Development of the particle inflow gun for DNA delivery to plant cells

Summary A simple and inexpensive particle bombardment device was constructed for delivery of DNA to plant cells. The Particle Inflow Gun (PIG) is based on acceleration of DNA-coated tungsten particles using pressurized helium in combination with a partial vacuum. The particles are accelerated directly in a helium stream rather than being supported by a macrocarrier. Bombardment parameters were partially optimized using transient expression assays of a ß-glucuronidase gene in maize embryogenic suspension culture and cowpea leaf tissues. High levels of transient expression of the ß-glucuronidase gene were obtained following bombardment of embryogenic suspension cultures of corn and soybean, and leaf tissue of cowpea. Stable transformation of embryogenic tissue of soybean has also been obtained using this bombardment apparatus.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - PCV packed cell volume - GUS ß-glucuronidase - NOS nopaline synthase Salaries and research support were provided by State and Federal funds appropriated to OSU/OARDC and USDA-ARS. Mention of trademark of proprietary products does not constitute a guarantee or warranty of the product by OSU/OARDC or USDA, and also does not imply approval to the exclusion of other products that may also be suitable. Journal Article No. 34-92     

The role of particle size distribution on bioavailability of cyclosporine: novel drug delivery system

During the long period of cyclosporine-containing dosage forms development a lot of significant findings have been done especially in the field of drug delivery systems. Currently available drugs are based, from technological point of view, on self-dispersible drug delivery systems, which contain cyclosporine solved in pharmaceutically acceptable vehicle. One can find difference among particular systems a) at particle size distribution after dispergation, b) at composition and c) at bioavailability of cyclosporine. As far as improvement of bioavailability between original brand leader formulation Sandimmune and recent brand leader formulation Neoral was followed by significant improvement in particle size distribution it was generally assumed that the reason for this improvement have been found. Several other formulations e.g. Consupren or SangCyA--self-dispersible systems, more or less correspond with above mentioned theory that smaller is better and by this principle bridged liquid based dosage forms with solid dosage forms. Bioavailability of novel drug delivery system which gives coarse dispersion with average particle size between 1-150 microns when dispersed have been tested on healthy volunteers. No difference among pharmacokinetic parameters of novel drug delivery system and microemulsion system have been observed in spite of fact that average particle size of novel system is almost 1000x bigger.     

Mesoscopic dynamics of colloids simulated with dissipative particle dynamics and fluid particle model

We report results of numerical simulations of complex fluids, using a combination of discrete-particle methods. Our molecular modeling repertoire comprises three simulation techniques: molecular dynamics (MD), dissipative particle dynamics (DPD), and the fluid particle model (FPM). This type of model can depict multi-resolution molecular structures (see the Figure) found in complex fluids ranging from single micelle, colloidal crystals, large-scale colloidal aggregates up to the mesoscale processes of hydrodynamical instabilities in the bulk of colloidal suspensions. We can simulate different colloidal structures in which the colloidal beds are of comparable size to the solvent particles. This undertaking is accomplished with a two-level discrete particle model consisting of the MD paradigm with a Lennard-Jones (L-J) type potential for defining the colloidal particle system and DPD or FPM for modeling the solvent. We observe the spontaneous emergence of spherical or rod-like micelles and their crystallization in stable hexagonal or worm-like structures, respectively. The ordered arrays obtained by using the particle model are similar to the 2D colloidal crystals observed in laboratory experiments. The micelle shape and its hydrophobic or hydrophilic character depend on the ratio between the scaling factors of the interactions between colloid–colloid to colloid–solvent. Unlike the miscellar arrays, the colloidal aggregates involve the colloid–solvent interactions prescribed by the DPD forces. Different from the assumption of equilibrium growth, the two-level particle model can display much more realistic molecular physics, which allows for the simulation of aggregation for various types of colloids and solvent liquids over a very broad range of conditions. We discuss the potential prospects of combining MD, DPD, and FPM techniques in a single three-level model. Finally, we present results from large-scale simulation of the Rayleigh–Taylor instability and dispersion of colloidal slab in 2D and 3D. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00894-001-0068-3.Electronic Supplementary Material available.     

