Biomedical subjects

Joseph Irudayaraj

Publications and source records attributed to Joseph Irudayaraj.

17 recordsLinked to original sources

PubMed2025

Retinal hypoxia reversal with PLGA-oxygen nanobubbles.

Pathologies associated with retinal hypoxia, including diabetic retinopathy, central/branch retinal artery occlusion (CRAO/BRAO), central/branch retinal vein occlusion (CRVO/BRVO), retinopathy of prematurity, sickle cell retinopathy, etc., have limited effective therapeutic intervention strategies. To address this shortcoming, herein we propose a biocompatible and biodegradable poly (lactic-co-glycolic acid) shell-based oxygen nanobubbles (PLGA-ONBs) platform, formulated with PLGA, polyvinyl alcohol (PVA), and NaHCO3. The formulation of a novel PLGA-ONBs was proposed, and the synthesis process was optimized with respect to dependent (sonication power, PVA, and NaHCO3 concentrations) and response (hydrodynamic diameter and oxygen capacity) variables. The optimized formulation has a concentration of (13.8 ± 0.01) × 1010 particles per ml with a hydrodynamic diameter of 142.83 ± 11.46 nm, and oxygen loading capacity of 47.2 ± 2.4 mg L-1. After 4 weeks of storage, the ONBs were found to have an oxygen concentration of 38.9 ± 2.9 mg L-1, indicating excellent oxygen retention capability. The PLGA-ONBs tested in vitro in Muller and R28 retinal cell lines demonstrated excellent biocompatibility and potential to mitigate hypoxia. In addition, the PLGA-ONBs treatment on hypoxic cells demonstrated restoration of mRNA expression of three key hypoxic genes (HIF-1α, PAI-1, and VEGF-A) to normoxic states, indicating hypoxia reversal potential. Biosafety of the PLGA-ONBs was demonstrated in a rabbit model, demonstrating promise in clinical translation. The PLGA-ONBs developed exhibited excellent oxygen loading and retention, potential in hypoxia mitigation, and a safety profile that could be a promising route to treating ischemic diseases of the eye.

Polylactic Acid-Polyglycolic Acid Copolymer↗

PubMed2007

Multiplex biosensor using gold nanorods.

Gold nanorods (GNRs) with different aspect ratios were fabricated through seed-mediated growth and surface activation by alkanethiols for the attachment of antibodies to yield gold nanorod molecular probes (GNrMPs). Multiplex sensing was demonstrated by the distinct response of the plasmon spectra of the GNrMPs to binding events of three targets (goat anti-human IgG1 Fab, rabbit anti-mouse IgG1 Fab, rabbit anti-sheep IgG (H+L)). Plasmonic sensors are highly specific and sensitive and can be used to monitor refractive index changes caused by molecular interactions in their immediate vicinity with potential to achieve single-particle biosensing. This technique can play a key role in developing novel optical biosensors for both in vivo and in vitro detection and single-receptor kinetics.

Animals↗

PubMed2006

Characterization of human breast epithelial cells by confocal Raman microspectroscopy.

BACKGROUND: The past decade has seen an explosion of interest in utilizing Raman spectroscopy in cancer diagnosis, due to its capability to probe changes in the biochemical composition of tissue that accompany disease progression. However, most of the existing methods used multivariate statistical analysis/chemometrics to differentiate normal and diseased tissues, which did not identify the compositional and chemical changes associated with the tumorigenic transition explicitly; also the sub-cellular level spatial resolution achievable through Confocal Raman microscopy was not fully utilized. METHODS: Confocal Raman microspectroscopy was used to characterize normal and transformed human breast epithelial cell lines. Key molecular components (DNA, RNA, and proteins) were extracted from cell nuclei and their Raman spectra were measured and used as a basis set to fit the spectra of cell nuclei. Contributions of each component and their relative contents were evaluated based on the fitting coefficients. RESULTS: Spectrum-fitting revealed that DNA duplication activities in tumorigenic cell nuclei are significantly higher than in normal cells. The fitting coefficients could serve as good spectral markers for disease state identification. CONCLUSIONS: A spectroscopic approach that yields compositional information of cell nuclei could be a powerful tool for rapid cell characterization and assessment of cellular activities at the sub-cellular level.

