Low-energy Ion Beam Bombardment Research Articles

Physiological and molecular responses of the root system of indica–japonica intersubspecific tetraploid rice seedlings to ion beam stress

Low-energy ion beam bombardment can induce various biological effects on plants, including stimulation, damage, and mutation. However, the physiological and molecular mechanisms of the stress effects of indica–japonica intersubspecific tetraploid rice seedlings roots in response to ion implantation are not fully understood. In this work, indica–japonica intersubspecific tetraploid rice seeds were implanted with different doses of ion beam to explore the responses of their seedling roots. The investigation found that that high-dose ion implantation significantly reduced the total root length, root surface area, total root volume and root tips number, significantly increased MDA content in roots, and interfered with the expression level of IAA biosynthesis and transport related genes. Under low-dose radiation, the antioxidant enzyme activity in the roots of intersubspecific tetraploid rice increased significantly compared with the control, and remained at a high level during 5–15 days of culture, without significant change. Meanwhile, the expression of IAA biosynthesis and transportation related genes were up-regulated, and the IAA content was significantly increased, which was 20.12% higher than that of the control, which finally made the root activity significantly higher than that of the parents. The aforementioned results will be useful for further research on the physiological and molecular mechanisms of indica–japonica intersubspecific tetraploid rice seedlings roots to ion beam stress.

Physiological and Molecular Responses of the Aboveground Part of Indica–Japonica Intersubspecific Tetraploid Rice Seedlings to Ion Beam Stress

Low-energy ion beam bombardment can induce various biological effects on plants, including stimulation, damage, and mutation. However, the physiological and molecular mechanisms of the biological effects of ion implantation are not fully understood. In this article, ion beam implantation was performed on Indica–Japonica intersubspecific tetraploid rice seeds to explore the responses of their seedlings. The investigation found that the aboveground part development of rice seedlings was inhibited, radiation damage was induced, and the metabolic accumulation and expression of abscisic acid (ABA) was disturbed by implantation with large doses of the low-energy $\text{N}^{+}$ beam. The activities of the antioxidant enzymes and proline (Pro) content were also increased by low-dose ion implantation induction. The malondialdehyde (MDA) content in seedlings under ion implantation was markedly higher than those of controls, and increased with the increase of ion beam irradiation doses. Transcriptional expression analysis of selected genes revealed that partly ABA anabolism genes associated with ABA production were significantly upregulated in seedlings in response to ion implantation. The aforementioned results will be useful for further research on the physiological and molecular mechanisms of Indica–Japonica intersubspecific tetraploid rice to ion beam stress.

Nonuniversality due to inhomogeneous stress in semiconductor surface nanopatterning by low-energy ion-beam irradiation

A lack of universality with respect to ion species has been recently established in nanostructuring of semiconductor surfaces by low-energy ion-beam bombardment. This variability affects basic properties of the pattern formation process, like the critical incidence angle for pattern formation, and has remained unaccounted for. Here, we show that nonuniform generation of stress across the damaged amorphous layer induced by the irradiation is a key factor behind the range of experimental observations, as the form of the stress field is controlled by the ion/target combination. This effect acts in synergy with the nontrivial evolution of the amorphous-crystalline interface. We reach these conclusions by contrasting a multiscale theoretical approach, which combines molecular dynamics and a continuum viscous flow model, with experiments using ${\text{Xe}}^{+}$ and ${\text{Ar}}^{+}$ ions on a Si(100) target. Our general approach can apply to a variety of semiconductor systems and conditions.

Large scale and orientation-controllable nanotip structures on CuInS₂, Cu(In,Ga)S₂, CuInSe₂, and Cu(In,Ga)Se₂ by low energy ion beam bombardment process: growth and characterization.