Regeneration and transformation of Egyptian maize inbred lines via immature embryo culture and a biolistic particle delivery system

Summary A regeneration system was developed for elite Egyptain maize inbred lines using immature embryos as explants. This system proved to be highly genotype-dependent. Line Gz 643 was identified as the best line, revealing the highest regeneration frequency (42.2%). Addition of l-proline and silver nitrate to culture media greatly enhanced the formation of embryogenic type II callus and the regenerability of some of the tested lines. Transformation of the scutellar tissue of immature embryos from inbred line Gz643 was performed with the particle delivery system using a single plasmid carrying both the GUS and Bar genes (pAB-6) or by co-transformation with two plasmids, pAct1-F (GUS) and pTW-a(Bar). Different transformation parameters were evaluated, i.e. ostomic treatment, acceleration pressure, and number of shots. Osmotic treatment (0.25 M sorbitol + 0.25 M mannitol) along with the use of either acceleration pressure 1300 psi and one shot per plate (for co-transformation with pAB-6) or 1100 psi and two shots per plate (for transformation with pAct1-F and pTW-a) gave the best results, as expressed by the number of blue spots in the β-glucuronidase (GUS) assay. Stable transformation was confirmed in Ro transformed plants by means of histochemical GUS assay and herbicide application. PCR and Southern blot analysis proved the integration of the full-length genes in some of the transgenics.     

Optimization of a jet-propelled particle injection system for the uniform transdermal delivery of drug/vaccine

A jet-propelled particle injection system, the biolistics, has been developed and employed to accelerate micro-particles for transdermal drug delivery. We have examined a prototype biolistic device employing a converging-diverging supersonic nozzle (CDSN), and found that the micro-particles were delivered with a wide velocity range (200-800 m/s) and spatial distribution. To provide a controllable system for transdermal drug delivery, we present a contoured shock-tube (CST) concept and its embodiment device. The CST configuration utilizes a quasi-steady, quasi-one dimensional and shock-free supersonic flow to deliver the micro-particles with an almost uniform velocity (the mean velocity and the standard deviation, 699 +/- 4.7 m/s) and spatial distribution. The transient gas and particle dynamics in both prototype devices are interrogated with the validated computational fluid dynamics (CFD) approach. The predicted results for static pressure and Mach number histories, gas flow structures, particle velocity distributions and gas-particle interactions are presented and interpreted. The implications for clinical uses are discussed.     

尼莫地平自微乳化释药系统处方优化

目的:制备尼莫地平的自微乳化释药系统.方法:通过溶解度实验筛选各种辅料,按照处方设计制得系列自微乳化液,并通过体外评价以确定最优处方.结果:最优处方为尼莫地平、聚氧乙烯氢化蓖麻油-35、油酸乙酯和单辛酸甘油酯的质量百分数分别为3.5%、40%、40%和16.5%.在0.1 mo1 oL-1稀盐酸中轻微搅拌,该优化处方能够在1 min内迅速乳化,得到粒径均值58.6 nm的乳滴,1 min时的溶出率为84.3%.结论:按优化处方制得的尼莫地平自微乳化释药系统显著提高了尼莫地平的溶出.     

Development of a new aerosol delivery system for systemic pulmonary delivery in anaesthetized and orotracheal intubated rats.

Over the last decade, the systemic absorption of a broad range of therapeutics after pulmonary application has been demonstrated in animals as well as in humans. The most common method used in the laboratory is the intratracheal instillation of drugs in solution. This method is, however, unsatisfactory, because of discrepancies in particle distribution, clearance, kind of injury and bioavailability between instillation and inhalative application. On the other hand, a precise determination of the amount of drug applied by aerosol, and of the aerosol volume retained within the lungs is rather difficult, and is not possible for use with small animals such as mice or rats. We describe a system which allows the delivery of aerosols directly into the animal's lungs, and calculation of the amount of drug retained in the lungs. Our system was tested in vitro and in vivo and was shown to allow precise and efficient pharmacokinetic and toxicological studies to be carried out.     

