This study explores the application of GABA-functionalized silver nanoparticles (GABAAgNPs) in nanopriming, a technique used to improve seed germination, accelerate seedling growth, and enhance plant stress tolerance. GABAAgNPs were characterized using diverse techniques, including UV-Vis, FTIR, XRD, TEM, Zeta potential, and DLS. Scanning electron microscopy (SEM) was also used to analyze the seed coat and fluorescence spectroscopy to map chlorophyll content in seedlings and nanoparticle toxicity. The results revealed the ability of GABAAgNPs to induce pore formation in the seed coat, facilitating water uptake and triggering germination processes. Furthermore, the investigation revealed that GABA undergoes metabolism within plant cells, generating glutamate. This glutamate serves as a precursor for the synthesis of aminolevulinic acid (ALA), which ultimately contributes to chlorophyll production, as evidenced by the increased vigor index and improved chlorophyll fluorescence. This work demonstrates the potential of GABAAgNPs as a novel and promising approach to promote seed germination and enhance plant resilience in sunflowers.
The relentless rise of Multidrug-Resistant (MDR) bacteria significantly challenges global health, undermining the effectiveness of traditional antibiotics and demanding prompt development of new antimicrobial strategies. This study investigates the antimicrobial properties of Gamma-Aminobutyric Acid (GABA) silver nanoparticles (GABAAgNPs). GABAAgNPs were synthesized via photoreduction and subsequently characterized using UV-Vis spectroscopy, Transmission Electron Microscopy (TEM), and Zeta potential analysis. Their antimicrobial potential was assessed through a Minimum Inhibitory Concentration (MIC) assay. The photodynamic effect was studied under irradiation at the following wavelengths: 460 +/- 10 nm (2 min), 590 nm +/- 10 nm (2 min), and 660 nm +/- 10 nm for 2, 5, and 10 minutes. Our results demonstrated that GABAAgNPs induced porphyrin formation in E. coli, leading to microbial inhibition, further enhanced through the photodynamic effect. Thus, GABAAgNPs display dual functionality: directly targeting microbes while concurrently acting as photosensitizers in antimicrobial photodynamic inactivation (aPDI).
Atherosclerosis is a narrowing of the arteries caused by an increase of atheromatous plaque: material formed by macrophage cells containing cholesterol and fatty acids, calcium and a variable amount of fibrous connective tissue. The elation between vulnerable plaques and cardiovascular events can be determined using plaque biomarkers. In this work, atherosclerotic plaques stained with different molar ratios of europium, in a potential plaque biomarker, europium tetracycline complex, were studied by fluorescence microscopy. The tetracycline antibiotic used was chlortetracycline. The growth of atherosclerotic plaque was followed during 60 days in New Zealand rabbits divided in two groups: an experimental group (EG), with nine animals and a control group (CG) with three animals. The animals in the EG received a diet with 1% of cholesterol and the animals of GC received a normal diet. The aortic arch of the animals with 60 days were cut in the vertical plane in 6 μm thick slices, which were mounted on glass slides and stained with hematoxylin an eosin and europium chlortetracycline complex (EuCTc). The fluorescence images were obtained exciting the EuCTc absorption band with a filter cube D (BP 355 – 425) and the emission was collected with a LP 470 suppression filter. Light intensity, detector gain and acquisition time were fixed for comparisons. The 20× magnified images were collected with 12 bit (or 4096 gray tones) resolution. The mean value of gray scale for each molar ratio of EuCTc was different, indicating that the complex interacts with the components of atherosclerotic plaque and the best molar ratio was 1.5 EuCTc. These results indicate the potential use of the EuCTc biomarker for atherosclerotic plaque characterization.
Metallic nanoparticles are important on several scientific, medical and industrial areas. The control of nanoparticles
characteristics has fundamental importance to increase the efficiency on the processes and applications in which they are
employed. The metallic nanoparticles present specific surface plasmon resonances (SPR). These resonances are related
with the collective oscillations of the electrons presents on the metallic nanoparticle. The SPR is determined by the
potential defined by the nanoparticle size and geometry.
There are several methods of producing gold nanoparticles, including the use of toxic chemical polymers. We already
reported the use of natural polymers, as for example, the agar-agar, to produce metallic nanoparticles under xenon lamp
irradiation. This technique is characterized as a “green” synthesis because the natural polymers are inoffensive to the
environment.
