Dhananjay Bodas

Multiplexed Detection of Waterborne Pathogens in Circular Microfluidics

Microfluidic lab-on-a-chip presents an ideal solution for bacterial sensing and identification due to its advantages like large surface-to-volume ratio, requirement of low sample volume and multiplexing possibility. The present work deals with the development of an immunosensor chip using circular microchannels fabricated directly with microdimensional copper wire and permanent magnet for capture of Fe3O4 magnetic nanoparticle (MNP) conjugate. The MNP facilitate capture of the antigen in a confined space and hence, enhanced fluorescence signal for detection. The multiplexed microfluidic chip permits visual detection and quantification of waterborne pathogens viz. Escherichia coli and Salmonella typhimurium simultaneously. CdTe quantum dots (QDs) with different emission wavelengths were conjugated with anti-E. coli and anti-S. typhimurium antibodies for concurrent fluorescence detection. The present technique provides an inexpensive yet powerful tool to image and quantify pathogens at low numbers with passage of large sample volumes.

Lanthanum strontium manganese oxide (LSMO) nanoparticles: a versatile platform for anticancer therapy

Lanthanum Strontium Manganese oxide (LSMO) nanoparticles are a new class of magnetic nanoparticles which exhibit favorable magnetic and biological properties. These nanoparticles have opened avenues for multi-modal cancer therapy using hyperthermia, imaging, and diagnosis. Ease of synthesis and facile surface modification makes LSMO nanoparticles promising candidates for application in anti-cancer therapy.

Radio-frequency triggered heating and drug release using doxorubicin-loaded LSMO nanoparticles for bimodal treatment of breast cancer

Radio-frequency responsive nanomaterials combined with drugs for simultaneous hyperthermia and drug delivery are potential anti-cancer agents. In this study, chitosan coated La0.7Sr0.3MnO3 nanoparticles (C-LSMO NPs) were synthesized and characterized by X-ray diffraction, dynamic light scattering, Fourier transform infra red spectroscopy, vibrating sample magnetometer, scanning electron and atomic force microscopy. Under low radio-frequency (365kHz, RF), C-LSMO NPs (90nm) showed good colloidal stability (+22mV), superparamagnetic nature (15.4 emu/g) and heating capacity (57.4W/g SAR value). Chitosan facilitated doxorubicin entrapment (76%) resulted in DC-LSMO NPs that showed drug release upon a 5min RF exposure. MCF-7 and MDA-MB-231 cancer cells responded to a 5min RF exposure in the presence of bimodal DC-LSMO NPs with a significant decrease in viability to 73% and 88% (Pearson correlation, r=1, P<0.01) respectively, as compared to hyperthermia alone. Internalization of DC-LSMO NPs via the endosomal pathway led to an efficient localization of doxorubicin within the cell nucleus. The ensuing DNA damage, heat shock protein induction, and caspase production triggered apoptotic cell death. Moreover, DC-LSMO NPs successfully restricted the migration of metastatic MDA-MB-231 cancer cells. These data suggest that DC-LSMO NPs are potential bimodal therapeutic agents for cancer treatment and hold promise against disease recurrence and drug resistance.

Hydrothermal synthesis and characterization of carbon nanospheres: a mechanistic insight

Hydrothermally synthesized carbon nanospheres (CNS) follow a process of early nucleation followed by growth during synthesis. Here we report that growth occurs precisely after 5 min and prior to it nucleation occurs. The nucleation is a brief step in nanoparticle formation followed by growth of the nanoparticle depending on the reaction parameters.

Development of PVdF based pressure sensor for low pressure application

Development of poly(vinyl difluoride) (PVdF) based dynamic pressure sensor for low pressure application is reported in the present paper. β-phase PVdF film of thickness 10 µm is fabricated using spin casting method with thermally evaporated Al electrodes (200 nm) on both sides of the film. The film is polled and packaged in a poly(dimethyl siloxane) (PDMS) block. The exposed area of the pressure sensor is ∼500µm in diameter. A signal conditioning circuit is designed to amplify the signal and a NI DAQ card with LabVIEW software is used to acquire the signal on a PC. The dynamic pressure response of the sensor is recorded which shows linearity in detection. Pressure measured by the sensor is in the range of 10 to 150kPa.

Magnetically active micromixer assisted synthesis of drug nanocomplexes exhibiting strong bactericidal potential

In the ever-growing demand for drug nanocomplexes (DNCs), the need for smart systems or processes is indispensable to circumvent the demerits imposed by the conventional methods for the synthesis of DNCs. The demerits include prolonged hours of the synthesis, minimal loading and poor conjugation. Herein, we proposed a simplistic approach for the synthesis of DNCs through a magnetically active Polydimethylsiloxane micromixer which can render maximal loading in an unprecedented time. The UV-Vis, FTIR, and XRD analysis corroborate the proposed mechanism of conjugation of the drug and nanoparticles. The XPS, contact angle and zeta potential measurements revealed the composition, hydrophilicity and surface charges of the synthesized DNCs, respectively. Further, the microscopy images exemplify the encapsulation of the drug. In the antibacterial activity studies, the DNCs substantially inhibited the growth of the Staphylococcus aureus bacteria. FESEM images proved preferential accumulation of DNCs around bacterial cells effectively annihilating them