Development of polymeric drug delivery system for recognizing vascular endothelial dysfunction

The vascular endothelium plays an important role in regulating vascular homeostasis. Damage to the endothelium can lead to cardiovascular diseases such as arteriosclerosis. Therefore, early-stage detection and evaluation of vascular endothelium dysfunction would be very important for effective diagnosis and therapy. We synthesized a polymeric drug carrier bearing an Evans blue analogue as a probing unit for endothelium injury. The polymeric carrier spontaneously formed stable nanoparticles with micelle-like structure in aqueous media and could encapsulate hydrophobic doxorubicin (DOX). The encapsulated DOX showed a sustainable release profile over a period of 10-60 h depending on the loaded DOX concentration. The polymeric carrier specifically adsorbed against the endothelium-injured site in extracted porcine aorta. These properties of the polymeric drug carrier will be suitable for specific drug delivery to endothelium dysfunctional region.     

Development of target delivery system based on actinomycin class drugs and recombinant alpha-fetoprotein

A recombinant alpha-fetoprotein (rAFP) was obtained in the yeast P. pastoris system, and its functional activity was confirmed. A method for producing polymer particles loaded with dactinomycin was developed, and a conjugate of these nanoparticles with rAFP was synthesized. The efficiency of the obtained conjugate on the HeLa, SKOV3, and MG-63 tumor cells and the absence of toxicity on the normal cells was shown. Experiments in vivo demonstrated a significant increase in the antitumor efficacy of the conjugate at a lower general toxicity as compared to the commercially available dactinomycin.     

Formulation of a dry powder influenza vaccine for nasal delivery

The purpose of this research was to prepare a dry powder vaccine formulation containing whole inactivated influenza virus (VIIV) and a mucoadhesive compound suitable for nasal delivery. Powders containing WIIV and either lactose or trehalose were produced by lyophilization. A micro-ball mill was used to reduce the lyophilized cake to sizes suitable for nasal delivery. Chitosan flakes were reduced in size using a cryo-milling technique. Milled powders were sieved between 45 and 125 μm aggregate sizes and characterized for particle size and distribution, morphology, and flow properties. Powders were blended in the micro-ball mill without the ball. Lyophilization followed by milling produced irregularly shaped, polydisperse particles with a median primary particle diameter of ≈21 μm and a yield of ≈37% of particles in the 45 to 125 μm particle size range. Flow properties of lactose and trehalose powders after lyophilization followed by milling and sieving were similar. Cryo-milling produced a small yield of particles in the desired size range (<10%). Lyophilization followed by milling and sieving produced particles suitable for nasal delivery with different physicochemical properties as a function of processing conditions and components of the formulation. Further optimization of particle size and morphology is required for these powders to be suitable for clinical evaluation. Published: March 10, 2006     

