeled. The labeled nanobody can be used directly for immunocytochemistry, omitting the classical secondary antibody step. Also described are methods for delivery of fluorescent nanobodies into the cytoplasm of mammalian cells by photoporation, a very low-toxicity approach involving laser light and graphene quantum dots. The combined protocol embodies a novel route for studying protein function in living cells at high resolution.

Plasma membrane perforation by GSDME during apoptosis-driven secondary necrosis

Secondary necrosis has long been perceived as an uncontrolled process resulting in total lysis of the apoptotic cell. Recently, it was shown that progression of apoptosis to secondary necrosis is regulated by Gasdermin E (GSDME), which requires activation by caspase-3. Although the contribution of GSDME in this context has been attributed to its pore-forming capacity, little is known about the kinetics and size characteristics of this. Here we report on the membrane permeabilizing features of GSDME by monitoring the influx and efflux of dextrans of different sizes into/from anti-Fas-treated L929sAhFas cells undergoing apoptosis-driven secondary necrosis. We found that GSDME accelerates cell lysis measured by SYTOX Blue staining but does not affect the exposure of phosphatidylserine on the plasma membrane. Furthermore, loss of GSDME expression clearly hampered the influx of fluorescently labeled dextrans while the efflux happened independently of the presence or absence of GSDME expression. Importantly, both in- and efflux of dextrans were dependent on their molecular weight. Altogether, our results demonstrate that GSDME regulates the passage of compounds together with other plasma membrane destabilizing subroutines.

Photothermal nanofibres enable safe engineering of therapeutic cells

Nanoparticle-sensitized photoporation is an upcoming approach for the intracellular delivery of biologics, combining high efficiency and throughput with excellent cell viability. However, as it relies on close contact between nanoparticles and cells, its translation towards clinical applications is hampered by safety and regulatory concerns. Here we show that light-sensitive iron oxide nanoparticles embedded in biocompatible electrospun nanofibres induce membrane permeabilization by photothermal effects without direct cellular contact with the nanoparticles. The photothermal nanofibres have been successfully used to deliver effector molecules, including CRISPR-Cas9 ribonucleoprotein complexes and short interfering RNA, to adherent and suspension cells, including embryonic stem cells and hard-to-transfect T cells, without affecting cell proliferation or phenotype. In vivo experiments furthermore demonstrated successful tumour regression in mice treated with chimeric antibody receptor T cells in which the expression of programmed cell death protein 1 (PD1) is downregulated after nanofibre photoporation with short interfering RNA to PD1. In conclusion, cell membrane permeabilization with photothermal nanofibres is a promising concept towards the safe and more efficient production of engineered cells for therapeutic applications, including stem cell or adoptive T cell therapy.

Simultaneous Detection of Viability and Concentration of Microalgae Cells Based on Chlorophyll Fluorescence and Bright Field Dual Imaging

Ship ballast water contains high concentration of plankton, bacteria, and other microorganisms. If the huge amount of ballast water is discharged without being inactivated, it will definitely spell disaster to the marine environment. Microalgae is the most common species exiting in ballast water, so the detection of the concentration and viability of microalgae is a very important issue. The traditional methods of detecting microalgae in ballast water were costly and need the help of bulky equipment. Herein, a novel method based on microalgae cell intracellular chlorophyll fluorescence (CF) imaging combines with cell bright field (BF) microscopy was proposed. The geometric features of microalgae cells were obtained by BF image, and the cell viability was obtained by CF image. The two images were fused through the classic image registration algorithm to achieve simultaneous detection of the viability and concentration of microalgae cells. Furthermore, a low-cost, miniaturized CF/BF microscopy imaging prototype system based on the above principles was designed. In order to verify the effectiveness of the proposed method, four typical microalgae in ballast water (Platymonas, Pyramimonas sp., Chrysophyta, and Prorocentrum lima) were selected as the samples. The experimental results show that the self-developed prototype can quickly and accurately determine the concentration and the viability of microalgae cells in ship ballast water based on the dual images of BF and CF, and the detection accuracy is equivalent to that of commercial microscope. It was the first time to simultaneously detect the viability and concentration of microalgae cells in ship ballast water using the method that combining the fluorescence and bright field images; moreover, a miniaturized microscopic imaging prototype was developed. Those findings expected to contribute to the microalgae detection and ship ballast water management.