We report a technique to produce metallic nanoparticles and change its geometrical and dimensional characteristics using
a femtosecond laser. The 1 ml initial solution was irradiate using a laser beam with 380 mW, 1 kHz and 40 nm of bandwidth
centered at 800 nm.
The setup uses an Acousto-optic modulator, Dazzler, to change the pulses spectral profiles by introduction of several orders
of phase, resulting in different temporal energy distributions. The use of Dazzler has the objective of change the gold
nanoparticles average size by the changing of temporal energy distributions of the laser pulses incident in the sample. After
the laser irradiation, the gold nanoparticles average diameter were less than 15 nm.
The atheromatous plaques exhibit an accumulation of protoporphyrin IX, or PpIX, which is transferred to the feces. In this work it was associated a precursor of the PpIX, the 5-aminolevulinic acid, ALA, with gold nanoparticles (ALA:AuNps). The objective was verify the possibility to use ALA:AuNPs as a diagnosis agent for atherosclerosis. ALA:AuNps were synthesized mixing ALA with Tetrachloroauric(III) acid in miliQ water solution followed by photoreduction with light from a Xenon lamp. A total of 22 Male New Zealand rabbits were divided into 3 groups: control group (CG) where animals received normal diet, control group with ALA (CGALA ) and Experimental Group with ALA:AuNPs ( EGALAAu ) in which the animals received a diet with 1% cholesterol. Measurements of the emission intensity of extracted porphyrins from the feces in the region between 575 and 725 nm were done. An increase in the feces porphyrin emission after ALA and ALA:AuNPs administration was observed.
The use of gold nanoparticles (AuNps) as the vehicle for 5-Aminolevulinic acid (ALA) delivery for photodynamic and photothermic plasmonic therapies is a promising approach, especially with the recent demonstration that this photosensitizer immobilization on the particle surface improves reactive oxygen species (ROS) formation, increasing its cytotoxicity. Gold nanorods (AuNRs) present an absorption spectrum shifted to 700 nm, within the tissue transparency window, which allows excitation of the nanoparticles situated deeper in the tissues. Here, we describe a new synthesis method that was applied to control the shape of the gold nanoparticles during its synthesis. To obtain ALA:AuNRs, precursor ALA:AuNps were irradiated by ultrashort laser pulses. The variation of the laser parameters such as pulse energy and duration and irradiation time was assessed. The relevant mechanisms are discussed.
In this work it was used fluorescence lifetime imaging (FLIM) to analyze biochemical composition of atherosclerotic plaque. For this purpose an animal experimentation was done with New Zealand rabbits divided into two groups: a control group of 4 rabbits that received a regular diet for 0, 20, 40 and 60 days; and an experimental group of 9 rabbits, divided in 3 subgroups, that were fed with 1% cholesterol diet for 20, 40 and 60 days respectively. The aortas slices stained with europium chlortetracycline were analyzed by FLIM exciting samples at 440 nm. The results shown an increase in the lifetime imaging of rabbits fed with cholesterol. It was observed that is possible to detect the metabolic changes associated with atherosclerosis at an early stage using FLIM technique exciting the tissue around 440 nm and observing autofluorescence lifetime. Lifetimes longer than 1.75 ns suggest the presence of porphyrins in the tissue and consequently, inflammation and the presence of macrophages.
Analysis from the plasmas of rabbits subjected to high-cholesterol diets were performed by fluorescence spectroscopy using three biossensors: Europium-Chlortetracycline (EuCTc), Evans Blue (EB), and Thioflavin T (ThT). For this purpose an animal experimentation was done with New Zealand rabbits divided into two groups: control group of 6 rabbits that received a regular diet for 60 days; and experimental group of 9 rabbits, that were fed with 1% cholesterol for 60 days. The results from spectroscopic analysis have shown that the EuCTc marker emission intensity increases in the presence of plaque formation. The EB emission intensity remained constant for control and experimental groups. The ThT presented an increase in the emission intensity and a modification in the spectra shape with 60 days of diet. The studied biomarkers may not yet be specific in the
Analysis of the emissions from the corneas and aortas of rabbits subjected to high-cholesterol diets were performed by
fluorescence microscopy using the Europium Chlortetracycline (EuCTc) complex as fluorescent probe. This complex
presents absorption around 400 nm and emission around 615 nm with emission lifetime of a few microseconds, which
differs from the lifetimes of biological tissues.
