Muthu Manikandan

Platinum nanoparticles for the photothermal treatment of Neuro 2A cancer cells

This study demonstrates the effective synthesis of five different sized/shaped Pt NPs, within a narrow size regime of 1-21 nm using a modified methodology and the toxicity/biocompatibility of Pt NPs on Neuro 2A cancer cells was investigated elaborately by using light microscopic observations, tryphan blue exclusion assay, MTT assay and ICP-MS. The Pt NPs-C with sizes 5-6 nm showed superior non-cytotoxic property compared to the other four Pt NPs. These non-cytotoxic Pt NPs were employed for successful photothermal treatment of Neuro 2A cell lines using near-IR 1064 nm of laser irradiation. The Pt NPs-C could generate a 9 °C increase in temperature leading to effective photothermal killing of cancer cells. The MALDI-MS was used to prove the possibility of apoptosis related triggering of cell death in the presence of the Pt NPs. The results confirm that the current approach is an effective platform for in vivo treatment of neuro cancer cells.

Facile synthesis of gold nanohexagons on graphene templates in Raman spectroscopy for biosensing cancer and cancer stem cells.

Several surface enhanced Raman spectroscopy (SERS) substrates were prepared based on in situ nucleation of gold nanohexagons (Au) on graphene (G) nanosheets (Au@G), G, Au nanoparticles and Au conjugated G nanomaterials. These were applied to enhance Raman scattering and to differentiate human breast normal, cancer and cancer stem cells. These SERS substrates at concentrations of 100 µg/1 × 10(4) cells led to 5.4 fold increase in detecting breast cancer cells (BCCs) and 4.8 fold of sensitivity for detecting breast cancer stem cells (BCSCs) and they were able to identify and differentiate between normal cells, cancer cells and cancer stem cells. These approaches are rapid, simple and reliable for healthy normal cells, cancer cells and cancer stem cell detection which have a huge potential for cancer research for medical or biomedicine applications.

Bacterial toxicity/compatibility of platinum nanospheres, nanocuboids and nanoflowers

For the first time, we have investigated the bacterial toxicity or compatibility properties of Pt nanoparticles (NPs) with different sizes (P1, P2, P3, P4 and P5). The bacterio-toxic or compatible properties of these five different sized Pt NPs with the clinical pathogen, Pseudomonas aeruginosa were explored by many analytical methods such as the conventional plate count method, matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS), fluorescence microscopy and fluorescence sensoring techniques. The results revealed that the 1-3 nm sized (P1 and P2) Pt NPs showed bacterio-toxic properties while the 4-21 nm (P3, P4 and P5) Pt NPs exhibited bacterio-compatible properties. This is the first study which reports the bacterial toxicity of Pt NPs. The information released from this study is significantly important to future clinical, medical, biological and biomedical applications of Pt NPs.

Graphene nanoflakes as an efficient ionizing matrix for MALDI-MS based lipidomics of cancer cells and cancer stem cells

This study demonstrates that graphene nanoflakes can be efficiently used as a successful, interference free matrix for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The method is referred to as graphene-assisted laser desorption/ionization mass spectrometry (GALDI-MS), and it can be used for lipidomic analysis of cancer cells and cancer stem cells. The graphene nanoflakes were synthesized in-house and exhibited a transparent flake-like shape with characteristic crumpled silk waves in transmission electron microscopy and typical absorption characteristics upon UV-vis (λmax = 270 nm) and Fourier-transform infrared spectroscopic analysis. Graphene nanoflakes were tested as a sole matrix and co-matrix with traditional MALDI-MS matrices for the lipid extracts obtained from normal breast, cancer and cancer stem cells with four different spotting methods. In all the cases, the graphene nanoflakes displayed a noise free and good quality mass spectrum. This study reveals the possibility that lipids could self-assemble as a multi-layered structure on the graphene nanoflake platform by electrostatic interactions between the graphene nanoflakes and the lipid head groups and thus result in noise-free spectra from GALDI-MS based lipidomics.

Future perspective of nanoparticle interaction‐assisted laser desorption/ionization mass spectrometry for rapid, simple, direct and sensitive detection of microorganisms

The introduction of nanoparticles into mass spectrometric research greatly influenced the applicability of this technique into various omics. Surface-modified or functionalized nanoparticles (NPs) have recently extended the use of mass spectrometry into microorganism research. We survey the application of unmodified NPs, for microorganism research, on the basis of our expertise in this area within the recent years in this decade. The use of unmodified NPs in mass spectrometry, especially with respect to microorganisms, is an untreaded research area, which we have ventured to probe and have been fruitful. On the basis of our experience, we provide an insight into the principle behind the use of unmodified NPs and provide guidelines to be followed to obtain significant results. We also brief the current scenario of nanoparticle interaction-assisted laser desorption/ionization mass spectrometry (NPILDI-MS) for rapid, simple, direct and sensitive detection of microorganisms on the basis of our past and present reports, quoting examples of successful application of this technique. Finally, we address the future of the NPILDI-MS technique and the tools needed to reach those visions.