Breast↗

PubMed2006

A nanoparticle-based immobilization assay for prion-kinetics study.

Magnetic and gold coated magnetic nanoparticles were synthesized by co-precipitation of ferrous and ferric chlorides, and by the micromicelles method, respectively. Synthesized nanoparticles were functionalized to bear carboxyl and amino acid moieties and used as prion protein carriers after carbodiimide activation in the presence of N-hydroxysuccinimide. The binding of human recombinant prion protein (huPrPrec) to the surface of these nanoparticles was confirmed by FTIR and the size and structures of the particles were characterized by transmission electron microscopy. Findings indicate that the rate of prion binding increased only slightly when the concentration of prion in the reaction medium was increased. Rate constants of binding were very similar on Fe3O4@Au and Fe3O4-LAA when the concentrations of protein were 1, 2, 1.5, 2.25 and 3.57 microg/ml. For a 5 microg/ml concentration of huPrPrec the binding rate constant was higher for the Fe3O4-LAA particles. This study paves the way towards the formation of prion protein complexes onto a 3-dimensional structure that could reveal obscure physiological and pathological structure and prion protein kinetics.

Journal Article↗

PubMed2006

Magnetic and gold-coated magnetic nanoparticles as a DNA sensor.

In this study, we report the chemical synthesis and functionalization of magnetic and gold-coated magnetic nanoparticles and the immobilization of single-stranded biotinylated oligonucleotides onto these particles. Selected sequences specific to the BRCA1 gene were used as a test platform. The binding of oligonucleotides to these particles was achieved through a streptavidin-biotin bridge via a carbodiimide activation protocol. Particle size and oligonucleotide attachment were confirmed by transmission electron microscopy; oligonucleotide binding was characterized by Fourier transform infrared spectroscopy and hybridization confirmed by fluorescence emission from the fluorophore attached to the target oligonucleotide strand. The rate of hybridization was measured using a spectrofluorometer and a microarray scanner. The rate of hybridization of oligonucleotides bound to the synthesized particles depends on the inorganic support material and its surface chemistry. The rate of hybridization increased concomitantly with the concentration of the probe and the target in the reaction medium. Furthermore, exposure of probe and target oligonucleotide to a combination of target and noncomplementary DNA strand reduced the rate of hybridization, possibly because of steric crowding in the reaction medium and cross-linking between reacting oligonucleotides and the noncomplementary strands. The study undertaken opens several possibilities in bioconjugate attachment to functionalized iron and iron nanocomposite structures for controlled manipulation and handling using magnetic fields.

DNA↗

PubMed2006

Mid-IR biosensor: detection and fingerprinting of pathogens on gold island functionalized chalcogenide films.

Antibody (human IgG, anti-E. coli O157:H7, and anti-Salmonella) complexes on the surface of IR-transparent Ge-containing chalcogenide glass films were formed via thiol chemistry on 20-nm-thick gold islands. As a first step, the protocol was validated by monitoring fluorescently tagged targets to validate binding. FT-IR spectroscopy confirmed that the coating of the films with 20-nm gold did not have a significant effect on the propagation and penetration of IR evanescent waves through the film. The films functionalized with anti-E. coli O157:H7 and anti-Salmonella antibodies were used to detect E. coli O157:H7 and S. enteriditis through label-free IR fingerprinting. Highly selective detection of bacterial targets was achieved at both the species (E. coli vs. S. enteriditis) and strain level (E. coli O157:H7 vs E. coli K12). A mid-infrared approach could thus be used as a biosensor as well as a molecular fingerprinting tool.

Antibodies, Bacterial↗

PubMed2006

A mixed self-assembled monolayer-based surface plasmon immunosensor for detection of E. coli O157:H7.

