SINGH, MANJOT
(2020)
Study of biological interactions between water dispersed 2D-MoS2 nanosheets and live matter.
[Tesi di dottorato]
| Tipologia del documento: |
Tesi di dottorato
|
| Lingua: |
English |
| Titolo: |
Study of biological interactions between water dispersed 2D-MoS2 nanosheets and live matter |
| Autori: |
| Autore | Email |
|---|
| SINGH, MANJOT | manjot.singh@unina.it |
|
| Data: |
13 Marzo 2020 |
| Numero di pagine: |
233 |
| Istituzione: |
Università degli Studi di Napoli Federico II |
| Dipartimento: |
Fisica |
| Dottorato: |
Fisica |
| Ciclo di dottorato: |
32 |
| Coordinatore del Corso di dottorato: |
| nome | email |
|---|
| Capozziello, Salvatore | capozziello@unina.it |
|
| Tutor: |
| nome | email |
|---|
| Altucci, Carlo | [non definito] |
|
| Data: |
13 Marzo 2020 |
| Numero di pagine: |
233 |
| Parole chiave: |
2DMs, 2D TMDs, SEM, TEM, 2D-MoS2 |
| Settori scientifico-disciplinari del MIUR: |
Area 02 - Scienze fisiche > FIS/07 - Fisica applicata (a beni culturali, ambientali, biologia e medicina) |
[error in script]
[error in script]
| Depositato il: |
31 Mar 2020 16:07 |
| Ultima modifica: |
08 Nov 2021 12:01 |
| URI: |
http://www.fedoa.unina.it/id/eprint/13168 |
Abstract
The unique two dimensional structure and fascinating physicochemical properties of two dimensional materials (2D) have attracted tremendous attention worldwide in disease diagnosis and nano-biomedicine. As an analogue of 2D graphene, transition metal dichalcogenides (TMDs) such as 2D MoS2/WS2 nanosheets have been exploited as representative models in numerous applications ranging from nanoelectronics to the frontiers between nanomedicine and nanotechnology. The intriguing physical and chemical properties of 2D TMDs such as confinement in dimension due to their extreme thinness, stable free standing atomic crystal nanosheets without any substrate, unparalleled surface area to volume ratio, highly biocompatible and flexibility in functionalization with different biological molecules makes them potentially favorable candidate for many biomedical applications.
To get an insight into the biological and environmental fate of these engineered 2D nanosheets, it is very crucial to understand the nano-bio interactions at a prior level. Basically, the biological response to 2D nanomaterials is governed by material-specific behavior which further can be understood by the fundamental physicochemical properties of that material. Generally, three fundamental interaction modes are studied to analyze the biological impact of a given nanomaterial: a) chemical interactions, b) electronic and surface redox reactions and c) very unique physical and mechanical interactions. In general, 2DMs have shown wide range of behaviors with respect to these three modes of interactions at bio-nanosheet interface studies. Among these three modes, physical and mechanical interaction represents a unique way to study the biological response of 2D TMD nanosheets because of their high surface area to volume ratio, surface charge tuning and polarity. To exploit the full potential of 2D TMD nanosheets in biological applications, it is highly required that the given nanomaterial to be highly biocompatible, reproducible in the relevant physiological medium, flexibility in functionalization and with minimum cytotoxicity to the normal cells. In such a case and from the materials perspective, highly versatile, scalable, cost efficient and green fabrication techniques are required to obtain 2D nanosheets with the desired properties. To accomplish this aim, among various fabrication techniques reported for 2D TMDs such as chemical vapor deposition, electrochemical exfoliation, lithium intercalation, hydrothermal, sol-gel and liquid phase exfoliation, the latter one is the most versatile, scalable and cost effective technique for the production of few-layer nanosheets (1–10 stacked monolayers), with low monolayer content. Particularly in this technique, a careful optimization of exfoliation parameters such as, choice of green solvents, initial concentration of the solution, exfoliation time and controlled centrifugation for size and thickness selection of 2D nanosheets is very crucial to understand their environmental impact and behavior in biological media.
To this aim, my PhD project is focused on the noticeable progress on green and scalable production of MoS2 nanosheets in water as a pure solvent, having stability up to three weeks or more by carefully optimizing critical exfoliation parameters. Such a long stability time in water, which is a non-trivial result, is crucial to test the impact of 2DMs with biological live matter in its native context, as experiments aimed at these goals may take a few days or even longer to be completed. Thus, we stress that our innovative preparation of naked MoS2 nanosheets in water solvent represents an essential step ahead for an appropriate characterization of 2DMs – live matter interactions in its natural environment.