Bubble Forming Films for Spatial Selective Cell Killing

Photodynamic and photothermal cell killing at the surface of tissues finds applications in medicine. However, a lack of control over heat dissipation following a treatment with light might damage surrounding tissues. A new strategy to kill cells at the surface of tissues is reported. Polymeric films are designed in which iron oxide nanoparticles are embedded as photosensitizers. Irradiation of the films with pulsed laser light generates water vapor bubbles at the surface of the films. It is found that "bubble-films" can kill cells in close proximity to the films due to mechanical forces which arise when the bubbles collapse. Local irradiation of bubble-films allows for spatial selective single cell killing. As nanosurgery becomes attractive in ophthalmology to remove superficial tumors, bubble-films are applied on the cornea and it is found that irradiation of the bubble-films allows spatial and selective killing of corneal cells. As i) the photosensitizer is embedded in the films, which reduces its uptake by cells and spreading into tissues and ii) the bubble-films can be removed from the tissue after laser treatment, while iii) a low laser fluence is sufficient to generate vapor bubbles, it is foreseen that bubble-films might become promising for safe resection of superficial tumors.

Diluted-CdS Quantum Dot-Assisted SnO2 Electron Transport Layer with Excellent Conductivity and Suitable Band Alignment for High-Performance Planar Perovskite Solar Cells

An electron transport layer (ETL) with excellent conductivity and suitable band alignment plays a key role in accelerating charge extraction and transfer for achieving highly efficient planar perovskite solar cells (PSCs). Herein, a novel diluted-cadmium sulfide quantum dot (CdS QD)-assisted SnO₂ ETL has been developed with a low-temperature fabrication process. The slight addition of CdS QDs first enhances the crystallinity and flatness of SnO₂ ETLs so that it provides a promising workstation to obtain high-quality perovskite absorption layers. It also amazingly increases the conductivity of the SnO₂ ETL by an order of magnitude and regulates the energy level matching between the SnO₂ ETL and perovskite. These outstanding properties greatly accelerate the charge extraction and transfer. Thus, the MAPbI₃-based PSCs with such a diluted-CdSQD-assisted SnO₂ ETL achieve a maximum power conversion efficiency of 20.78% and obtain a better stability of devices in air. These findings testify the importance and potential of semiconductor QD modification on ETLs, which may pave the way for developing such composite ETLs for further enhancing photovoltaic performance of planar PSCs.

Computational Studies on the Materials Combining Graphene Quantum Dots and Pt Complexes with Adjustable Luminescence Characteristics

Graphene materials with particular properties are proved to be beneficial to photoelectric devices, but there are rare reports on a positive effect by graphene on emissive layer materials of organic light-emitting diodes (OLEDs) previously. On the basis of the latest important experiments, an OLED device with the aid of graphene quantum dots shows the dawn of their application for luminescent materials. The luminescence performance has been improved, but the understanding of the internal excited-state radiation mechanism of the material needs further study. In this work, the Pt(II)-coordinated graphene quantum dot coplanar structures with different shapes are studied theoretically in detail, and the results present the improvement in phosphorescence under the promoted radiative decay and suppressed nonradiative decay. This composite combines the advantages of transition metal complexes and graphene quantum dots and also exhibits excellent properties in the light absorption region and carrier transportation for the OLED. This comprehensive theoretical calculation research can provide a comprehensive basis of the material design in the future.