The results show that EuCTc, present an intensified red fluorescence in the presence of LDL. Microscopic images
obtained using the EuCTc probe suggests that LDL is initially deposited on the luminal surface of the blood vessel,
before plaque formation. The red emission in luminal surface of the blood vessel is not observed in animals fed by 60
days with high cholesterol diet group, and the intima layer presents an increase in thickness and several red points that
indicate the presence of macrophages and foam cells. Microscopic examination of 60 days high cholesterol diet rabbits
corneas has shown that most red fluorescence occurred in the cornea epithelial cells or associated with the elongated
profiles of keratocytes. The results showed that the EuCTc probe may be useful in fluorescence angioscopy and in
clinical trials of corneal epithelial defects.
Bloodstream infections are potentially life-threatening diseases. They can cause serious secondary infections, and may
result in endocarditis, severe sepsis or toxic-shock syndrome. Pseudomonas aeruginosa is an opportunistic pathogen and
one of the most important etiological factors responsible for nosocomial infections, mainly in immuno-compromissed
hosts, characteristic of patients with severe burns. Its multiresistance to antibiotics produces many therapeutic problems,
and for this reason, the development of an alternative method to antibiotic therapy is needed. Photodynamic inactivation
(PDI) may be an effective and alternative therapeutic option to prevent bloodstream infections in patients with severe
burns. In this study we report the use of PDI to prevent bloodstream infections in mice with third-degree burns. Burns
were produced on the back of the animals and they were infected with 109 cfu/mL of multi-resistant (MR) P. aeruginosa.
Fifteen animals were divided into 3 groups: control, PDT blue and PDT red. PDT was performed thirty minutes after
bacterial inoculation using 10μM HB:La+3 and a light-emitting diode (LED) emitting at λ=460nm±20nm and a LED
emitting at λ=645 nm±10nm for 120s. Blood of mice were colected at 7h, 10h, 15h, 18h and 22h pos-infection (p.i.) for
bacterial counting. Control group presented 1×104 cfu/mL in bloodstream at 7h p.i. increasing to 1×106 at 22h, while
mice PDT-treated did not present any bacteria at 7h; only at 22h p.i. they presented 1×104cfu/mL. These results suggest
that HB:La+3 associated to blue LED or red LED is effective to delay and diminish MR P.aeruginosa bloodstream
invasion in third-degree-burned mice.
Burns are frequently contamined by pathogenic microorganisms and the widespread occurrence of antibiotic resistant
strains of Pseudomonas aeruginosa in hospitals is a matter of growing concern. Hypocrellin B (HB) is a new generation
photosensitizer extracted from the fungus Hypocrella bambusae with absorption bands at 460, 546 and 584 nm.
Lanthanide ions change the HB molecular structure and a red shift in the absorption band is observed as well as an
increase in the singlet oxygen quantum yield. In this study, we report the use of HB:La+3 to kill resistant strain of P.
aeruginosa infected burns. Burns were produced on the back of mice and wounds were infected subcutaneously with
1x109 cfu/mL of P. aeruginosa. Three-hours after inoculation, the animals were divided into 4 groups: control, HB:La+3,
blue LED and HB:La+3+blue LED. PDT was performed using 10μM HB:La+3 and 500mW light-emitting diode (LED)
emitting at λ=470nm±20nm during 120s. The animals of all groups were killed and the infected skin was removed for
bacterial counting. Mice with photosensitizer alone, light alone or untreated infected wounds presented 1x108 cfu/g while
mice PDT-treated showed a reduction of 2 logs compared to untreated control. These results suggest that HB:La+3
associated to blue LED is effective in diminishing antibiotic resistant strain P. aeruginosa in infected burns.
In this work we described the potentiality of the Hypocrellin B (HB) modified with the presence of lanthanum (La3+)
ions, in eliminate Candida albicans in suspension. The results showed that the presence of lanthanum ions promotes a
red shift of the HB absorption band and an enhancement in singlet oxygen quantum yield in 32%. Also in this work we
obtained that the best molar ration between HB and La concentrations was 1:2. No photobleaching was observed in our
experimental conditions. Antimicrobial activity was studied exciting C. albicans suspension with a 460 nm LED and a
660 nm laser both with 330 mW/cm2 irradiance. Best irradiation time, PS concentration and ROS production profile
were determined showing that using 460 nm LED with 10 μM of PS, only 30 s of irradiation time was sufficient to
reduce 100 % C. albicans colonies.
