Injection Apparatus Research Articles

Evaluation of Ecological Parameters of a Compression Ignition Engine Fueled by Diesel Oil with an Eco Fuel Shot Liquid Catalyst

This article discusses the potential applications of the Fuel Shot liquid catalyst in compression ignition (CI) engines for reducing toxic substances in exhaust gases. Incorporating catalysts into fuel can optimize the combustion process, consequently reducing the emission of toxic substances into the atmosphere. Toxic compounds, such as nitrogen oxides, particulate matter, and hydrocarbons, adversely affect flora and fauna. Various methods are known for reducing their concentration in engine exhaust gases, one of which is the Fuel Shot liquid catalyst. The authors conducted experiments on a Fiat 1.3 JTD engine with a Common Rail system. The results indicate that the application of the liquid catalyst reduces the content of nitrogen oxides and hydrocarbons in the exhaust gases and slightly decreases fuel consumption. Additionally, investigations were carried out on the engine’s injection apparatus, which was fueled with modified fuel. The findings demonstrate that the fuel additive does not affect the wear of precision parts of fuel injectors and high-pressure pumps.

Application of Machine Learning to Classify the Technical Condition of Marine Engine Injectors Based on Experimental Vibration Displacement Parameters

The article presents the possibility of using machine learning (ML) in artificial intelligence to classify the technical state of marine engine injectors. The technical condition of the internal combustion engine and injection apparatus significantly determines the composition of the outlet gases. For this purpose, an analytical package using modern technology assigns experimental test scores to appropriate classes. The graded changes in the value of diagnostic parameters were measured on the injection subsystem bench outside the engine. The influence of the operating conditions of the fuel injection subsystem and injector condition features on the injector needle vibration displacement waveforms was subjected to a neural network (NN) ML process and then tested. Diagnostic parameters analyzed in the amplitude, frequency, and time–frequency domains were subjected after a learning process to recognize simulated various regulatory and technical states of suitability and unfitness with single and complex damage of new and worn injector nozzles. Classification results were satisfactory in testing single damage and multiple changes in technical state characteristics for unfitness states with random wear injectors. Testing quality reached above 90% using selected NNs of Statistica 13.3 and MATLAB R2022a environments.

Performance Comparison of Trunk Injection Mechanisms for Ganoderma Control

A severe disease known as Ganoderma Boninense, which attacks a group of wood-decaying fungi, causes Basal Stem Rot (BSR) in oil palm trees. One of the treatments introduced to control the spread is injecting a chemical into the palm's trunk. After receiving a hexaconazole treatment for a year, a study on 2008 Ganoderma-infected palm trees in an estate revealed that 95.6% of the infected palms were still standing. The injection process facilitates several devices that were used and invented. These machines utilise a pressure-injection technique that injects a chemical through a flexible hose into a healthy palm's tissue to prevent the disease from spreading. Hence, the development of effective trunk injector mechanisms for Ganoderma treatment is discussed in this article. The first injection method utilised the Pressure Injection Apparatus (PIA), which can deliver a chemical to the target sites to control BSR. Second, a Mechanical Trunk Injector mainly facilitated chemical injection into the palm trunk using a prime mover. Next, the Tractor Mounted Trunk Injector, comprised of an injection apparatus system, was found to perform effectively and efficiently. The distribution profile of the dye eosin in the stem revealed that it covered more than 80% of the cross-sectional and longitudinal axes of the palm tree's trunk. Instead of the previous injection apparatus control method, this machine could speed up the injection time. Compared to the 20-minute-per-hole completion time of the PIA, the machine only took 3 to 5 minutes to complete an injection, which was 65% faster, and about 100 to 120 palms could be covered in a day. Labour requirements were very minimal as it is a single-operated machine. Utilising the machine would also result in a reduction in the number of workers needed.