One-step facile methodology to create nanotip arrays on chalcopyrite materials (such as CuInS2, Cu(In,Ga)S2, CuInSe2, and Cu(In,Ga)Se2) via a low energy ion beam bombardment process has been demonstrated. The mechanism of formation for nanotip arrays has been proposed by sputtering yields of metals and reduction of metals induced by the ion beam bombardment process. The optical reflectance of these chalcopyrite nanotip arrays has been characterized by UV-vis spectrophotometer and the efficient light-trapping effect has been observed. Large scale (∼4'') and high density (10(10) tips/cm(2)) of chalcopyrite nanotip arrays have been obtained by using low ion energy (< 1 kV), short processing duration (< 30 min), and template-free. Besides, orientation and length of these chalcopyrite nanotip arrays are controllable. Our results can be the guide for other nanostructured materials fabrication by ion sputtering and are available for industrial production as well.

Effect of ion-beam bombardment on microstructural and magnetic properties of Ni80Fe20/α-Fe2O3 thin films

Ion-beam bombardment has been established as an effective way to tune the microstructure and thus modify the magnetic anisotropy of thin film materials, leading to certain remarkable magnetic properties. In this work, we investigated a Ni80Fe20/α-Fe2O3 bilayer deposited with a dual ion-beam deposition technique. Low-energy argon ion-beam bombardment during the α-Fe2O3 deposition led to a decline of crystallinity and interfacial roughness of the bilayer, whereas the grain size distribution remained essentially unchanged. At low temperature, the coercivity exhibited a pronounced decrease after the bombardment, indicating that the effective uniaxial anisotropy in the ferromagnetic layer was dramatically reduced. Such reduction in uniaxial anisotropy was likely attributed to the irreversible transition in the α-Fe2O3 grains caused by the ion-beam bombardment, which subsequently modified the anisotropy in the Ni80Fe20 layer. The bombarded bilayer also exhibited a larger ΔMFC–ZFC compared to the un-bombarded bilayer, which indicated a stronger exchange coupling between the ferromagnetic layer and the antiferromagnetic layer.

Induction of antioxidant enzyme activity and lipid peroxidation level in ion-beam-bombarded rice seeds

Low-energy ion beam bombardment has been used to mutate a wide variety of plant species. To explore the indirect effects of low-energy ion beam on biological damage due to the free radical production in plant cells, the increase in antioxidant enzyme activities and lipid peroxidation level was investigated in ion-bombarded rice seeds. Local rice seeds were bombarded with nitrogen or argon ion beams at energies of 29–60keV and ion fluences of 1×1016ionscm−2. The activities of the antioxidant enzymes; superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), glutathione reductase (GR), glutathione S-transferase (GST) and lipid peroxidation level were assayed in the germinated rice seeds after ion bombardment. The results showed most of the enzyme activities and lipid peroxidation levels in both the argon and nitrogen bombarded samples were higher than those in the natural control. N-ion bombardment could induce higher levels of antioxidant enzyme activities in the rice samples than the Ar-ion bombardment. Additional effects due to the vacuum condition were found to affect activities of some antioxidant enzymes and lipid peroxidation level. This study demonstrates that ion beam bombardment and vacuum condition could induce the antioxidant enzyme activity and lipid peroxidation level which might be due to free radical production in the bombarded rice seeds.

Low-energy ion beam bombardment of human cancer cells in vacuum to induce DNA transfection

A process of low-energy ion-beam-induced gene transfection in human cancer cells was developed for non-viral DNA transfection. The whole process included maintenance of the cells in vacuum, ion beam bombardment of the cells with optimized ion beam condition leading to a medium cell viability, and DNA transfer. A method of using a specially designed liquid-nitrogen cooled sample holder to house the cells and frozen medium to cover and protect the cells was adopted to maintain the cells viable in the vacuum condition during ion beam bombardment. Nitrogen ion beams with energy in the range 7–28 keV were used to bombard human cancer cells (HEp-2, the human laryngeal epitheloid cancer cell line) to fluence orders of 1015–1016 ions/cm2. After ion beam bombardment, the cell viability was studied. The ion beam condition which resulted in a relatively medium viability of the cells was chosen to operate ion bombardment to induce gene transfection. To the viable cells, DNA transfection using plasmid DNA pEGFPN2 was carried out. The experiment demonstrated that under appropriately controlled ion beam conditions and freezing environment, the human cells could survive and be transfected with exogenous DNA. This technique could be used as an alternative of non-viral gene transfections with a promising efficiency.