An Inside Job: Applications of Intracellular Single Domain Antibodies

Sera of camelid species contain a special kind of antibody that consists only of heavy chains. The variable antigen binding domain of these heavy chain antibodies can be expressed as a separate entity, called a single domain antibody that is characterized by its small size, high solubility and oftentimes exceptional stability. Because of this, most single domain antibodies fold correctly when expressed in the reducing environment of the cytoplasm, and thereby retain their antigen binding specificity. Single domain antibodies can thus be used to target a broad range of intracellular proteins. Such intracellular single domain antibodies are also known as intrabodies, and have proven to be highly useful tools for basic research by allowing visualization, disruption and even targeted degradation of intracellular proteins. Furthermore, intrabodies can be used to uncover prospective new therapeutic targets and have the potential to be applied in therapeutic settings in the future. In this review we provide a brief overview of recent advances in the field of intracellular single domain antibodies, focusing on their use as research tools and potential therapeutic applications. Special attention is given to the available methods that allow delivery of single domain antibodies into cells.

Transforming nanobodies into high-precision tools for protein function analysis

Single-domain antibodies, derived from camelid heavy antibodies (nanobodies) or shark variable new antigen receptors, have attracted increasing attention in recent years due to their extremely versatile nature and the opportunities they offer for downstream modification. Discovered more than three decades ago, these 120-amino acid (∼15-kDa) antibody fragments are known to bind their target with high specificity and affinity. Key features of nanobodies that make them very attractive include their single-domain nature, small size, and affordable high-level expression in prokaryotes, and their cDNAs are routinely obtained in the process of their isolation. This facilitates and stimulates new experimental approaches. Hence, it allows researchers to formulate new answers to complex biomedical questions. Through elementary PCR-based technologies and chemical modification strategies, their primary structure can be altered almost at leisure while retaining their specificity and biological activity, transforming them into highly tailored tools that meet the increasing demands of current-day biomedical research. In this review, various aspects of camelid nanobodies are expounded, including intracellular delivery in recombinant format for manipulation of, i.e., cytoplasmic targets, their derivatization to improve nanobody orientation as a capturing device, approaches to reversibly bind their target, their potential as protein-silencing devices in cells, the development of strategies to transfer nanobodies through the blood-brain barrier and their application in CAR-T experimentation. We also discuss some of their disadvantages and conclude with future prospects.

Intracellular Delivery of mRNA in Adherent and Suspension Cells by Vapor Nanobubble Photoporation

Efficient and safe cell engineering by transfection of nucleic acids remains one of the long-standing hurdles for fundamental biomedical research and many new therapeutic applications, such as CAR T cell-based therapies. mRNA has recently gained increasing attention as a more safe and versatile alternative tool over viral- or DNA transposon-based approaches for the generation of adoptive T cells. However, limitations associated with existing nonviral mRNA delivery approaches hamper progress on genetic engineering of these hard-to-transfect immune cells. In this study, we demonstrate that gold nanoparticle-mediated vapor nanobubble (VNB) photoporation is a promising upcoming physical transfection method capable of delivering mRNA in both adherent and suspension cells. Initial transfection experiments on HeLa cells showed the importance of transfection buffer and cargo concentration, while the technology was furthermore shown to be effective for mRNA delivery in Jurkat T cells with transfection efficiencies up to 45%. Importantly, compared to electroporation, which is the reference technology for nonviral transfection of T cells, a fivefold increase in the number of transfected viable Jurkat T cells was observed. Altogether, our results point toward the use of VNB photoporation as a more gentle and efficient technology for intracellular mRNA delivery in adherent and suspension cells, with promising potential for the future engineering of cells in therapeutic and fundamental research applications.

Biocompatible nitrogen-doped carbon dots: synthesis, characterization, and application

Carbon dots (CDs) are promising materials for biomedical applications owing to their unique properties, biocompatibility, and biodegradability. The current studies on CDs are focused on improving their functionality by modulating their electronic structure, which helps in controlling their chemical, optical, and electrical properties. Doping with heteroatoms is a typical approach for modulating the electronic structure of CDs. In particular, there has been considerable progress in nitrogen-doped CDs for improving their potential for various biomedical applications, including optical imaging, drug delivery, and light-mediated imaging/therapeutic applications such as photoacoustic imaging, photothermal therapy, and photodynamic therapy. In this review, the important features of nitrogen-doped CDs are discussed along with the recent studies on these materials and their prospects.