Liposomal dry powders as aerosols for pulmonary delivery of proteins

The purpose of this research was to develop liposomal dry powder aerosols for protein delivery. The delivery of stable protein formulations is essential for protein subunit vaccine delivery, which requires local delivery to macrophages in the lungs. β-Glucuronidase (GUS) was used as a model protein to evaluate dry powder liposomes as inhaled delivery vehicles. Dimyristoyl phosphatylcholine:cholesterol (7∶3) was selected as the liposome composition. The lyophilization of liposomes, micronization of the powders, aerosolization using a dry powder inhaler (DPI), and in vitro aerodynamic fine particle fraction upon collection in a twinstage liquid impinger were evaluated. After lyophilization and jet-milling, the total amount of GUS and its activity, representing encapsulation efficiency and stability, were evaluated. The GUS amount and activity were measured and compared with freshly-prepared liposomes in the presence of mannitol, 43% of initial GUS amount, 29% of GUS activity after lyophilization and 36% of GUS amount, 22% of activity after micronization were obtained. Emitted doses from dry powder inhaler were 53%, 58%, 66%, and 73% for liposome powder:mannitol carrier ratios of 1∶0, 1∶4, 1∶9, and 1∶19. Fifteen percent of the liposome particles were less than 6.4 μm in aerodynamic diameter. The results demonstrate that milled liposome powders containing protein molecules can be aerosolized effectively at a fixed flow rate. Influences of different cryoprotectants on lyophilization of protein liposome formulations are reported. The feasibility of using liposomal dry powder aerosols for protein delivery has been demonstrated but further optimization is required in the context of specific therapeutic proteins. Published: December 21, 2005     

Transfection of liver in vivo by biolistic particle delivery

We describe the delivery of reporter gene constructs to rat liver through the use of the Helios Gene Gun system. The effectiveness of this transfection method is illustrated by describing its use for determining in vivo the role of a DNA element that regulates cytochrome P450 2B1 (CYP2B1) gene expression in response to xenobiotics. DNA was delivered to the liver of an anesthetized animal via DNA-coated gold microcarriers. The highest level of reporter gene expression was obtained about six hours posttransfection; however, at this time endogenous CYP2B1 mRNA is transiently induced by the anesthetic treatment. The optimal time for investigating expression of a reporter gene under the control of CYP2B1 regulatory elements was 24 h after transfection, by which time the inductive effect of the anesthetic had ceased. Reporter gene expression subsequently declined rapidly to a low level by 48 h. In the transfected liver the heterologous SV40 promoter was about eight-fold stronger than the minimal CYP2B1 promoter. However, when attached to the phenobarbital response element both promoters give the same fold-induction of reporter activity in response to phenobarbital.     

Development of a novel probiotic delivery system based on microencapsulation with protectants

The establishment of the health-promoting benefits of probiotics is challenged by the antimicrobial bio-barriers throughout the host’s gastrointestinal (GI) tract after oral administration. Although microencapsulation has been frequently utilised to enhance the delivery of probiotics, microcapsules of sub-100 μm were found to be ineffective and therefore questioned as an effective delivery vehicle for viable probiotics despite the sensory advantage. In this study, four probiotics strains were encapsulated in chitosan-coated alginate microcapsules of sub-100 μm. Only a minor protective effect was observed from this original type of microcapsule. In order to enhance the survival of these probiotics, sucrose, a metabolisable sugar, and lecithin vesicles were added to the wall material. Both of the ingredients could be readily encapsulated with the probiotics, and protected them from stresses in the simulated GI fluids. The metabolisable sugar effectively increased the survival of the probiotics in gastric acid, mainly through energizing the membrane-bound F₁F₀-ATPases. The lecithin vesicles proved to alleviate the bile salt stress, and hence notably reduced the viability loss at the elevated bile salt concentrations. Overall, three out of the total four probiotics in the reinforced sub-100 μm microencapsules could significantly survive through an 8-h sequential treatment of the simulated GI fluids, giving less than 1-log drop in viable count. The most vulnerable strain of bifidobacteria also yielded a viability increase of 3-logs from this protection. In conclusion, the sub-100 μm microcapsules can be a useful vehicle for the delivery of probiotics, as long as suitable protectants are incorporated in the wall matrix.     