Rapid detection of haloarchaeal carotenoids via liquid-liquid microextraction enabled direct TLC MALDI-MS.

For the first time, we demonstrate the use of TiO2 nanoparticles (NPs) for enhancing the carotenoid production by the extremophilic haloarchea, Haloferax mediterranei. TiO2 NPs at optimal concentration of 375 mg/L results in a 95% increase in the production of carotenoid pigment compared to the control (no TiO2 NPs). The carotenoid pigments extracted from TiO2 NPs treated H. mediterranei cells, were separated using thin layer chromatography (TLC). The separated carotenoid spots were subjected directly for MALDI MS detection. To limit the sample diffusion during matrix addition on TLC plates, a simple bordering mode was exercised. Using this method we were able to detect the pigments successfully using MALDI-MS, directly from TLC plates after separation. In addition, we also applied the Pt NPs capped with ODT via Liquid-liquid microextraction (LLME) for extracting the pigment molecules from the halobacteria in MALDI-MS. These novel NP approaches possess numerous advantages such as; rapidity, ease in synthesis, high sensitivity and low cost.

A comparative study on the mode of interaction of different nanoparticles during MALDI-MS of bacterial cells

We propose the benefits of preincubation during nanoparticle-assisted bacterial analysis, where the bacteria are grown along with the nanoparticles. We were able to obtain a two to ten fold enhancement of bacterial signals in 3 h compared to the generally used methodology followed in previous literature. The previous literature method required a long time (18 h) to obtain such an enhancement. We probe the interactions of two bacteria, Staphylococcus aureus and Pseudomonas aeruginosa, with Ag, NiO, Pt TiO(2) and ZnO nanoparticles via transmission electron microscopy, ultraviolet spectroscopy and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS). Based on these results, we propose a mechanism for interaction of these five nanoparticles with bacteria. Two mechanisms were observed for the interactions: (1) Mechanism A is proposed for the Pt and NiO NPs which functioned based on affinity for bacterial cells. (2) Mechanism B was proposed for the bactericidal NPs such as TiO(2), ZnO and Ag NPs. The results indicate that the success of the unmodified NPs in MALDI-MS bacterial studies lies in following the ideal protocol for incubation at the ideal concentrations.

Cell population based mass spectrometry using platinum nanodots for algal and fungal studies

For the first time, we applied cell-population based mass spectrometry (CP-MS) for biosensing intact eukaryotic cells of Chlamydomonas reinhardtii and Saccharomyces cerevisiae. Cell counts ranging from 1 × 10(7) to 1.28 × 10(2) were analyzed using MALDI-MS to obtain the threshold detection sensitivity. Platinum nanodots (Pt NDs) were used to enhance the detection sensitivity of CP-MS. Pt NDs were able to improve the detection sensitivity of CP-MS from 3200 cells/mL to 640 cells/mL (5-fold) for Chlamydomonas. For yeast cells, the detection sensitivity was also increased from 400,000 cells/mL to 3200 cells/mL (125-fold) when Pt NDs were used. Using the Clin Pro tool, the obtained results from MALDI-MS data were validated. Statistical analysis of the mass data was performed using MYSTAT software.

Rapid and direct detection of attomole adenosine triphosphate (ATP) by MALDI-MS using rutile titania chips

We report the rutile titania-based capture of ATP and its application as a MALDI-MS target plate. This chip, when immersed in solutions containing different concentrations of ATP, can capture ATP and lead to its successful detection in MALDI-MS. We have optimized the ideal surface, showing an increased capture efficacy of the 900 °C (rutile) titania surfaces. We demonstrate the use of this chip as a target plate for direct analysis of the attached ATP using MALDI-MS, down to attomolar concentrations. This chip has a promising future for the detection of ATP in environmental samples, which may eventually be used as a pollution indicator in particular environments.

Low cost aluminium foil platforms for rapid mass spectrometric differentiation of the fungal pathogen Aspergillus niger mycelium and spores by in situ gold nanosphere accelerated microwave digestion

Fungal analysis involving filamentous pathogens is usually a challenging task. The present work uses aluminium foils as MALDI MS platforms for microwave digestion of whole fungal mycelium and spores belonging to the pathogen, A. niger. The 10 mm2 aluminium foil platforms cut from a 2 USD worth 80 m commercial foil pack, costs about 0.000008 USD per platform. The home made aluminium target holder on which we mount these foils costs only 100 USD, compared to the 600 USD of conventional stainless steel MALDI MS target plates. Hence a 6-times reduction in cost has been achieved using our system. Our results and optimization experiments concluded that a 3 min microwave digestion could lead to significant signals both in the case of mycelium and spores. The signals obtained were reliable and could help in the differentiation between the non-infecting mycelium and the highly infective and contagious sporulation phase. We further used the homemade Au nanospheres, known for their high heat absorption ability, for accelerating the microwave digestion on the Al foil platforms. The fungal analyte (mycelium/spores) when sandwiched between the Al foil on the ventral side and the Au nanospheres on the dorsal side led to significant reduction in the microwave time from 3 min to 30 s.