Applying Antibodies Inside Cells: Principles and Recent Advances in Neurobiology, Virology and Oncology

To interfere with cell function, many scientists rely on methods that target DNA or RNA due to the ease with which they can be applied. Proteins are usually the final executors of function but are targeted only indirectly by these methods. Recent advances in targeted degradation of proteins based on proteolysis-targeting chimaeras (PROTACs), ubiquibodies, deGradFP (degrade Green Fluorescent Protein) and other approaches have demonstrated the potential of interfering directly at the protein level for research and therapy. Proteins can be targeted directly and very specifically by antibodies, but using antibodies inside cells has so far been considered to be challenging. However, it is possible to deliver antibodies or other proteins into the cytosol using standard laboratory equipment. Physical methods such as electroporation have been demonstrated to be efficient and validated thoroughly over time. The expression of intracellular antibodies (intrabodies) inside cells is another way to interfere with intracellular targets at the protein level. Methodological strategies to target the inside of cells with antibodies, including delivered antibodies and expressed antibodies, as well as applications in the research areas of neurobiology, viral infections and oncology, are reviewed here. Antibodies have already been used to interfere with a wide range of intracellular targets. Disease-related targets included proteins associated with neurodegenerative diseases such as Parkinson's disease (α-synuclein), Alzheimer's disease (amyloid-β) or Huntington's disease (mutant huntingtin [mHtt]). The applications of intrabodies in the context of viral infections include targeting proteins associated with HIV (e.g. HIV1-TAT, Rev, Vif, gp41, gp120, gp160) and different oncoviruses such as human papillomavirus (HPV), hepatitis B virus (HBV), hepatitis C virus (HCV) and Epstein-Barr virus, and they have been used to interfere with various targets related to different processes in cancer, including oncogenic pathways, proliferation, cell cycle, apoptosis, metastasis, angiogenesis or neo-antigens (e.g. p53, human epidermal growth factor receptor-2 [HER2], signal transducer and activator of transcription 3 [STAT3], RAS-related RHO-GTPase B (RHOB), cortactin, vascular endothelial growth factor receptor 2 [VEGFR2], Ras, Bcr-Abl). Interfering at the protein level allows questions to be addressed that may remain unanswered using alternative methods. This review addresses why direct targeting of proteins allows unique insights, what is currently feasible in vitro, and how this relates to potential therapeutic applications.

Nanobody click chemistry for convenient site-specific fluorescent labelling, single step immunocytochemistry and delivery into living cells by photoporation and live cell imaging

While conventional antibodies have been an instrument of choice in immunocytochemistry for some time, their small counterparts known as nanobodies have been much less frequently used for this purpose. In this study we took advantage of the availability of nanobody cDNAs to site-specifically introduce a non-standard amino acid carrying an azide/alkyne moiety, allowing subsequent Cu(I)-catalyzed Azide-Alkyne Click Chemistry (CuAAC). This generated a fluorescently labelled nanobody that can be used in single step immunocytochemistry as compared to conventional two step immunocytochemistry. Two strategies were explored to label nanobodies with Alexa Fluor 488. The first involved enzymatic addition of an alkyne-containing peptide to nanobodies using sortase A, while the second consisted of incorporating para-azido phenylalanine at the nanobody C-terminus. Through these approaches, the fluorophore was covalently and site-specifically attached. It was demonstrated that cortactin and β-catenin, cytoskeletal and adherens junction proteins respectively, can be imaged in cells in this manner through single step immunocytochemistry. However, fixation and permeabilization of cells can alter native protein structure and form a dense cross-linked protein network, encumbering antibody binding. It was shown that photoporation prior to fixation not only allowed delivery of nanobodies into living cells, but also facilitated β-catenin nanobody Nb86 imaging of its target, which was not possible in fixed cells. Pharmacological inhibitors are lacking for many non-enzymatic proteins, and it is therefore expected that new biological information will be obtained through photoporation of fluorescent nanobodies, which allows the study of short term effects, independent of gene-dependent (intrabody) expression.