A high affinity phage-displayed peptide as a recognition probe for the detection of Salmonella Typhimurium

Salmonellosis is one of the most common and widely distributed foodborne diseases. A sensitive and robust detection method of Salmonella Typhimurium (S. Typhimurium) in food can critically prevent a disease outbreak. In this work, the use of phage displayed peptides was explored for the detection of S. Typhimurium. A phage-displayed random dodecapeptide library was subjected to biopanning against lipopolysaccharide (LPS) of S. Typhimurium. The peptide NFMESLPRLGMH (pep49) derived from biopanning displayed a high affinity (25.8nM) for the LPS of S. Typhimurium and low cross-reactivity with other strains of Salmonella and related Gram-negative bacteria. Molecular insights into the interaction of pep49 with the LPS of S. Typhimurium was gleaned using atomistic molecular dynamics simulations and docking. It was deduced that the specificity of pep49 with S. Typhimurium LPS originated from the interactions of pep49 with abequose that is found only in the O-antigen of S. Typhimurium. Further, pep49 was able to detect S. Typhimurium at a LOD of 10(3) CFU/mL using ELISA, and may be a potential cost efficient alternative to antibodies.

Benzophenone doped polydimethylsiloxane: self developable composite resist system for its use in a direct write laser lithography application

This paper reports a benzophenone doped polydimethylsiloxane (PDMS) composite resist system, for micro patterning using direct write laser lithography for its use in lab-on-chip (LOC) applications. A 248 nm excimer laser with a 20 ns pulse width is used for microfabrication of doped-PDMS. The effect of two major aspects viz. resist composition and laser processing parameters on the quality of fabricated microstructures is studied and optimized. The lithographic analysis reveals that the doped-PDMS shows self developable sensitivity at lower threshold fluence, 250 mJ cm−2. The optimized composition ratio 10: 1: 0.3 (wt%) of the PDMS monomer: curing agent: Benzophenone (P:C:B) is used for processing and analysis. Comprehensive analysis on the effect of laser ablation parameters (fluence, frequency and number of laser pulses) on etching performance (etch rate, geometry of micropattern and quality of surface) is presented. Increase in etch rate with fluence (250–650 mJ cm−2) is observed and considered to be in a working range. Simultaneously, increase in surface roughness as a function of fluence >650 mJ cm−2 is observed which can be associated with rapid rise in the photothermal decomposition of the composite resist. However pulse repetition rate (PRR) at 1, 5 and 10 Hz does not offer any significant effect on etch rate. The surface quality at a higher PRR is deprived due to redeposition of ablated material which concludes 1 Hz as a suitable working frequency. The deterioration of surface quality with increasing PRR is associated with the formation of a heat affected zone, due to cumulative heating, as the increase in temperature is 362 °C at 5 Hz and 624 °C at 10 Hz, above Ts ~ 1099 °C for 1 Hz. However, the number of pulses and etch rate are inversely related due to the plume effect. The overall study provides a guideline for precise control on fast prototyping direct write laser lithography processes used in LOC applications.

Development of a novel smartphone-based application for accurate and sensitive on-field hemoglobin measurement

Here, we report on the development of a smartphone-based application (app) for the accurate and sensitive measurement of hemoglobin (Hb). Hb values obtained using the app correlated significantly (R2 = 0.976) with those obtained by an automated hematology analyzer. Bland–Altman analysis showed that the standard deviation of the difference between Hb measured by the two methods was 0.35 g dL−1 and the limits of agreement between the two methods were −0.62 to 0.75. A limit of detection of 0.66 g dL−1 was achieved using the app along with a 2 g dL−1 limit of quantification. Furthermore, measurement using the app was highly sensitive (94%) and specific (90%). The app was developed for a smartphone and it will be particularly useful in resource-limited conditions for the rapid, accurate, highly sensitive and specific assessment of anemia.

Room temperature magnetism and metal to semiconducting transition in dilute Fe doped Sb1?xSex semiconducting alloy thin films

The magnetism was observed in very dilute Fe doped alloy thin film Fe0.008Sb1?xSex, for x?=?0.01 to 0.10. These thin films were grown on silicon substrate using thermal evaporation technique. Structural, electrical, optical, charge carrier concentration measurement, surface morphology and magnetic properties were observed using glancing incidence x-ray diffraction (GIXRD), four probe resistivity, photoluminescence, Hall measurement, atomic force microscopy (AFM) and magnetic force microscopy (MFM) techniques, respectively. No peaks of iron were seen in GIXRD. The resistivity results show that activation energy increases with increase in selenium (Se) concentration. The Arrhenius plot reveals metallic behavior below room temperature. The low temperature conduction is explained by variable range-hopping mechanism, which fits very well in the temperature range 150?300 K. The decrease in density of states has been observed with increasing selenium concentration (x?=?0.01 to 0.10). There is a metal-to-semiconductor phase transition observed above room temperature. This transition temperature is Se concentration dependent. The particle size distribution ?47?61 nm is evaluated using AFM images. These thin films exhibit ferromagnetic interactions at room temperature.