The sensitivity and specificity of a polyethylene glycol terminated alkanethiol mixed self-assembled monolayers (SAM) on surface plasmon resonance (SPR) immunosensor to detect Escherichia coli O157:H7 is demonstrated. Purified monoclonal (Mabs) or polyclonal antibodies (PAbs) against E. coli O157:H7 were immobilized on an activated sensor chip and direct and sandwich assays were carried to detect E. coli O157:H7. Effect of Protein G based detection and effect of concentrations of primary and secondary antibodies in sandwich assay were investigated. The sensor surface was observed under an optical microscope at various stages of the detection process. The sensor could detect as low as 10(3)CFU/ml of E. coli O157:H7 in a sandwich assay, with high specificity against Salmonella Enteritidis. The detection limit using direct assay and Protein G were 10(6)CFU/ml and 10(4)CFU/ml, respectively. Results indicate that an alkanethiol SAM based SPR biosensor has the potential for rapid and specific detection of E. coli O157:H7, using a sandwich assay.

Antigen-Antibody Complex↗

PubMed2006

Discrimination of irradiated starch gels using FT-Raman spectroscopy and chemometrics.

The effects of gamma-irradiation on starch gels were characterized at the molecular level by Fourier transform (FT) Raman spectroscopy. Starches from five different sources were gelatinized and irradiated at 3, 5, and 10 kGy using a Co60 gamma-irradiator. Gamma-irradiation effects on starch gels were noted by the C-H stretch (2800-3000 cm(-1)) and O-H stretch (3000-3600 cm(-1)) and bend (1600-1800 cm(-1)) regions of the FT-Raman spectra. FT-Raman molecular fingerprints obtained through spectral analyses were used for discrimination of the gels based on the extent of irradiation by means of two different pattern-recognition techniques: canonical variate analysis (CVA) and soft modeling of class analogy (SIMCA). A complete discrimination of irradiated starches was attained using a hybrid partial least-squares (PLS) and CVA model, using the spectral variations in the C-H stretch and O-H stretch and bend regions of FT-Raman spectra. Using the same spectral regions, SIMCA predicted 84% of samples correctly.

Chemical Phenomena↗

PubMed2005

Spectroscopic characterization of microorganisms by Fourier transform infrared microspectroscopy.

Spectroscopic fingerprints of bacteria were investigated by Fourier transform infrared (FTIR) microspectroscopy for the elucidation of chemical composition and structural information during growth. Good differentiation of six microorganisms was achieved down to the strain level. The inherent compositional and structural differences of cell envelopes and cytoplasm were investigated and utilized to obtain more detailed analysis of the spectroscopic features. Bands or regions of key functional groups were also identified in the original spectra. Microspectroscopic monitoring of bacterial growth demonstrated that FTIR spectroscopy cannot only provide molecular fingerprints of the cell envelope, but also compositional and metabolic information of the cytoplasm under different physiological conditions. This approach could be an effective alternative to traditional nutritional and biochemical methods to monitor and assess the effects of inhibitors and other environmental factors on microbial cell growth.

Escherichia coli↗

PubMed2005

Activity of glucose oxidase functionalized onto magnetic nanoparticles.

BACKGROUND: Magnetic nanoparticles have been significantly used for coupling with biomolecules, due to their unique properties. METHODS: Magnetic nanoparticles were synthesized by thermal co-precipitation of ferric and ferrous chloride using two different base solutions. Glucose oxidase was bound to the particles by direct attachment via carbodiimide activation or by thiophene acetylation of magnetic nanoparticles. Transmission electron microscopy was used to characterize the size and structure of the particles while the binding of glucose oxidase to the particles was confirmed using Fourier transform infrared spectroscopy. RESULTS: The direct binding of glucose oxidase via carbodiimide activity was found to be more effective, resulting in bound enzyme efficiencies between 94-100% while thiophene acetylation was 66-72% efficient. Kinetic and stability studies showed that the enzyme activity was more preserved upon binding onto the nanoparticles when subjected to thermal and various pH conditions. The overall activity of glucose oxidase was improved when bound to magnetic nanoparticles CONCLUSION: Binding of enzyme onto magnetic nanoparticles via carbodiimide activation is a very efficient method for developing bioconjugates for biological applications.