A novel equation to calculate primary drainage capillary pressure based on a porous plate model: Theory and application

This study aims to develop an equation for primary drainage capillary pressure as a function of water saturation based on the porous plate model. Several empirical and semiempirical equations are available to calculate Pc-Sw. The results of the previous equations are not ideal, so this is an attempt to present an accurate equation to calculate Pc-Sw based on governing theoretical physical analysis to describe two-phase immiscible displacement flow in porous media. Volumetric flow rates through the core plug and porous plate are applied to calculate the transport phenomena in porous media. The equation is derived from mass and momentum transfer through a core plug, and Darcy’s law is applied to water flow through a porous plate. Finally, the modified Bessel function is obtained to calculate Pc as a function of Sw. The findings of this study help provide a better understanding of two-phase immiscible displacement flow in porous media. The novelty of this work lies in the ability of the new Pc-Sw equation to accurately fit the primary drainage capillary pressure experimental data obtained from a porous plate, centrifugal, and mercury injection apparatus without restriction. The new equation can be used to calculate the relative permeability and initial fluid distribution in the reservoir. The accuracy of the new equation is a significant advantage compared to Brooks-Corey's Pc-Sw equation; therefore, the research results lead to an incremental advance in the field. This study fills the gap between analytical and empirical models to find the Pc-Sw equation.

Analysing the bone cement flow in the injection apparatus during vertebroplasty

AbstractVertebroplasty, a medical procedure for treating vertebral fractures, requires medical practitioners to inject bone cement inside the vertebra using a cannula attached to a syringe. The required injection force must be small enough for the practitioner to apply it by hand while remaining stable for a controlled injection. Several factors could make the injection force unintuitive for the practitioners, one of them being the non‐Newtonian nature of the bone cement. The viscosity of the bone cement varies as it flows through the different parts of the injection apparatus and the porous cancellous interior of the vertebra. Therefore, it is important to study the flow of bone cement through these parts. This work is a preliminary study on the flow of bone cement through the injection apparatus. Firstly, we obtained the rheological parameters for the power law model of bone cement using experiments using standard clinical equipment. These parameters were then used to obtain the shear rate, viscosity, and velocity profiles of the bone cement flow through the cannula. Lastly, an analysis was carried out to understand the influence of various geometrical parameters of the injection apparatus, in which the radius of the cannula was found to be the most influential parameter.

Pharmacokinetics of Monoclonal Antibody and Antibody Fragments in The Mouse Eye Following Intravitreal Administration

Mice are rarely used in pharmacokinetic (PK) studies of ocular therapeutics due to the small size of their eyes and challenges in drug administration, tissue collection, and analysis of drug concentrations. Therefore, ocular PK of protein therapeutics in mouse eye following intravitreal (IVT) administration is not known. Here, we have presented the first of its kind investigation, to study the PK of 4 different size non-binding protein therapeutics in mouse plasma, cornea/ICB, vitreous humor, retina, and posterior cup (including choroid) following IVT administration. Administered proteins include trastuzumab (150 kDa) and F(ab)2 (100 kDa), Fab, and scFv (27 kDa) fragments of trastuzumab. An imaging and injection apparatus suitable for performing small (50 nL) IVT injections in mice was developed, and techniques for enucleation of the eye and dissection of ocular tissues were developed. Furthermore, a sensitive enzyme-linked immunosorbent assay (ELISA) for detection of proteins in very small amounts of ocular tissues were developed. It was observed that elimination from the vitreous chamber was the primary driver of PK in the cornea/ICB, retina, posterior cup, and plasma. Trastuzumab displays first-order kinetics in the vitreous humor with a half-life of 18.8 h. F(ab)2, Fab, and ScFv show biphasic PK profiles with distribution phases becoming more rapid as molecular weight decreases, and terminal elimination becoming longer as molecular weight decreases, with terminal half-lives of 16.3, 20.6, and 48.9 h, respectively. The mean residence times of trastuzumab, F(ab)2, Fab, and scFv in the vitreous humor were 26.0, 12.2, 10.7, and 8.16 h, respectively. It was found that the mean residence time in vitreous humor doubles with an increase in molecular weight of ∼69 kDa. Interestingly, the PK of proteins measured in the un-injected eye suggest the presence of a pathway for drug transfer between the eyes, which needs to be further validated. Overall, the findings presented here pave the way for drug discovery and development studies of protein therapeutics for ophthalmic indications in mice.

