Nanoinjection: pronuclear DNA delivery using a charged lance

Microinjection of the CRISPR/Cas9 editing system through the germ pore of a wheat microspore induces mutations in the target Ms2 gene

BACKGROUND

Microinjection is a direct procedure for delivering various compounds via micropipette into individual cells. Combined with the CRISPR/Cas9 editing technology, it has been used to produce genetically engineered animal cells. However, genetic micromanipulation of intact plant cells has been a relatively unexplored area of research, partly due to the cytological characteristics of these cells. This study aimed to gain insight into the genetic micromanipulation of wheat microspores using microinjection procedures combined with the CRISPR/Cas9 editing system targeting the Ms2 gene.

METHODS AND RESULTS

Microspores were first reprogrammed by starvation and heat shock treatment to make them structurally suitable for microinjection. The large central vacuole was fragmented and the nucleus with cytoplasm was positioned in the center of the cell. This step and an additional maltose gradient provided an adequate source of intact single cells in the three wheat genotypes. The microcapillary was inserted into the cell through the germ pore to deliver a working solution with a fluorescent marker. This procedure was much more efficient and less harmful to the microspore than inserting the microcapillary through the cell wall. The CRISPR/Cas9 binary vectors injected into reprogrammed microspores induced mutations in the target Ms2 gene with deletions ranging from 1 to 16 bp.

CONCLUSIONS

This is the first report of successful genome editing in an intact microspore/wheat cell using the microinjection technique and the CRISPR/Cas9 editing system. The study presented offers a range of molecular and cellular biology tools that can aid in genetic micromanipulation and single-cell analysis.

MoNa - A Cost-Efficient, Portable System for the Nanoinjection of Living Cells

Injection techniques to deliver macromolecules to cells such as microinjection have been around for decades with applications ranging from probing whole organisms to the injection of fluorescent molecules into single cells. A similar technique that has raised recent interest is nanoinjection. The pipettes used here are much smaller and allow for the precise deposition of molecules into single cells via electrokinetics with minimal influence on the cells’ health. Unfortunately, the equipment utilized for nanoinjection originates from scanning ion conductance microscopy (SICM) and is therefore expensive and not portable, but usually fixed to a specific microscope setup. The level of precision that these systems achieve is much higher than what is needed for the more robust nanoinjection process. We present Mobile Nanoinjection (MoNa), a portable, cost-efficient and easy to build system for the injection of single cells. Sacrificing unnecessary sub-nanometer accuracy and low ion current noise levels, we were able to inject single living cells with high accuracy. We determined the noise of the MoNa system and investigated the injection conditions for 16 prominent fluorescent labels and fluorophores. Further, we performed proof of concepts by injection of ATTO655-Phalloidin and MitoTracker Deep Red to living human osteosarcoma (U2OS) cells and of living adult human inferior turbinate stem cells (ITSC’s) following neuronal differentiation with the MoNa system. We achieved significant cost reductions of the nanoinjection technology and gained full portability and compatibility to most optical microscopes.

Intracellular Delivery by Membrane Disruption: Mechanisms, Strategies, and Concepts

Intracellular delivery is a key step in biological research and has enabled decades of biomedical discoveries. It is also becoming increasingly important in industrial and medical applications ranging from biomanufacture to cell-based therapies. Here, we review techniques for membrane disruption-based intracellular delivery from 1911 until the present. These methods achieve rapid, direct, and universal delivery of almost any cargo molecule or material that can be dispersed in solution. We start by covering the motivations for intracellular delivery and the challenges associated with the different cargo types-small molecules, proteins/peptides, nucleic acids, synthetic nanomaterials, and large cargo. The review then presents a broad comparison of delivery strategies followed by an analysis of membrane disruption mechanisms and the biology of the cell response. We cover mechanical, electrical, thermal, optical, and chemical strategies of membrane disruption with a particular emphasis on their applications and challenges to implementation. Throughout, we highlight specific mechanisms of membrane disruption and suggest areas in need of further experimentation. We hope the concepts discussed in our review inspire scientists and engineers with further ideas to improve intracellular delivery.

3D Hybrid Small Scale Devices

Interfacing nano/microscale elements with biological components in 3D contexts opens new possibilities for mimicry, bionics, and augmentation of organismically and anatomically inspired materials. Abiotic nanoscale elements such as plasmonic nanostructures, piezoelectric ribbons, and thin film semiconductor devices interact with electromagnetic fields to facilitate advanced capabilities such as communication at a distance, digital feedback loops, logic, and memory. Biological components such as proteins, polynucleotides, cells, and organs feature complex chemical synthetic networks that can regulate growth, change shape, adapt, and regenerate. Abiotic and biotic components can be integrated in all three dimensions in a well-ordered and programmed manner with high tunability, versatility, and resolution to produce radically new materials and hybrid devices such as sensor fabrics, anatomically mimetic microfluidic modules, artificial tissues, smart prostheses, and bionic devices. In this critical Review, applications of small scale devices in 3D hybrid integration, biomicrofluidics, advanced prostheses, and bionic organs are discussed.