Development and application of an insertional system for gene delivery and expression in Campylobacter jejuni

The genetic investigation of Campylobacter jejuni, an important gastrointestinal pathogen, has been hampered by the lack of an efficient system for introduction of exogenous genetic information, as commonly used vectors designed for Escherichia coli and other bacteria cannot be maintained in Campylobacter cells. Additionally, gene expression in Campylobacter requires the presence of species-specific promoters. In this study we exploited the availability of several conserved copies of rRNA gene clusters for insertion of various genes into the chromosome by homologous recombination. The high conservation of the rRNA sequences means that the procedure can be applied to other Campylobacter strains. The presence of a Campylobacter-derived promoter in this vector ensures expression of exogenous genes in target cells. The efficiency of the procedure was demonstrated by complementation of mutations in two strains of Campylobacter. In addition, we applied the system for introduction and expression of a green fluorescent protein (GFP). GFP-expressing Campylobacter allowed visualization of sessile bacteria attached to a glass surface in stationary liquid culture. The study demonstrated that the attached bacteria contained an assemblage of coccoid and spiral forms with liquid channels preserving viable highly motile cells. We demonstrate a novel universal procedure for gene delivery and expression that can be used as an efficient tool to study this poorly understood pathogen. The principles developed in this study could be more widely applied for the manipulation of other bacteria that are refractory to genetic analysis.     

Improved intracellular delivery of oligonucleotides by square wave electroporation

Prior studies have shown that electroporation is a simple and effective method for the introduction of oligonucleotides (ODN) into cells. In ex vivo bone marrow purging models, electroporation of ODN into cells has been associated with selective killing of human neoplastic cells while sparing hematopoietic stem cells. Prior studies used conventional electroporation methods (i.e., exponential decay) to introduce ODN into cells. Square wave electroporation allows the delivery of a more defined and regulated electrical pulse and is associated with high transfection efficiencies in a variety of systems. The current study was undertaken to determine whether square wave electroporation was more effective than exponential decay electroporation for the delivery of ODN into hematopoietic cells. Using fluorescein-tagged ODN and K562, chronic myelogenous leukemia (CML) cells, higher transfection rates were observed after square wave electroporation. In addition, c-myc antisense ODN were more effective in reducing c-myc protein when introduced by square wave electroporation, as compared with introduction by exponential decay electroporation. Square wave electroporation is thus identified as the optimal method for delivering ODN into hematopoietic cells.     

Preparation of dry powder dispersions for non-viral gene delivery by freeze-drying and spray-drying

Background

Dry powder dispersion devices offer potential for delivering therapeutic macromolecules to the pulmonary epithelia. Previously, freeze‐drying (lyophilisation) has been the accepted method for preparing dried formulations of proteins and non‐viral gene vectors despite the respirability of such powders being inadequate without further processing. In this study we compare the utility of freeze‐drying and spray‐drying, a one‐step process for producing dry and respirable powders, as methods for preparing non‐viral respiratory gene delivery systems.

Methods

Lipid:polycation:pDNA (LPD) vectors comprising 1,2‐dioleoyl‐3‐trimethylammoniumpropane (DOTAP), protamine sulphate and pEGFP‐N1 in 3% lactose solution were either snap‐frozen and lyophilised or spray‐dried. Lyophilised powder was used as recovered or following coarse grinding. Structural integrity of dehydrated pDNA was assessed by agarose gel electrophoresis and powder particle size determined by laser diffraction. The apparent structure of the systems was visualised by scanning and transmission electron microscopy with the biological functionality quantified in vitro (A549 human lung epithelial cell line) by Green Fluorescent Protein (GFP) associated fluorescence.

Results

Lyophilisation produced large, irregularly shaped particles prior to (mean diameter ～21 µm) and following (mean diameter ～18 µm) coarse grinding. Spray‐drying produced uniformly shaped spherical particles (mean diameter ～4 µm). All dehydrated formulations mediated reporter gene expression in A549 cells with the spray‐dried formulation generally proving superior even when compared with freshly prepared LPD complexes. Biological functionality of the LPD dry powders was not adversely affected following 3 months storage.

Conclusions

Spray‐drying has utility for producing stable, efficient and potentially respirable non‐viral dry powder systems for respiratory gene delivery. Copyright © 2002 John Wiley & Sons, Ltd.