Tailoring interfacial exchange coupling with low-energy ion beam bombardment: Tuning the interface roughness

By ascertaining NiO surface roughness in a Ni80Fe20/NiO film system, we were able to correlate the effects of altered interface roughness from low-energy ion-beam bombardment of the NiO layer and the different thermal instabilities in the NiO nanocrystallites. From experiment and by modelling the temperature dependence of the exchange bias field and coercivity, we have found that reducing the interface roughness and changing the interface texture from an irregular to striped conformation enhanced the exchange coupling strength. Our results were in good agreement with recent simulations using the domain state model that incorporated interface mixing.

Low-energy ion beam bombardment effect on the plant-cell-envelope mimetic membrane for DNA transfer

This study is a systematic analysis of the mechanisms involved in ion-beam induced DNA transfer, an important application of ion beam biotechnology. Cellulose membranes were used to mimic the plant cell envelope. Ion beams of argon (Ar) or nitrogen (N) at an energy of 25keV bombarded the cellulose membranes at fluences ranging from 1015 to 1016ions/cm2. The damage to the ion-beam-bombarded membranes was characterized using infrared spectroscopy, a micro tensile test and scanning electron microscopy (SEM). Chain scission was the dominant radiation damage type in the membrane. DNA diffusion across the membrane was significantly increased after ion beam bombardment. The increase in DNA transfer is therefore attributed to chain scission, which increases the permeability by increasing the number of pores in the membrane.

Improved antioxidant activity of BKOS Thai jasmine rice

Thai jasmine rice (Oryza sativa L. cv. KDML105) is highly valued due to its subtle aroma, robust seed characteristics and high nutritional quality. Low-energy ion-beam bombardment was chosen to improve the quality of jasmine rice by mutation induction. One mutated variety, named BKOS, was found to exhibit a deep purple colour due to an increased accumulation of anthocyanin. The total phenolic content and antioxidant activities of cooked and uncooked rice extracts were compared with KDML105, BKOS and other rice mutants created by a low-energy ion beam. The BKOS extracts showed the highest total phenol content (0.140 and 0.096 mg of gallic acid equivalent (GAE) g−1 dry extract from uncooked and cooked rice, respectively). The BKOS extracts also had improved antioxidant activities, determined using three standard methods: 2,2′-diphenyl-1-picrylhdrazyl (DPPH) free radical scavenging, ABTS radical cation (ABTS•+) decolourisation and ferric-reducing antioxidant power assays. BKOS extracts showed 2–2.5-fold increased levels for each method. Interestingly, there was no significant difference between the antioxidant activities of the cooked and uncooked BKOS rice extracts. The increased quantity of antioxidants in this anthocyanin-based natural product could allow antioxidants to be consumed by a wider population than what is currently possible.

Ion beam modification of biological materials in nanoscale

Ion interaction with biological objects in nanoscale is a novel research area stemming from applications of low-energy ion beams in biotechnology and biomedicine. Although the ion beam applications in biotechnology and biomedicine have achieved great successes, many mechanisms remain unclear and many new applications are to be explored. We have carried out some research on exploring the mechanisms and new applications besides attaining ion beam induction of mutation breeding and gene transformation. In the studies on the mechanisms, we focused our investigations on the direct interaction in nanoscale between ions and biological living materials. Our research topics have included the low-energy ion range in DNA, low-energy ion or neutral beam bombardment effect on DNA topological form change and mutation, low-energy ion or neutral beam bombardment effect on the cell envelope and gene transformation, and molecular dynamics simulation of ultra-low-energy ion irradiation of DNA. In the exploration of new applications, we have started experiments on ion irradiation or bombardment, in the nanoscaled depth or area, of human cells for biomedical research. This paper introduces our experiments and reports interesting results.