A review of genetic engineering biotechnologies for enhanced chronic wound healing

Traditional methods for addressing chronic wounds focus on correcting dysfunction by controlling extracellular elements. This review highlights technologies that take a different approach - enhancing chronic wound healing by genetic modification to wound beds. Featured cutaneous transduction/transfection methods include viral modalities (ie adenoviruses, adeno-associated viruses, retroviruses and lentiviruses) and conventional non-viral modalities (ie naked DNA injections, microseeding, liposomal reagents, particle bombardment and electroporation). Also explored are emerging technologies, focusing on the exciting capabilities of wound diagnostics such as pyrosequencing as well as site-specific nuclease editing tools such as CRISPR-Cas9 used to both transiently and permanently genetically modify resident wound bed cells. Additionally, new non-viral transfection methods (ie conjugated nanoparticles, multi-electrode arrays, and microfabricated needles and nanowires) are discussed that can potentially facilitate more efficient and safe transgene delivery to skin but also represent significant advances broadly to tissue regeneration research.

CRISPR-Cas9 directed knock-out of a constitutively expressed gene using lance array nanoinjection

Background

CRISPR-Cas9 genome editing and labeling has emerged as an important tool in biologic research, particularly in regards to potential transgenic and gene therapy applications. Delivery of CRISPR-Cas9 plasmids to target cells is typically done by non-viral methods (chemical, physical, and/or electrical), which are limited by low transfection efficiencies or with viral vectors, which are limited by safety and restricted volume size. In this work, a non-viral transfection technology, named lance array nanoinjection (LAN), utilizes a microfabricated silicon chip to physically and electrically deliver genetic material to large numbers of target cells. To demonstrate its utility, we used the CRISPR-Cas9 system to edit the genome of isogenic cells. Two variables related to the LAN process were tested which include the magnitude of current used during plasmid attraction to the silicon lance array (1.5, 4.5, or 6.0 mA) and the number of times cells were injected (one or three times).

Results

Results indicate that most successful genome editing occurred after injecting three times at a current control setting of 4.5 mA, reaching a median level of 93.77 % modification. Furthermore, we found that genome editing using LAN follows a non-linear injection-dose response, meaning samples injected three times had modification rates as high as nearly 12 times analogously treated single injected samples.

Conclusions

These findings demonstrate the LAN’s ability to deliver genetic material to cells and indicate that successful alteration of the genome is influenced by a serial injection method as well as the electrical current settings.

The effect of injection speed and serial injection on propidium iodide entry into cultured HeLa and primary neonatal fibroblast cells using lance array nanoinjection

Background

Although site-directed genetic engineering has greatly improved in recent years, particularly with the implementation of CRISPR-Cas9, the ability to deliver these molecular constructs to a wide variety of cell types without adverse reaction is still a challenge. One non-viral transfection method designed to address this challenge is a MEMS based biotechnology described previously as lance array nanoinjection (LAN). LAN delivery of molecular loads is based upon the combinational use of electrical manipulation of loads of interest and physical penetration of target cell membranes. This work explores an original procedural element to nanoinjection by investigating the effects of the speed of injection and also the ability to serially inject the same sample.

Results

Initial LAN experimentation demonstrated that injecting at speeds of 0.08 mm/s resulted in 99.3 % of cultured HeLa 229 cells remaining adherent to the glass slide substrate used to stage the injection process. These results were then utilized to examine whether or not target cells could be injected multiple times (1, 2, and 3 times) since the injection process was not pulling the cells off of the glass slide. Using two different current control settings (1.5 and 3.0 mA) and two different cell types (HeLa 229 cells and primary neonatal fibroblasts [BJ(ATCC^® CRL-2522™)], treatment samples were injected with propidium iodide (PI), a cell membrane impermeable nucleic acid dye, to assess the degree of molecular load delivery. Results from the serial injection work indicate that HeLa cells treated with 3.0 mA and injected twice (×2) had the greatest mean PI uptake of 60.47 % and that neonatal fibroblasts treated with the same protocol reached mean PI uptake rates of 20.97 %.

Conclusions

Both experimental findings are particularly useful because it shows that greater molecular modification rates can be achieved by multiple, serial injections via a slower injection process.

Transient Low-Temperature Effects on Propidium Iodide Uptake in Lance Array Nanoinjected HeLa Cells

Understanding environmental factors relative to transfection protocols is key for improving genetic engineering outcomes. In the following work, the effects of temperature on a nonviral transfection procedure previously described as lance array nanoinjection are examined in context of molecular delivery of propidium iodide (PI), a cell membrane impermeable nucleic acid dye, to HeLa 229 cells. For treatment samples, variables include varying the temperature of the injection solution (3C and 23C) and the magnitude of the pulsed voltage used during lance insertion into the cells (+5 V and +7 V). Results indicate that PI is delivered at levels significantly higher for samples injected at 3C as opposed to 23C at four different postinjection intervals (t = 0, 3, 6, 9 mins; p-value ≤ 0.005), reaching a maximum value of 8.3 times the positive control for 3 C/7 V pulsed samples. Suggested in this work is that between 3 and 6 mins postinjection, a large number of induced pores from the injection event close. While residual levels of PI still continue to enter the treatment samples after 6 mins, it occurs at decreased levels, suggesting from a physiological perspective that many lance array nanoinjection (LAN) induced pores have closed, some are still present.