Hydrogen-Containing “Green” Fuels Influence on the Thermal Protection and Formation of Wear Processes Components in Compression-Ignition Engines Modern Injection System

The article describes the impact of hydrogen-containing vegetable fuels consumption with modern injection apparatus. The fuel in question is B100 rapeseed oil ethyl ester. The process of atomizing fuel in the engine at high temperature and in a high pressure chamber plays an important role in the combustion processes in the CI engine. The elements responsible for supplying fuel to the engine’s combustion chamber are the injectors and the injection pump. The paper presents the construction and operation of modern injection pumps and fuel injectors, the methods of their diagnosis are discussed, the important role of precision, and the course of their wear phenomenon are indicated. The paper discusses the impact of hydrogen-containing “green” vegetable fuels on the durability and reliability of injection pumps and fuel injectors used in Common Rail systems. In addition, the tests on the operating parameters of the fuel injector and pump operating on conventional fuel and hydrogen-containing “green” biofuel were carried out.

Rate-Controlled Mercury Injection Experiments to Characterize Pore Space Geometry of Berea Sandstone

Interpretation of the relationship between heterogeneity and the flow in porous media is very important in increasing the recovery factor for an oil or gas reservoir. Capillarity for instance, controls fluids static distribution in a reservoir prior to production and remaining hydrocarbons after production commences. Therefore, capillary pressure data are used by petroleum engineers, geologists, and petrophysicists to evaluate production characteristics of petroleum accumulations. Conventional pressure-controlled mercury porosimetry produces an overall capillary pressure curve and pore throat size distribution data that provide little information about the porous medium structure and pore geometry. The present study provides information on three capillary pressure curves obtained from rate-controlled mercury injection porosimetry; one describes the larger pore spaces or pore bodies of a rock, another describes the smaller pores or pore throats that connect the larger pores, and a final curve which corresponds to the overall capillary pressure curve obtained from the conventional pressure-controlled mercury injection. An experimental constant-rate mercury injection apparatus was constructed that consists of a piston displacement pump, a computer controlled stepper motor drive and a core sample cell designed to minimize dead volume. The apparatus was placed in a glass chamber and subjected to an air bath to maintain a constant temperature of 27o C throughout the experiments. Then constant rate mercury injection experiments were performed on three Berea Sandstone core plugs. Results show that volume-controlled or rate-controlled porosimetry provides considerably more detailed data and information on heterogeneity and the statistical nature of pore space structure than the conventional pressure-controlled porosimetry as pressure fluctuations with time reveal menisci locations in pore bodies and pore throats. Moreover, pore size distributions based on volume-accessed pores and pore radii were obtained from the pressure versus saturation relationship.

Method and a Device for Testing the Friction Force in Precision Pairs of Injection Apparatus of the Self-Ignition Engines

This article reviews the state of the knowledge and technology in the field of friction-loss measurements in internal combustion piston engines. The dependencies that describe the loss of energy in combustion engines and injection apparatus are presented. Currently, very little can be found in the literature on the study of frictional forces in injection apparatus, but mainly in the piston–cylinder group, so this work significantly fills that gap. The aim of this article is to construct a device and to develop a method for assessing the technical state of injector nozzles to minimize friction losses in internal combustion engines at the stages of evaluation, design, production and operation. This article presents a stand for determining the maximum friction forces due to gravity loading by water-jet control. This article also presents test results on the maximum friction force between a needle and a body of injector nozzles in piston combustion engines on a designed and purpose-built stand outside of the combustion engine. Various designs and injector nozzles are made from various types of alloy steel for marine and automotive piston internal combustion engines fueled with distillation or residual fuels, and are tested. The research concerned conventional elements for the injection apparatus as well as electronically controlled subsystems. Precision pairs of injection equipment are selected for the tests: new ones are employed after the storage period and operated in natural conditions. The elements dismantled from the internal combustion engines are tested in the presence of fuel or calibration oil of similar properties. The maximum static frictional forces under the hydrostatic loading are measured, alongside the parameters for the dynamic movement of the nozzle needles from bodies of the injector nozzle as time, speed, acceleration and dynamic force. The influence of the angular position of the needle in relation to the bodies of the precision pairs conventional internal combustion engines, the diametral clearance between the nozzle body and needle, and the surface conditions on the values of the maximum friction force are also presented. Errors in shape and position result in the uniqueness of the friction force at the mutual angular position of the needle in relation to the nozzle body, and the decrease in diametral clearance and deterioration of the surface state increase the friction losses. A model was elaborated of the influence of various factors on the value of the maximum friction force.