Till date, our group has investigated the biological interactions of bare MoS2 nanosheets with three different kinds of human cells, two tumoral, MCF7 (breast cancer) and U937 (leukemia), and one normal, HaCaT (epithelium), and two different kinds of Salmonella- ATCC 14028 and wild type S.typhimurium. It is worth noting that while MCF, and HaCaT cells have been already partly investigated with respect to their interactions with MoS2 nanosheets, U937-MoS2 interactions are completely unknown so far. Yet, MCF7 (Breast Cancer), Hela (Human Cervical Cancer), PC3 (Human Prostate Cancer), SMCC-7721 (Human Hepatocellular Carcinoma), B16 (Mouse Melanoma) and A549 (Human Lung Carcinoma) as cancer cell lines have been also recently tested as models by other research groups for the interactions between human cells and 2D functionalized nanomaterials of various composition, there including 2D Black Phosphorus nanosheets, 2D Boron nanosheets, 2D Antimonene quantum dots, 2D Antimonene nanosheets and Tin Sulfide nanosheets.
Here, we found a very interesting and novel result from our experiments: the impact of MoS2 nanoflakes was found to be quite different in normal from cancer cell lines. While the latter cells revealed a significant cytotoxic effect based on a very large increase of cell death, the former were essentially unaffected in this respect and only showed some mechanical damage when morphologically analyzed by SEM microscopy. This cytotoxic effect was also found to be dependent on the concentration and layer number of 2D nanoflakes. In the near future, this preliminary analysis might open up new routes for significant applications of MoS2 nanosheets as targeted anti-cancer systems. This analysis was further extended to bacteria and viruses. Particularly, we have investigated the mechanical interaction of 2D MoS2 nanoflakes with two different types of Salmonella typhimurium (ATCC 14028 and wild-type) which is a very serious Gram negative facultative anaerobe causing gastroenteritis in humans and in some cases it also results in serious neurological abnormalities with very high mortality rate. SEM analysis performed after the incubation of the complex system revealed significant damage to the bacterial morphology and leakage of intra-cellular components from the bacterial structure. Both of the salmonella types when treated with 2D MoS2 nanosheets, showed that the sharp edges of the nanoflakes can cut and/or damage bacterial membrane leading to an evident bactericidal effect.
Additionally, with a motive to deposit MoS2 nanosheets onto a patterned or machined substrate, particularly silicon because of its widely explored technological significance and usage in various laser processing techniques, we have first investigated the surface structuring of silicon using femtosecond laser pulses with a broad range of repetition rates (10 Hz – 200 kHz). Careful selection of various experimental conditions results in the formation of surface patterns which paves the way for numerous interesting applications. In view of this, I have introduced some preliminary results of LPE exfoliated MoS2 nanosheets deposited onto patterned silicon substrate for investigating non-linear optics of 2D nanosheets based on their thickness and given lateral size, in ongoing projects chapter at the end of this thesis.
Also, enthused from the synergistic impact of 2D MoS2 nanosheets on S. typhimurium, we are currently investigating the potential interaction of the same on two other types of bacteria such as Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). In this ongoing research, we have achieved a significant time and concentration dependent damage to bacterial morphology tested at different points. We have also extended our study to analyze the mechanical interaction of water exfoliated 2D MoS2 nanosheets on a very commonly effected contagious virus, Herpes Simplex Virus (HSV-1), which has shown a good percentage of virus inhibition treated with water exfoliated MoS2 nanosheets. In fact, further investigations are under study and some of the preliminary results have been added into the ongoing projects chapter of this thesis.
In order to understand the specific mechanism of action of 2D MoS2 nanosheets on the already tested tumor and normal human cells in this thesis, we have further extended our analysis in another ongoing project to go into deeper insights of 2D MoS2 nanosheets - live matter interaction using advanced Raman microscopy technique. The cell viability and the subsequent Raman microscopic analysis performed on the MoS2 nanosheets incubated with the similar human cell lines (MCF-7, U937 and HaCaT) revealed noteworthy results confirming the specific action of MoS2 nanosheets on tumor cell line (MCF-7 and U937), whereas very little or negligible effect on normal cell line (HaCaT).
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