Determination of antioxidant activity and essential element content of Thai Jasmine rice mutants induced by low energy ion-beam bombardment

Determination of antioxidant activity and essential element content of Thai Jasmine rice mutants induced by low energy ion-beam bombardment

Cloning of antifungal gene from Bacillus licheniformis by application of low energy ion beam bombardment

This work was aimed at locating the gene involved in antifungal ability of bacterium Bacillus licheniformis into yeast by application of low energy ion beam. Nitrogen ions were used to bombard the bacterial cells under vacuum condition at energy 30 keV with a fluence of 10 16 ions/cm 2. The HAT-RAPD marker revealed the modified polymorphism fragment (615 bp) presenting in the wild type but not in the bacterial mutant. This fragment was subcloned into pGEM-T easy vector and then sequenced. When the sequence of this fragment was compared with those already contained in the database, the fragment was found to be related to the lipase gene. In order to transfer the full gene, the amplified fragment of 615 bp was subcloned into a high expression vector, pYES2. Low energy ion beam was applied again but for the gene transfer into the Saccharomyces cerevisiae strain W303C. Nitrogen ions bombarded the yeast cells under vacuum condition at an energy of 50 keV with ion fluences of 5–20 × 10 15 ions/cm 2. After the treatment, the cells were screened by medium selection and restriction enzymes. The putative gene was expressed in yeast and the ability of the protein was observed by Dual culture technique with inhibition of plant disease fungal. The results provided evidence for the presence of the useful gene in the final product yeast with the assistance of low energy ion beams.

Ion-beam-induced gene transfer in Saccharomyces cerevisiae

In this paper we present a novel method to induce gene transfer in yeast ( Saccharomyces cerevisiae) using a low-energy ion beam. By accelerating nitrogen ions to the 50–60 keV energy range with ions fluences of 1–100 × 10 15 ions/cm 2, yeast cells were bombarded to characterize the decrease in survival with increasing energy level. Using bombardment conditions optimized for yeast cell survival (50 keV with ion fluences of 1 and 2 × 10 15 ions/cm 2), a compatible plasmid vector (pYES2) was successfully introduced into the yeast cell with higher concentrations of the plasmid providing improved plasmid transfer. To investigate expression of exotic genes in yeast, two marker genes – GFP and lipoic acid synthetase from Bacillus licheniformis – were chosen to subclone into pYES2 (designed pYGFP and pYlip respectively), and subsequently transformed into the cells. After 10 h of induction, the expression levels of these genes were analyzed. The pYGFP transformed yeast exhibited a high intensity of GFP protein in the yeast cells and the pYLip showed the expected additional protein-band at 34 kDa detected by SDS-polyacrylamide gel electrophoresis. As a method to transform yeast, low-energy ion beam bombardment is both highly efficient and since yeast can be transformed in less than 10 min, much more rapid than other yeast transformation methods.

Very low-energy and low-fluence ion beam bombardment of naked plasmid DNA

Ion beam bombardment of biological organisms has been recently applied to mutation breeding of both agricultural and horticultural plants. In order to explore relevant mechanisms, this study employed low-energy ion beams to bombard naked plasmid DNA. The study aimed at simulation of the final stage of the process of the ion beam bombardment of real cells to check whether and how very low-energy and low-fluence of ions can induce mutation. Argon and nitrogen ions at 5keV and 2.5keV respectively bombarded naked plasmid DNA pGFP to very low-fluences, an order of 1013ions/cm2. Subsequently, DNA states were analyzed using electrophoresis. Results provided evidences that the very low-energy and low-fluence ion bombardment indeed altered the DNA structure from supercoil to short linear fragments through multiple double strand breaks and thus induced mutation, which was confirmed by transfer of the bombarded DNA into bacteria Escherichia coli and subsequent expression of the marker gene.