How Much Does Filler Apparatus Influence Ease of Injection (and Hence, Potential Safety)?

To document the relative contributions of intrinsic filler fluid dynamics versus delivery systems for ease of injection-specifically, to measure extrusion force variability across different syringes and needles (with the characterization of intrinsic rheological fluid properties vs. delivery apparatus contributions to ease of injection). Six different fillers were tested: Belotero balance (Bel), Juvederm Voluma XC (Vol), Revanesse Versa (Rev), Restylane Lyft (Res), Radiesse (Rad), and Teosyal RHA3 (RHA). Extrusion force was measured in Newtons (N) for each by testing using the provided injection apparatus (needle + syringe), and also by standardizing all fillers to the same syringe and then varying needle sizes (30-ga, 27-ga, 25-ga/1.5-inch, 25-ga/2-inch, and 22-ga). Five trials were conducted for each scenario, with comparison via t -test (2-tailed, unpaired, assuming unequal variance). The following results were noted: (1) in order of least to highest extrusion force in box-provided syringe + needle at 0.2 ml volume, the following were noted: Vol < RHA = Bel (27-ga) < Bel (30-ga) < Rev < Res = Rad; (2) for each filler (except for Vol which was similar), the box-provided syringe involved greater extrusion force than the standardized syringe used in this study (each 1-cc, p < 0.05); (3) for 27-ga and 30-ga needles, after standardization of delivery syringe at 0.2 ml volume, a significant difference was noted (proportional to increasing resistance): Bel = Vol = RHA3 < Res < Rev < Rad (for needles of 30-ga [ p < 0.05] and 27-ga [ p < 0.01]); (4) for testing cannulas after standardization of syringes no reproducible order was noted with increasing resistance when using 25-ga/1.5-inch long, 25-ga/2-inch, and 22g/2-inch cannulae; and (5) confirming expectation (validating study technique), the extrusion force was significantly higher for smaller needles and longer needles. The delivery apparatus appeared to be the most influential contributor to filler injection extrusion force, with significant changes in ease of injection correlated to the filler's intrinsic rheological properties, such as viscosity (when standardized to the same syringe for needles tested). Knowledge of such data could influence the injector's ability to maximize patients' safety and clinical results.

Study on the effect of coal microscopic pore structure to its spontaneous combustion tendency

Coal is a porous medium. Due to the large number of pores in coal and the pore size on its surface, usually ranging from millimeter to nanometer, it is difficult to measure and analyze the microscopic pore structure of coal. In order to investigate the effect of the microscopic pore structure of coal on its spontaneous combustion tendency, coal samples from different coal mines of the Kailuan Group were selected as the research objects, and the data of the microscopic pore distribution of three different coal samples were measured by using mercury injection apparatus. The regression analysis of microscopic pore data of coal samples obtained in the mercury injection experiment shows that the correlation coefficients of the regression curves are all greater than 0.94 and the fitting degree is good, indicating that there is a good correlation between the pressure, mercury intake and pore size of the coal samples, indicating that the fractal dimension of pore distribution is very effective. The fractal dimension is generally between 2 and 3, indicating that the microscopic pores of coal samples have good fractal characteristics and meet the fractal theory to describe the distribution characteristics of microscopic pores in porous media. Through the simulation system of natural combustion of coal, the simulation experiment of temperature rise oxidation of different coal samples (gas coal, fat coal, and coke coal) was carried out, and the curve of the concentration of gas products CO and CO2 in the process of temperature rise and oxidation of coal samples was drawn in the experiment. The experimental results show the relationship between the distribution structure of coal pores and its spontaneous combustion tendency, and the coal with a good distribution dimension has a stronger combustion tendency