Journal Article↗

PubMed2005

Examination of Cholesterol oxidase attachment to magnetic nanoparticles.

Magnetic nanoparticles (Fe3O4) were synthesized by thermal co-precipitation of ferric and ferrous chlorides. The sizes and structure of the particles were characterized using transmission electron microscopy (TEM). The size of the particles was in the range between 9.7 and 56.4 nm. Cholesterol oxidase (CHO) was successfully bound to the particles via carbodiimide activation. FTIR spectroscopy was used to confirm the binding of CHO to the particles. The binding efficiency was between 98 and 100% irrespective of the amount of particles used. Kinetic studies of the free and bound CHO revealed that the stability and activity of the enzyme were significantly improved upon binding to the nanoparticles. Furthermore, the bound enzyme exhibited a better tolerance to pH, temperature and substrate concentration. The activation energy for free and bound CHO was 13.6 and 9.3 kJ/mol, respectively. This indicated that the energy barrier of CHO activity was reduced upon binding onto Fe3O4 nanoparticles. The improvements observed in activity, stability, and functionality of CHO resulted from structural and conformational changes of the bound enzyme. The study indicates that the stability and activity of CHO could be enhanced via attachment to magnetic nanoparticles and subsequently will contribute to better uses of this enzyme in various biological and clinical applications.

Journal Article↗

PubMed2004

Quantification of saccharides in multiple floral honeys using fourier transform infrared microattenuated total reflectance spectroscopy.

Fourier transform infrared (FTIR) spectroscopy with microattenuated total reflectance (mATR) sampling accessory and chemometrics (partial least squares and principal component regression) was used for the simultaneous determination of saccharides such as fructose, glucose, sucrose, and maltose in honey. Two calibration models were developed. The first model used a set of 42 standard mixtures of fructose, glucose, sucrose, and maltose prepared over the range of concentrations normally present in honey, whereas the second model used a set of 45 honey samples from various floral and regional sources. The developed models were validated with different data sets and verified by high-performance liquid chromatography (HPLC) measurements. The R (2) values between the FTIR-mATR predicted and HPLC results of the different sugars were between 0.971 and 0.993, demonstrating the predictive ability and accuracy of the procedure.

Carbohydrates↗

PubMed2004

Spectroscopic quantification of bacteria using artificial neural networks.

Fourier transform-infrared spectroscopy, in conjunction with artificial neural networks, has been used for identification and classification of selected foodborne pathogens. Five bacterial species (Enterococcus faecium, Salmonella Enteritidis, Bacillus cereus, Yersinia enterocolitica, Shigella boydii) and five Escherichia coli strains (O103, O55, O121, O30, O26) suspended in phosphate-buffered saline were enumerated to provide seven different concentrations ranging from 10(9) to 10(3) CFU/ ml. The trained artificial neural networks were then validated with an independent subset of samples and compared with the traditional plate count method. It was found that the concentration-based classification of the species was 100% correct and the strain-based classification was 90 to 100% accurate.

Bacillus cereus↗

PubMed2004

Inactivation of Staphylococcus aureus by pulsed UV-light sterilization.

Pulsed UV light is a novel technology to inactivate pathogenic and spoilage microorganisms in a short time. The efficacy of pulsed UV light (5.6 J/cm2 per pulse) for the inactivation of Staphylococcus aureus as suspended or agar seeded cells was investigated. A 12-, 24-, or 48-ml cell suspension in buffer was treated under pulsed UV light for up to 30 s, and 0.1 ml of sample was surface plated on Baird-Parker agar and incubated at 37 degrees C for 24 h to determine log reductions. Also, 0.1 ml of cell suspension in peptone water was surface plated on Baird-Parker agar plates, and the plates were treated under pulsed UV light for up to 30 s. The treated and untreated plates were incubated in the conditions described above. A 7- to 8-log CFU/ml reduction was observed for suspended and agar-seeded cells treated for 5 s or longer. In the case of suspended cells, the sample depth, time, treatment, and interaction were significant (P < 0.05). In the case of agar-seeded cells, the treatment time was significant (P < 0.05). Our results clearly indicate that pulsed UV technology has potential for the inactivation of pathogenic microorganisms.

