Monitoring optoporated process on mammalian cells by real-time measurement of membrane resealing time

Significance

Resealing time based loading efficiency of optoporation is the key parameter for drug or gene delivery. This work describes a comparatively simple optical approach to directly measure the cell membrane resealing time of the gold nanoparticle mediated photoporation.

Aim

To establish a membrane potential detection optical system, which can provide a direct measurement of resealing time of the optoporated cells.

Approach

Voltage sensitive dye has been used to label the gold nanoparticle covered cell before laser activation and the resealing time was estimated from the voltage change due to the fluorescence light intensity change before and after laser activation. The approach has been validated by the simulated data based on diffusion model and Monte Carlo simulation and the experimental data obtained from a flow cytometry analysis.

Results

The measured resealing time after perforation varied from 28.6 to 163.8 s on Hela cells when the irradiation fluence was increased, with a correlation coefficient (R2) of 0.9938. This result is in agreement with the resealing time (1-2 min) of photothermal porated Hela cells measured by electrical impedance method. The intracellular delivery efficiency of extracellular macromolecular under the same irradiation fluence depends mainly on diffusion velocity rather than pore size.

Conclusion

The method described here can be used to directly measure resealing time of optoporated cells for accurately estimating the loading efficiency on discovering the mechanism of optoporation.

Laser-assisted nucleic acid delivery: A systematic review

Gene therapy has become an effective treatment modality for some conditions. Laser light may augment or enhance gene therapy through photomechanical, photothermal, and photochemical. This review examined the evidence base for laser therapy to enhance nucleic acid transfection in mammalian cells. An electronic search of MEDLINE, Scopus, EMBASE, Web of Science, and Google Scholar was performed, covering all available years. The preferred reporting items for systematic reviews and meta-analyses guideline for systematic reviews was used for designing the study and analyzing the results. In total, 49 studies of laser irradiation for nucleic acid delivery were included. Key approaches were optoporation, photomechanical gene transfection, and photochemical internalization. Optoporation is better suited to cells in culture, photomechanical and photochemical approaches appear well suited to in vivo use. Additional studies explored the impact of photothermal for enhancing gene transfection. Each approach has merits and limitations. Augmenting nucleic acid delivery using laser irradiation is a promising method for improving gene therapy. Laser protocols can be non-invasive because of the penetration of desirable wavelengths of light, but it depends on various parameters such as power density, treatment duration, irradiation mode, etc. The current protocols show low efficiency, and there is a need for further work to optimize irradiation parameters.

A novel cell transfection platform based on laser optoporation mediated by Au nanostar layers

The recently developed laser-induced cell transfection mediated by Au nanoparticles is a promising alternative to the well-established lipid-based transfection or to electroporation. Optoporation is based on the laser plasmonic heating of nanoparticles located near the cell membrane. However, the uncontrollable cell damage from intense laser pulses and from random attachment of nanoparticles may be crucial for transfection. We present a novel plasmonic optoporation technique that uses Au nanostar layers immobilized in culture microplate wells. HeLa cells were grown directly on Au nanostar layers, after which they were subjected to continuous-wave 808 nm laser irradiation. An Au monolayer density ~15 μg/cm² and an absorbed energy of about 15 to 30 J were found to be optimal for optoporation. Propidium iodide molecules were used as model penetrating agent. The transfection efficiency evaluated using fluorescence microscopy for HeLa cells transfected with pGFP under optimized optoporation conditions (95% ± 5%) was similar to the efficiency of TurboFect. The technique's efficiency (295 ± 10 relative light units, RLU), demonstrated by transfecting HeLa cells with the pCMV-GLuc 2 control plasmid, was greater than that obtained by transfection of HeLa cells with the TurboFect agent (220 ± 10 RLU). The cell viability in plasmonic optoporation (92% ± 7%), too, was greater than that in transfection with TurboFect (75% ± 7%).