Intracellular Labeling with Extrinsic Probes: Delivery Strategies and Applications

Extrinsic probes have outstanding properties for intracellular labeling to visualize dynamic processes in and of living cells, both in vitro and in vivo. Since extrinsic probes are in many cases cell-impermeable, different biochemical, and physical approaches have been used to break the cell membrane barrier for direct delivery into the cytoplasm. In this Review, these intracellular delivery strategies are discussed, briefly explaining the mechanisms and how they are used for live-cell labeling applications. Methods that are discussed include three biochemical agents that are used for this purpose-purpose-different nanocarriers, cell penetrating peptides and the pore-foraming bacterial toxin streptolysin O. Most successful intracellular label delivery methods are, however, based on physical principles to permeabilize the membrane and include electroporation, laser-induced photoporation, micro- and nanoinjection, nanoneedles or nanostraws, microfluidics, and nanomachines. The strengths and weaknesses of each strategy are discussed with a systematic comparison provided. Finally, the extrinsic probes that are reported for intracellular labeling so-far are summarized, together with the delivery strategies that are used and their performance. This combined information should provide for a useful guide for choosing the most suitable delivery method for the desired probes.

Expanding the substrate selectivity of SNAP/CLIP-tagging of intracellular targets

SNAP-tag belongs to a class of genetic tools of protein labeling that complements fluorescent proteins. This single-turnover enzyme is a mutant of human DNA repair protein O⁶-alkylguanine-DNA alkyltransferase (hAGT). It accepts, in most cases, label-carrying O⁶-benzylguanines or benzyl-2-chloro-6-aminopyrimidines as suitable substrates. In this article, strategies and methods to expand the scope of the labels for intracellular proteins of live cells via the actions of SNAP-tag are presented. CLIP-tag is another mutant of the hAGT that was engineered to have mutually exclusive substrate specificity from SNAP-tag. The use of complementary bioorthogonal chemical reactions in conjunction with orthogonal enzymatic SNAP/CLIP-tags for the purpose of dual-color intracellular labeling is also described.

Developed a novel quinazolinone based turn-on fluorescence probe for highly selective monitoring hypochlorite and its bioimaging applications

A novel quinazolinone based turn-on fluorescence probe for sensitive monitoring hypochlorite was prepared using the mild condensation reaction between 2-(2'-hydroxyphenyl)-4(3H)-quinazolinone derivative and 4-methylbenzenesulfonyl hydrazide. The probe exhibited specific selectivity to ClO^- with obvious optical signal changes from weak fluorescence at 560 nm to a strong fluorescence emission at 520 nm and color changes from colorless to yellow, which could be noticed by the naked eye. The detection limit toward hypochlorite is as low as 11.4 nM. Moreover, the probe could sensitively response to ClO^- in living cells with satisfying imaging effect and has been successfully applied to the determination of ClO^- in practical water samples, which indicated that the probe has certain application potential for hypochlorite monitoring.

Surface Functionalization with Polyethylene Glycol and Polyethyleneimine Improves the Performance of Graphene-Based Materials for Safe and Efficient Intracellular Delivery by Laser-Induced Photoporation

Nanoparticle mediated laser-induced photoporation is a physical cell membrane disruption approach to directly deliver extrinsic molecules into living cells, which is particularly promising in applications for both adherent and suspension cells. In this work, we explored surface modifications of graphene quantum dots (GQD) and reduced graphene oxide (rGO) with polyethylene glycol (PEG) and polyethyleneimine (PEI) to enhance colloidal stability while retaining photoporation functionality. After photoporation with FITC-dextran 10 kDa (FD10), the percentage of positive HeLa cells (81% for GQD-PEG, 74% for rGO-PEG and 90% for rGO-PEI) increased approximately two-fold compared to the bare nanomaterials. While for Jurkat suspension cells, the photoporation efficiency with polymer-modified graphene-based nanomaterial reached as high as 80%. Cell viability was >80% in all these cases. In addition, polymer functionalization proved to be beneficial for the delivery of larger macromolecules (FD70 and FD500) as well. Finally, we show that rGO is suitable for photoporation using a near-infrared laser to reach 80% FD10 positive HeLa cells at 80% cell viability. We conclude that modification of graphene-based nanoparticles with PEG and especially PEI provide better colloidal stability in cell medium, resulting in more uniform transfection and overall increased efficiency.