Colony Count, Microbial↗

PubMed2003

Simultaneous monitoring of organic acids and sugars in fresh and processed apple juice by Fourier transform infrared-attenuated total reflection spectroscopy.

A combination of Fourier transform infrared spectroscopy (FT-IR) and chemometrics was used as a screening tool for the determination of sugars and organic acids such as sucrose, glucose, fructose, sorbitol, citric acid, and malic acid in processed commercial and extracted fresh apple juices. Prepared samples of synthetic apple juice in different constituent concentration ranges were scanned by attenuated total reflectance (ATR) accessory and the spectral region in the range between 950 and 1500 cm(-1) was selected for calibration model development using partial least squares (PLS) regression and principal component regression (PCR). The calibration models were successfully validated by high-performance liquid chromatography (HPLC) measurements against several commercial juice varieties as well as juice extracted from different apple varieties to provide an overall R2 correlation of 0.998. The present study demonstrates that Fourier transform infrared spectroscopy could be used for rapid and nondestructive determination of multiple constituents in commercial and fresh apple juices. Results indicate this approach to be a rapid and cost-effective tool for routine monitoring of multiple constituents in a fruit juice production facility.

Beverages↗

PubMed2002

Characterization of irradiated starches by using FT-Raman and FTIR spectroscopy.

Fourier transform infrared (FTIR) and Fourier transform Raman (FT-Raman) methods were used for rapid characterization and classification of selected irradiated starch samples. Biochemical changes due to irradiation were detected using the two vibrational spectroscopic techniques, and canonical variate analysis (CVA) was applied to the spectral data for discriminating starch samples based on the extent of irradiation. The O-H (3000-3600 cm(-1)) stretch, C-H (2800-3000 cm(-1)) stretch, the skeletal mode vibration of the glycosidic linkage (900-950 cm(-1)) in both Raman and infrared spectra, and the infrared band of water adsorbed in the amorphous parts of starches (1550-1750 cm(-1)) were employed in classification analysis of irradiated starches. Spectral data related to water adsorbed in the noncrystalline regions of starches provided a better classification of irradiated starches with 5 partial least-squares (PLS) factors in the multivariate model.

Carbohydrate Conformation↗

PubMed2002

Rapid determination of vitamin C by NIR, MIR and FT-Raman techniques.

Rapid spectroscopic determination of vitamin C in food and pharmaceutical products using infrared and Raman techniques was proposed. In this study, near-infrared (NIR), Fourier transform near-infrared (FT-NIR), Fourier transform infrared-attenuated total reflectance (FTIR-ATR), diffuse reflectance (DRIFTS), Fourier transform infrared-photoacoustic (FTIR-PAS) and FT-Raman spectroscopy were used in conjunction with partial least squares (PLS) regression to quantify vitamin C in powdered mixtures and solutions. Results indicate that the methods adopted have high prediction correlation. R2 values were 0.999 for FTIR-ATR, 0.976 for DRIFTS, 0.966 for FTIR-PAS, 0.988 for NIR, 0.992 for FT-NIR and 0.95 for FT-Raman, with an overall prediction error of 0.2-3.0%. The time required to complete an experiment ranged from 5 s (NIR) to 3 min (FT-Raman). The FTIR and FT-Raman techniques can be complementary tools for qualitative and quantitative characterization of the samples. Infrared and Raman techniques can be used to quantify vitamin C in foods and pharmaceutical products.

Ascorbic Acid↗