Low-energy ion beam-induced mutation in Thai jasmine rice ( Oryza sativa L. cv. KDML 105)

Low-energy ion beam bombardment at energy levels in the range of 60–125 keV and ion fluences (dose) of 1 × 10 16–5 × 10 17 ions/cm 2 was chosen for mutation induction in Thai jasmine rice ( Oryza sativa L. cv. KDML 105) at Chiang Mai University. One of the rice mutants designated BKOS6 was characterized. The rice mutant was obtained from KDML 105 rice embryos bombarded with N + + N 2 + ions at an energy level of 60 keV and ion fluence of 2 × 10 16 ions/cm 2. Phenotypic variations of BKOS6 were short in stature, red/purple color in leaf sheath, collar, auricles, ligule, and dark brown stripes on leaf blade, dark brown seed coat and pericarp. The mutant's reproductive stage was found in off-season cultivation (March–July). HAT-RAPD (High Annealing Temperature-Random Amplified Polymorphic DNA) was applied for analysis of genomic variation in the mutant. Of 10 primers, two primers detected two additional DNA bands at 450 bp and 400 bp. DNA sequencing revealed that the 450 bp and the 400 bp fragments were 60% and 61% identity to amino acid sequence of flavanoid 3′hydroxylase and cytochrome P450 of O. sativa japonica, respectively.

Mutation of Bacillus licheniformis using low-energy ion beam bombardment

Anthracnose, caused by the fungus Colletotrichum sp., is an important disease affecting a wide range of flowers. To control this fungus various methods including the use of natural antagonists have been used for biological control. In this study, Bacillus licheniformis, isolated from hot springs in the Chiang Mai province, was shown to suppress conidia germination of the fungus and reduce symptoms caused by the disease in planta. To induce mutations in B. licheniformis, a low-energy ion beam was applied to the bacteria using N-ions to bombard the bacteria under vacuum conditions at an energy of 28–50 keV with a fluence range of 1–10 × 10 15 ions/cm 2. After this treatment, one mutant was found which had lost its antagonistic property. To try to characterize this mutation, the HAT–RAPD technique was used to produce band patterns for both the bombarded bacteria and the original wild type. From these polymorphic band patterns, differences were found which were induced by the ion beam. These polymorphism bands were subcloned into a pGEM-T vector and sequenced. One-band fragment conserved in the wild type and lost in the mutant bacteria was found to code for the lipase gene. Further research will focus on other genes and gene functions which may be involved in the observed antipathogenicity.

Effects of low-energy ion beam bombardment on biological cell envelopes

Low-energy ion beam biotechnology has seen rapid development worldwide in recent years. This is an important expansion of studies on ion beam modification of solid materials, vastly different from and more complex than the latter. Among other novelties, we have focused our interest on ion beam bombardment effects on plant and bacterial cell envelopes and tried to understand mechanisms involved in ion beam-induced gene transfer. Through a comprehensive investigation, we have discovered ion beam-induced formation of nanocrater-like structures in the cell envelope, a general phenomenon of ion beam bombardment of cells; these structures may act as pathways for exogenous macromolecule transfer. We have also quantitatively obtained abnormally great penetration depth and sputtering of ions in the cell envelope. All these results are significantly advantageous for ion beam processing of biological cells.

Low energy ion beam induced changes in ETFE polymer

Low energy ion beam bombardment of ethylenetetrafluoroethylene (ETFE) modifies the physical and chemical properties of the polymer surface in ways that enhance or compromise applications in the technological and medical physics fields. When a material is exposed to ionizing radiation, its changes depends on the type, energy and intensity of the applied radiation. In order to determine the nature of the induced radiation changes, ETFE films were bombarded with fluences from 1012 up to 1015ions/cm2 of keV N and protons. The emission of gaseous species during the bombardments was monitored with a residual gas analyser (RGA). The bombarded films were analysed with optical absorption photospectrometry (OAP), Fourier transform infrared (FTIR) and micro-Raman spectrometries that determine the chemical nature of the structural changes caused by ions bombardment.

Ion bombardment-induced high orientation of Al/Ti films for surface acoustic wave device applications

Al/Ti films were deposited on 128° Y-X LiNbO3 substrates by electron-beam (e-beam) deposition. Low-energy Ar ion beam bombardment was employed during the Ti underlayer deposition. Influence of low-energy beam bombardment on the texture of Al/Ti films was investigated by x-ray diffraction (XRD) analysis. It was found that Al films deposited on Ar-ion bombarded Ti underlayers possessed excellent (111) texture. With the textured Al/Ti films, a 2.3-GHz range image-impedance connection surface acoustic wave (SAW) filter was successfully fabricated.