Long-term live-cell microscopy with labeled nanobodies delivered by laser-induced photoporation

Fluorescence microscopy is the method of choice for studying intracellular dynamics. However, its success depends on the availability of specific and stable markers. A prominent example of markers that are rapidly gaining interest are nanobodies (Nbs, ~ 15 kDa), which can be functionalized with bright and photostable organic fluorophores. Due to their relatively small size and high specificity, Nbs offer great potential for high-quality long-term subcellular imaging, but suffer from the fact that they cannot spontaneously cross the plasma membrane of live cells. We have recently discovered that laser-induced photoporation is well suited to deliver extrinsic labels to living cells without compromising their viability. Being a laser-based technology, it is readily compatible with light microscopy and the typical cell recipients used for that. Spurred by these promising initial results, we demonstrate here for the first time successful long-term imaging of specific subcellular structures with labeled nanobodies in living cells. We illustrate this using Nbs that target GFP/YFP-protein constructs accessible in the cytoplasm, actin-bundling protein Fascin, and the histone H2A/H2B heterodimers. With an efficiency of more than 80% labeled cells and minimal toxicity (~ 2%), photoporation proved to be an excellent intracellular delivery method for Nbs. Time-lapse microscopy revealed that cell division rate and migration remained unaffected, confirming excellent cell viability and functionality. We conclude that laser-induced photoporation labeled Nbs can be easily delivered into living cells, laying the foundation for further development of a broad range of Nbs with intracellular targets as a toolbox for long-term live-cell microscopy.

Delivery of Mixed-Lineage Kinase Domain-Like Protein by Vapor Nanobubble Photoporation Induces Necroptotic-Like Cell Death in Tumor Cells

Modern molecular medicine demands techniques to efficiently deliver molecules directly into mammalian cells. As proteins are the final mediators of most cellular pathways, efficient intracellular protein delivery techniques are highly desired. In this respect, photoporation is a promising recent technique for the delivery of proteins directly into living cells. Here, we show the possibility to deliver a model saccharide (FD70) and a model protein (FITC-BSA) into murine B16 melanoma cells by using the vapor nanobubble photoporation technique with an efficiency of 62% and 38%, respectively. Next, we delivered the mixed-lineage kinase domain-like (MLKL) protein, the most terminal mediator of necroptosis currently known, and caspase-8 and -3 protein, which are important proteins in the initiation and execution of apoptosis. A significant drop in cell viability with 62%, 71% and 64% cell survival for MLKL, caspase-8 and caspase-3, respectively, was observed. Remarkably, maximal cell death induction was already observed within 1 h after protein delivery. Transduction of purified recombinant MLKL by photoporation resulted in rapid cell death characterized by cell swelling and cell membrane rupture, both hallmarks of necroptosis. As necroptosis has been identified as a type of cell death with immunogenic properties, this is of interest to anti-cancer immunotherapy. On the other hand, transduction of purified recombinant active caspase-3 or -8 into the tumor cells resulted in rapid cell death preceded by membrane blebbing, which is typical for apoptosis. Our results suggest that the type of cell death of tumor cells can be controlled by direct transduction of effector proteins that are involved in the executioner phase of apoptosis or necroptosis.