Improving the mechanical property and water resistance of β-hemihydrate phosphogypsum by incorporating ground blast-furnace slag and steel slag

This research work mainly explored the solid waste cementitious material by incorporating ground blast-furnace slag (GBFS) and steel slag (SS) into the β-hemihydrate phosphogypsum (β-HPG) system. The optimum ratio of GBFS/SS was attempted to be found by referring to the ternary contour design method, and the hydration and hardening mechanism of binary systems of β-HPG -GBFS and β-HPG -SS and ternary system of β-HPG -GBFS-SS was investigated. Contour distributions of the compressive strength of pastes with 60–100% β-HPG, and 0–40% GBFS and SS content at the age of 2 h, 1 d, 7 d, and 28 d were analyzed. The further study focused on the performance change rule of the experimental groups with 60% content of β-HPG under different GBFS/SS ratio. Hydration products of these hardened paste samples were characterized by X-ray diffraction (XRD), thermo-gravimetric analysis (TG), 27Al solid-state nuclear magnetic resonance (27Al-NMR). Hydration heat was used to evaluate the hydration process. Pore structure was verified by mercury injection apparatus (MIP) and scanning electron microscope (SEM). The results showed that in comparison with the pure β-HPG system, the compressive strength was improved greatly, the softening coefficient was increased largely, and the water absorption rate was reduced in the β-HPG-GBFS-SS ternary system. Comprehensive consideration of mechanical property and water resistance, results showed that the test group composed of 60% β-HPG, 30% GBFS and 10% SS was the best experimental scheme, and the reasons behind were discussed in detail. These conclusions were hoped to provide significative guidance for the comprehensive utilization of β-HPG, GBFS and SS.

Mechanical performance, hydration characteristics and microstructures of high volume blast furnace ferronickel slag cement mortar by wet grinding activation

Replacement of cement clinker by industrial wastes has been verified as an effective way to reduce carbon emissions. To realize the application of blast furnace ferronickel slag (BFFS) in high volume in cement mortar, wet grinding was used to improve the activity of BFFS. Three fineness (D50 = 13 μm, 5 μm and 2.5 μm) and three contents (30%, 50% and 70%) of BFFS were investigated comparatively. Isothermal calorimetry, X-ray diffractometer(XRD), Thermal analyzer (TG), Fourier Transform Infrared (FTIR), Mercury injection apparatus (MIP) and Scanning Electron Microscope (SEM) were employed to examine the hydration process and microstructures. The results showed that the pozzolanic behavior and filling effect of BFFS could be improved remarkably by wet-grinding method. The compressive strength of specimens with 50mirc% and 70% BFFS (D50 = 2.5 μm) after curing 28 days could reach 109% and 97% of that of control cement specimens respectively. The results of XRD, TG and FTIR revealed that refined BFFS was involved in pozzolanic reaction at age of 3 days, the effect was more significant with the grinding duration extending. Furthermore, the pore size distribution and the porosity were optimized obviously. Results highlight that wet-grinding treatment of BFFS provided an effective way to improve the early and late age strength of high-volume BFFS cement mortar.

Study on the Effects of Powder-Liquid Ratio and Cement Ratio on Mechanical Properties and Microscopic Characteristics of Polymer-Cement Composite