Injection of Propidium Iodide into HeLa Cells Using a Silicon Nanoinjection Lance Array

Delivering foreign molecules into human cells is a wide and ongoing area of research. Gene therapy, or delivering nucleic acids into cells via nonviral or viral pathways, is an especially promising area for pharmaceutics. All gene therapy methods have their respective advantages and disadvantages, including limited delivery efficiency and low viability. We present an electromechanical method for delivering foreign molecules into human cells. Nanoinjection, or delivering molecules into cells using a solid lance, has proven to be highly efficient while maintaining high viability levels. This paper describes an array of solid silicon microlances that was tested to determine efficiency and viability when nanoinjecting tens of thousands of HeLa cells simultaneously. Propidium iodide (PI), a dye that fluoresces when bound to nucleic acids and does not fluoresce when unbound, was delivered into cells using the lance array. Results show that the lance array delivers PI into up to 78% of a nanoinjected HeLa cell culture, while maintaining 78–91% viability. With these results, we submit the nanoinjection method using a silicon lance array as another promising particle delivery method for mammalian culture cells.

A self-reconfiguring metamorphic nanoinjector for injection into mouse zygotes

This paper presents a surface-micromachined microelectromechanical system nanoinjector designed to inject DNA into mouse zygotes which are ≈90 μm in diameter. The proposed injection method requires that an electrically charged, DNA coated lance be inserted into the mouse zygote. The nanoinjector's principal design requirements are (1) it must penetrate the lance into the mouse zygote without tearing the cell membranes and (2) maintain electrical connectivity between the lance and a stationary bond pad. These requirements are satisfied through a two-phase, self-reconfiguring metamorphic mechanism. In the first motion subphase a change-point six-bar mechanism elevates the lance to ≈45 μm above the substrate. In the second motion subphase, a compliant folded-beam suspension allows the lance to translate in-plane at a constant height as it penetrates the cell membranes. The viability of embryos following nanoinjection is presented as a metric for quantifying how well the nanoinjector mechanism fulfills its design requirements of penetrating the zygote without causing membrane damage. Viability studies of nearly 3000 nanoinjections resulted in 71.9% of nanoinjected zygotes progressing to the two-cell stage compared to 79.6% of untreated embryos.

Electrotriggered, spatioselective, quantitative gene delivery into a single cell nucleus by Au nanowire nanoinjector

Delivery of bioactive materials into a cell is highly important in the study of cell biology and medical treatments. Ideal nanoinjectors should be able to deliver biomaterials with high spatial resolution while causing minimum cell damage. We developed a Au nanowire (NW) nanoinjector that has the thinnest diameter (100–150 nm) among the DNA delivering devices as well as optimum mechanical properties, minimizing cell damage. Well-defined (111) single-crystalline Au surface and high electric conductivity of a Au NW nanoinjector allow precisely timed and efficient electrochemical release of DNA molecules attached on a Au NW surface. Both linear DNA and plasmid DNA were delivered separately and showed successful expression. The Au NW nanoinjector would find important biomedical applications in the fields such as gene therapy, DNA vaccination, targeted drug delivery, and probe/control of cell signaling events.

Transgene delivery via intracellular electroporetic nanoinjection

Development of an effective cytoplasmic delivery technique has remained an elusive goal for decades despite the success of pronuclear microinjection. Cytoplasmic injections are faster and easier than pronuclear injection and do not require the pronuclei to be visible; yet previous attempts to develop cytoplasmic injection have met with limited success. In this work we report a cytoplasmic delivery method termed intracellular electroporetic nanoinjection (IEN). IEN is unique in that it manipulates transgenes using electrical forces. The microelectromechanical system (MEMS) uses electrostatic charge to physically pick up transgenes and place them in the cytoplasm. The transgenes are then propelled through the cytoplasm and electroporated into the pronuclei using electrical pulses. Standard electroporation of whole embryos has not resulted in transgenic animals, but the MEMS device allows localized electroporation to occur within the cytoplasm for transgene delivery from the cytoplasm to the pronucleus. In this report we describe the principles which allow localized electroporation of the pronuclei including: the location of mouse pronuclei between 21 and 28 h post-hCG treatment, modeling data predicting the voltages needed for localized electroporation of pronuclei, and data on electric-field-driven movement of transgenes. We further report results of an IEN versus microinjection comparative study in which IEN produced transgenic pups with viability, transgene integration, and expression rates statistically comparable to microinjection. The ability to perform injections without visualizing or puncturing the pronuclei will widely benefit transgenic research, and will be particularly advantageous for the production of transgenic animals with embryos exhibiting reduced pronuclear visibility.