Deep-Ultraviolet Emissive Carbon Nanodots

Deep-ultraviolet (DUV) emissive carbon nanodots (CNDs) have been designed theoretically and demonstrated experimentally based on the results of first-principles calculations using the density functional theory method. The emission of the CNDs is located in the range from 280 to 300 nm, which coincides well with the results of theoretical calculation results. The photoluminescence (PL) quantum yield (QY) of the CNDs is up to 31.6%, and the strong emission of the CNDs originates from core-state (π-π*) carriers' radiative recombination and surface passivation. Benefiting from the core-state emission and surface group passivation, the emission of the CNDs is independent of the excitation wavelength and ambient solvent. DUV light-emitting diodes (LEDs) have been fabricated based on the DUV emissive CNDs, and the LEDs can be used as the excitation source to excite blue, green, and red CNDs, indicating their potential application in DUV light sources. This work may provide a clue for the designing and realizing of DUV emissive CNDs, thus promising the potential application of CNDs in DUV light-emitting sources.

Multimorphological top-hat-based multiscale target classification algorithm for real-time image processing

The traditional top-hat method is a commonly used method that quickly separates targets from a background. It is used for its fast processing speed and wide range of applications on programmable hardware. However, in some important fields such as microfluidic control, medicine, aerospace, and optical measurement, the observed targets are often spotted with different sizes. The formation mechanism of multiscale spots varies from each other so that they can not be successfully extracted and classified by the traditional top-hat method. To ensure the integrity of targets with a specific size and suppressed noise, the imaging mechanism of different types of spots are studied, and an improved top-hat method with a gray-scale value-based transform is proposed. Compared with the traditional top-hat method, the proposed algorithm is more effective in completely removing unwanted spots. The calculated results of the simulated and real images verify the effectiveness of the double top-hat method in extracting targets with a specific size. Additionally, the resolution of this method is up to the parameter k, which has been discussed in this paper. Furthermore, a multi-top-hat algorithm is presented to distinguish spots of different sizes, and it could be used for real-time multiscale target detection and tracking, as well as real-time multiscale target detection and tracking.

Photoablation of Human Vitreous Opacities by Light-Induced Vapor Nanobubbles

Myopia, diabetes, and aging are the main causes of progressive vitreous collagen aggregation, resulting in vitreous opacities, which can significantly disturb vision. As vitreous opacities, which induce the visual phenomenon of "floaters", are accessible with nanomaterials and light, we propose a nanotechnology-based approach to locally ablate them with highly reduced light energy compared to the more traditional YAG laser therapy. Our strategy relies on the plasmon properties of gold nanoparticles that generate vapor nanobubbles upon pulsed-laser illumination whose mechanical force can ablate vitreous opacities. We designed gold nanoparticles coated with hyaluronic acid (HA), which have excellent diffusional mobility in human vitreous, an essential requirement to reach the vitreous opacities. In addition, we found that HA-coated gold nanoparticles can accumulate extensively on human vitreous opacities that were obtained by vitrectomy from patients with vision-degrading myodesopsia. When subsequently applying nanosecond laser pulses, the collagen aggregates were efficiently destroyed with ∼1000 times less light energy than typically used in YAG laser therapy. This low-energy "floater-specific destruction", which is due to the accumulation of the small gold nanoparticles on the opacities, is attractive, as it may be safer to the surrounding ocular tissues while at the same time being easier and faster to apply compared to YAG laser therapy, where the opacities need to be ablated piece by piece by a tightly focused laser beam. Gold nanoparticle-assisted photoablation may therefore provide a safer, faster, and more reliable destruction of vitreous opacities in the treatment of ophthalmologic diseases.

A label-free fluorometric aptasensor for adenosine triphosphate (ATP) detection based on aggregation-induced emission probe