This paper is about a study on the mechanical properties of a new polymer-cement composite (PCC) in constant elongation, tension, and shear. The study explored the effects of powder-liquid ratio and cement ratio on the mechanical properties of PCC through detecting the strength, deformation, and energy consumption of specimens under different powder-liquid ratios and cement ratios. In addition, scanning electron microscope and mercury injection apparatus were used for an in-depth analysis on the micromorphology and pore structure features of PCC under different powder-liquid ratios and cement ratios to explore the influence of powder-liquid ratio and cement ratio of the micromechanical properties of PCC. The results showed that, with the increase of powder-liquid ratio and cement ratio, the constant elongation adhesion strength of PCC decreased, and, at a high powder-liquid ratio (0.55) or a high cement ratio (0.5), the constant elongation adhesion strength of PCC completely disappeared. Meanwhile, with the increase of powder-liquid ratio and cement ratio, the tensile shear strength of PCC increased, while the deformation capacity of PCC decreased. The optimal ranges of powder-liquid ratio and cement ratio for PCC were 0.35–0.4 and 0.3-0.4, respectively. Furthermore, the increased powder-liquid ratio and cement ratio made the total pore volume decreased and pore structure refined, which improved the compactness of PCC, thus influencing the performance of PCC macroscopically. An achievement for the study is a flexible composite material, which was formulated with the polymer film as continuous base phase, as well as the inorganic composition and cement hydrates as dispersion phase. The material can effectively improve the economy and practicability of cementation of fissures for airfield pavement.

Optimization of Design and Technology of Injector Nozzles in Terms of Minimizing Energy Losses on Friction in Compression Ignition Engines

The operation of injection apparatus in self-ignition engines results from the design, manufacturing technology and wear and tear during operation. The technical state of the injector apparatus significantly affects the engine performance, fuel consumption, toxicity and smoke opacity of outlet gases. The most unreliable element of the injection apparatus is the injector nozzle, the quality of which depends on the quality of construction and production, operating conditions and the of the fuels used, etc. One of the design parameters of the injector nozzles, determining the technical state is the geometry of the nozzle holes. An attempt was made to optimize the selection of the dimensions and surface condition of the spray holes to significantly affect the flow properties of the injector nozzles and, consequently, to decide on the size and form of fuel dosed streams to individual cylinders of a self-ignition engine and the quality of fuel atomization. In work, a simulation model was developed, and the pressure losses and the mass fluid of the injected fuel were minimized for selected significant geometric features, taking into account the influence of operating conditions. With the use of Mathematica software, simulation optimization methods and methods based on evolutionary algorithms were elaborated.

Tumor Allotransplantation in Drosophila melanogaster with a Programmable Auto-Nanoliter Injector.

This protocol describes the allotransplantation of tumors in Drosophila melanogaster using an auto-nanoliter injection apparatus. With the use of an autoinjector apparatus, trained operators can achieve more efficient and consistent transplantation results compared to those obtained using a manual injector. Here, we cover topics in a chronological fashion: from the crossing of Drosophila lines, to the induction and dissection of the primary tumor, transplantation of the primary tumor into a new adult host and continued generational transplantation of the tumor for extended studies. As a demonstration, here we use Notch intracellular domain (NICD) overexpression induced salivary gland imaginal ring tumors for generational transplantation. These tumors can first be reliably induced in a transition-zone microenvironment within larval salivary gland imaginal rings, then allografted and cultured in vivo to study continued tumor growth, evolution, and metastasis. This allotransplantation method can be useful in potential drug screening programs, as well as for studying tumor-host interactions.

Experimental studies on elastic properties of high density polyethylene-multi walled carbon nanotube nanocomposites

The effect of nanoparticle volume fraction on the elastic properties of a polymer-based nanocomposite was experimentally investigated and the obtained results were compared with various existing theoretical models. The nanocomposite was consisted of high density polyethylene (HDPE) as polymeric matrix and 0, 0.5, 1 and 1.5 wt.% multi walled carbon nanotubes (MWCNTs) prepared using twin screw extruder and injection molding technique. Nanocomposite samples were molded in injection apparatus according to ASTM-D638 standard. Therefore, in addition to morphological investigations of the samples, tensile tests at ambient temperature were performed on each sample and stress-strain plots, elastic moduli, Poisson's ratios, and strain energies of volume units were extracted from primary strain test results. Tensile test results demonstrated that 1 wt.% nanoparticles presented the best reinforcement behavior in HDPE-MWCNT nanocomposites. Due to the agglomeration of nanoparticles at above 1 wt.%, Young' s modulus, yielding stress, fracture stress, and fracture energy were decreased and Poisson's ratio and failure strain were increased.