Fluorescence technique appears very important for the diagnosis of cancer. Fluorescence detection has
advantages over other light-based investigation methods: high sensitivity, high speed, and safety.
Renal cell carcinoma (RCC) accounts for approximately 3% of new cancer incidence and mortality in the United States.
Unfortunately many RCC masses remain asymptomatic and nonpalpable until they are advanced. Diagnosis and
localization of early carcinoma play an important role in the prevention and curative treatment of RCC. Certain drugs or
chemicals such as porphyrin derivatives accumulate substantially more in tumors than normal tissues.
The autofluorescence of blood porphyrin of healthy and tumor induced male SCID mice was analyzed using
fluorescence and excitation spectroscopy. A significant contrast between normal and tumor blood could be established.
Blood porphyrin fluorophore showed enhanced fluorescence band (around 630 nm) in function of the tumor growth. This
indicates that either the autofluorescence intensity of the blood fluorescence may provide a good parameter for the "first
approximation" characterization of the tumor stage.
Development of cholesterol biosensors is of great importance in clinical analysis because the concentration of
cholesterol in blood is a fundamental parameter for the prevention and diagnosis of a number of clinical disorders such
as heart disease, hypertension and arteriosclerosis. In general, determination of cholesterol is based on
spectrophotometry; but this method involves complicated procedures and the cost is high because expensive enzyme
must be used in each assay.
We report here the observation, for the first time, of the enhancement of Europium-Tetracycline complex
emission in cholesterol solutions. This enhancement was initially observed with the addition of the enzyme cholesterol
oxidase, which produces H2O2, the agent driver of the Europium tetracycline complex, to the solution. However, it was
found that the enzyme is not needed to enhance the luminescence. A calibration curve was determined, resulting in an
easy-handling immobilization method with a cheap stable material. This method shows that the complex can be used as a
sensor to determine cholesterol in biological systems with good selectivity, fast response, miniature size, and
reproducible results.
In this paper we present the spectroscopic properties of YLF:Yb:Tm:Nd system identifying the most important processes that lead to the thulium blue up conversion emission, under excitation around 792 nm. Analysis of the 475 nm emission for the samples with different concentrations of Nd3+ ions showed that energy transfer between Nd3+ and Yb3+ is the main mechanism and responsible for an enhancement in up conversion.
The tetracycline-europium (Tc-Eu) complex is known to show emission at 615 nm. On addition of hydrogen peroxide (HP), a strongly fluorescent complex is formed. In this paper it is reported that the europium fluorescence intensity is increased when urea hydrogen peroxide is added to the tetracycline-europium aqueous solution. It was conceived that this enhancement could be used to determine urea hydrogen peroxide (UHP) levels. This method is simple, practical, and relatively free of interference from coexisting substances, and it can be applied successfully to assess urea peroxide in biological samples, for example, on human whole blood. The values obtained for whole blood agree with the urea concentration variation verified in 50 patients, including 25 pre-dialysis, 15 dialysis subjects and 10 controls. This method is non invasive and can help in the identification of renal and cardiac diseases.
Compared with the traditional organic fluorescent materials, the lanthanide coordination compounds have a large variety of applications, for example glucose sensing, based on the luminescence enhancement of a lanthanide-tetracycline complex due to enzymatically generated H2O2 at physiological glucose concentrations. It is known that the fluorescence is based on the energy-transfer from the ligand to the central lanthanide ion. The aim of this work was to study the optical properties of Europium, Erbium, Ytterbium, Holmium, Terbium and Neodymium tetracycline complexes. An increase in europium emission band was observed for the first time, with addition of urea peroxide in the solution. This method works at neutral pH and the luminescence was detected at visible lanthanides luminescence after a 10 min. incubation time of the samples.
In this work we report the creation of color centers in LiF and YLF crystals by high intensity, ultrashort laser pulses. We used pure and Tm3+ and Oxygen doped samples, all irradiated with a Ti:Sapphire CPA laser system and also with electron beam, at room temperature. In both kinds of irradiations the production of photochromic damages and color centers that have absorption bands in UV and visible range was observed. A comparison between the two kinds of irradiation was done and the involved processes are described in this paper. F2+ stable centers were produced by the ultrashort laser pulses irradiation in contrast to the well-known, short lived centers produced by electron beams, and a mechanism was proposed to explain the observed stability.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.