Based on Aggregation-Induced Emission (AIE), the development of a label-free, simple and sensitive fluorometric aptasensor for adenosine triphosphate (ATP) detection is described. With ATP present, the aptamers will combine with ATP and the conformation of the aptamer will switch from a random coil to an antiparallel G-quadruplex, which impedes the digestion by exonuclease I (Exo I). Addition of 4,4 -(1E,1E)-2,2-(anthracene-9,10-diyl) bis (ethene-2,1-diyl) bis (N,N, N-trimethyl-benzenaminium iodide) (DSAI) into the solution will cause aggregation of DSAI on the surface of the aptamer/ATP complex and consequently give rise to strong emission. Additionally, a good linear relationship was observed under optimized conditions between the fluorescence intensities and the logarithm of ATP concentrations (R² = 0.9908). The established aptamer sensor was highly sensitive and exhibited a low limit of detection of 32.8 nM, with superior specificity for ATP. It was also used in the quantification of ATP levels in human serum samples and demonstrated satisfactory recoveries in the scope of 93.2%-107.6%. The cellular ATP assay results indicated that the developed method can be used for monitoring ATP concentrations in cell extracts without the interference of other substances in the cells. This method offers several advantages such as simplicity, rapidity, low cost and excellent selectivity, which make it hold great potential for the detection of ATP in bioanalytical and biological studies.

Exploring Light-Sensitive Nanocarriers for Simultaneous Triggered Antibiotic Release and Disruption of Biofilms Upon Generation of Laser-Induced Vapor Nanobubbles

Impaired penetration of antibiotics through bacterial biofilms is one of the reasons for failure of antimicrobial therapy. Hindered drug diffusion is caused on the one hand by interactions with the sticky biofilm matrix and on the other hand by the fact that bacterial cells are organized in densely packed clusters of cells. Binding interactions with the biofilm matrix can be avoided by encapsulating the antibiotics into nanocarriers, while interfering with the integrity of the dense cell clusters can enhance drug transport deep into the biofilm. Vapor nanobubbles (VNB), generated from laser irradiated nanoparticles, are a recently reported effective way to loosen up the biofilm structure in order to enhance drug transport and efficacy. In the present study, we explored if the disruptive force of VNB can be used simultaneously to interfere with the biofilm structure and trigger antibiotic release from light-responsive nanocarriers. The antibiotic tobramycin was incorporated in two types of light-responsive nanocarriers-liposomes functionalized with gold nanoparticles (Lip-AuNP) and graphene quantum dots (GQD)-and their efficacy was evaluated on Pseudomonas aeruginosa biofilms. Even though the anti-biofilm efficacy of tobramycin was improved by liposomal encapsulation, electrostatic functionalization with 70 nm AuNP unfortunately resulted in premature leakage of tobramycin in a matter of hours. Laser-irradiation consequently did not further improve P. aeruginosa biofilm eradication. Adsorption of tobramycin to GQD, on the other hand, did result in a stable formulation with high encapsulation efficiency, without burst release of tobramycin from the nanocarriers. However, even though laser-induced VNB formation from GQD resulted in biofilm disruption, an enhanced anti-biofilm effect was not achieved due to tobramycin not being efficiently released from GQD. Even though this study was unsuccessful in designing suitable nanocarriers for simultaneous biofilm disruption and light-triggered release of tobramycin, it provides insights into the difficulties and challenges that need to be considered for future developments in this regard.

Biochemical sensing in graphene-enhanced microfiber resonators with individual molecule sensitivity and selectivity

Photonic sensors that are able to detect and track biochemical molecules offer powerful tools for information acquisition in applications ranging from environmental analysis to medical diagnosis. The ultimate aim of biochemical sensing is to achieve both quantitative sensitivity and selectivity. As atomically thick films with remarkable optoelectronic tunability, graphene and its derived materials have shown unique potential as a chemically tunable platform for sensing, thus enabling significant performance enhancement, versatile functionalization and flexible device integration. Here, we demonstrate a partially reduced graphene oxide (prGO) inner-coated and fiber-calibrated Fabry-Perot dye resonator for biochemical detection. Versatile functionalization in the prGO film enables the intracavity fluorescent resonance energy transfer (FRET) to be chemically selective in the visible band. Moreover, by measuring the intermode interference via noise canceled beat notes and locked-in heterodyne detection with Hz-level precision, we achieved individual molecule sensitivity for dopamine, nicotine and single-strand DNA detection. This work combines atomic-layer nanoscience and high-resolution optoelectronics, providing a way toward high-performance biochemical sensors and systems.