Study on antifreeze Properties and pore structure of Basalt Fiber Reinforced Concrete

We designed basalt fiber concrete with a volume content of 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%. Through the mass loss rate and dynamic modulus loss rate after different freezing-thawing cycles, the antifreeze performance of concrete was tested. As the internal capillary pores of concrete are the main channel for corrosive medium and other harmful substances to invade the internal concrete, the durability of concrete is closely related to the internal pore structure. The microstructure and pore structure of basalt fiber concrete were tested by sem and Mercury Injection Apparatus, so as to analyze the microstructure of the interface between fiber and cement and discuss the strengthening mechanism of basalt fiber concrete. The results indicate that the basalt fiber can improve the freeze-thaw cycle of concrete With the increase of the content of basalt fiber, the gel has greater adhesion and binding force to basalt fiber, and the hydration products attached to the surface of basalt fiber gradually decrease When the content of basalt fiber is 0.3%, the frost resistance of concrete is the best. The addition of basalt fiber optimizes the hole structure and reduces the internal defects of concrete, thus improving the durability.

Solving the Puzzle: Connecting a Heterologous Agrobacterium tumefaciens T6SS Effector to a Pseudomonas aeruginosa Spike Complex.

The type VI secretion system (T6SS) is a contractile injection apparatus that translocates a spike loaded with various effectors directly into eukaryotic and prokaryotic target cells. Such T6SS spike consists of a needle-shaped trimer of VgrG proteins topped by a conical and sharp PAAR protein that facilitates puncturing of the target membrane. T6SS-delivered effector proteins can be either fused to one of the two spike proteins or interact with either in a highly specific manner. In Agrobacterium tumefaciens the T6SS effector Tde1 is targeted to its cognate VgrG1 protein. Here, we attempted to use a VgrG shuttle to deliver a heterologous T6SS effector by directing Tde1 onto a T6SS spike in Pseudomonas aeruginosa. For this, we designed chimeras between VgrG1 from A. tumefaciens and VgrG1a from P. aeruginosa and showed that modification of the spike protein hampered T6SS functionality in the presence of the Tde1 effector complex. We provide evidence suggesting that Tde1 specifically binds to the VgrG spike in the heterologous environment and propose that there are additional requirements to allow proper effector delivery and translocation. Our work sheds light on complex aspects of the molecular mechanisms of T6SS delivery and highlights some limitations on how effectors can be translocated using this nanomachine.

Manipulating the type VI secretion system spike to shuttle passenger proteins.

The type VI secretion system (T6SS) is a contractile injection apparatus that translocates a spike loaded with various effectors directly into eukaryotic or prokaryotic target cells. Pseudomonas aeruginosa can load either one of its three T6SSs with a variety of toxic bullets using different but specific modes. The T6SS spike, which punctures the bacterial cell envelope allowing effector transport, consists of a torch-like VgrG trimer on which sits a PAAR protein sharpening the VgrG tip. VgrG itself sits on the Hcp tube and all elements, packed into a T6SS sheath, are propelled out of the cell and into target cells. On occasion, effectors are covalent extensions of VgrG, PAAR or Hcp proteins, which are then coined “evolved” components as opposed to canonical. Here, we show how various passenger domains could be fused to the C terminus of a canonical VgrG, VgrG1a from P. aeruginosa, and be sent into the bacterial culture supernatant. There is no restriction on the passenger type, although the efficacy may vary greatly, since we used either an unrelated T6SS protein, β-lactamase, a covalent extension of an “evolved” VgrG, VgrG2b, or a Hcp-dependent T6SS toxin, Tse2. Our data further highlights an exceptional modularity/flexibility for loading the T6SS nano-weapon. Refining the parameters to optimize delivery of passenger proteins of interest would have attractive medical and industrial applications. This may for example involve engineering the T6SS as a delivery system to shuttle toxins into either bacterial pathogens or tumour cells which would be an original approach in the fight against antimicrobial resistant bacteria or cancer.