Advanced physical techniques for gene delivery based on membrane perforation

Gene delivery as a promising and valid tool has been used for treating many serious diseases that conventional drug therapies cannot cure. Due to the advancement of physical technology and nanotechnology, advanced physical gene delivery methods such as electroporation, magnetoporation, sonoporation and optoporation have been extensively developed and are receiving increasing attention, which have the advantages of briefness and nontoxicity. This review introduces the technique detail of membrane perforation, with a brief discussion for future development, with special emphasis on nanoparticles mediated optoporation that have developed as an new alternative transfection technique in the last two decades. In particular, the advanced physical approaches development and new technology are highlighted, which intends to stimulate rapid advancement of perforation techniques, develop new delivery strategies and accelerate application of these techniques in clinic.

Ultrafast laser-assisted spatially targeted optoporation into cortical axons and retinal cells in the eye

Visualization and assessment of the cellular structure and function require localized delivery of the molecules into specific cells in restricted spatial regions of the tissue and may necessitate subcellular delivery and localization. Earlier, we have shown ultrafast near-infrared laser beam-assisted optoporation of actin-staining molecules into cortical neurons with single-cell resolution and high efficiency. However, diffusion of optoporated molecules in soma degrades toward the growth cone, leading to difficulties in visualization of the actin network in the growth cone in cases of long axons. Here, we demonstrate optoporation of impermeable molecules to functional cortical neurons by precise laser subaxotomy near the growth cone, leading to visualization of the actin network in the growth cone. Further, we demonstrate patterned delivery of impermeable molecules into targeted retinal cells in the rat eye. The development of optoporation as a minimally invasive approach to reliably deliver exogenous molecules into targeted axons and soma of retinal neurons in vivo will enable enhanced visualization of the structure and function of the retina.

Rational Design of Plasmonic Nanoparticles for Enhanced Cavitation and Cell Perforation

Metallic nanoparticles are routinely used as nanoscale antenna capable of absorbing and converting photon energy with subwavelength resolution. Many applications, notably in nanomedicine and nanobiotechnology, benefit from the enhanced optical properties of these materials, which can be exploited to image, damage, or destroy targeted cells and subcellular structures with unprecedented precision. Modern inorganic chemistry enables the synthesis of a large library of nanoparticles with an increasing variety of shapes, composition, and optical characteristic. However, identifying and tailoring nanoparticles morphology to specific applications remains challenging and limits the development of efficient nanoplasmonic technologies. In this work, we report a strategy for the rational design of gold plasmonic nanoshells (AuNS) for the efficient ultrafast laser-based nanoscale bubble generation and cell membrane perforation, which constitute one of the most crucial challenges toward the development of effective gene therapy treatments. We design an in silico rational design framework that we use to tune AuNS morphology to simultaneously optimize for the reduction of the cavitation threshold while preserving the particle structural integrity. Our optimization procedure yields optimal AuNS that are slightly detuned compared to their plasmonic resonance conditions with an optical breakdown threshold 30% lower than randomly selected AuNS and 13% lower compared to similarly optimized gold nanoparticles (AuNP). This design strategy is validated using time-resolved bubble spectroscopy, shadowgraphy imaging and electron microscopy that confirm the particle structural integrity and a reduction of 51% of the cavitation threshold relative to optimal AuNP. Rationally designed AuNS are finally used to perforate cancer cells with an efficiency of 61%, using 33% less energy compared to AuNP, which demonstrate that our rational design framework is readily transferable to a cell environment. The methodology developed here thus provides a general strategy for the systematic design of nanoparticles for nanomedical applications and should be broadly applicable to bioimaging and cell nanosurgery.

Spatially, Temporally, and Quantitatively Controlled Delivery of Broad Range of Molecules into Selected Cells through Plasmonic Nanotubes

A Universal plasmonic/microfluidic platform for spatial and temporal controlled intracellular delivery is described. The system can inject/transfect the desired amount of molecules with an efficacy close to 100%. Moreover, it is highly scalable from single cells to large ensembles without administering the molecules to an extracellular bath. The latter enables quantitative control over the amount of injected molecules.