Hani Nasser Abdelhamid

Multifunctional graphene magnetic nanosheet decorated with chitosan for highly sensitive detection of pathogenic bacteria

Multifunctional graphene magnetic nanosheet decorated with chitosan (GMCS) is demonstrated as a promising biosensor for fluorescence spectroscopy and it can be also applied for matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) for sensitive pathogenic bacteria detection. Graphene-magnetic@chitosan (GMCS) can be applied for multiple applications such as fluorescence biosensor, fluorescence background suppressor, acting as co-matrix, enriching nanoprobe, and separation by external magnets for pathogenic bacteria (Pseudomonas aeruginosa and Staphylococcus aureus) present in aqueous suspension or blood colloids. GMCS has been prepared and characterized using various techniques including TEM, UV, FTIR, XRD, Raman and fluorescence spectroscopy. Due to the non-covalent interactions among the pathogenic bacteria with the GMCS, fluorescence enhancement takes place as a function of bacterial cell number with a low number of cell detection (4.5 × 102 to 5.0 × 102 cfu mL-1) and wide linear dynamic range which indicates that the GMCS approach is an excellent quantitative methodology and highly sensitive approach for detection of bacteria cells. Graphene works intrinsically as a fluorescence quencher for blood fluorophores and cell autofluorescence as graphene typically has a long life time, which allows detection of the bacteria signals by direct fluorescence measurements. Because of the high fluorescence enhancement efficiency, and large surface area (to volume ratio) of graphene, GMCS exhibits extraordinarily high sensitivity for complex (blood) sample analysis. GMCS also can be applied as an efficient separation and preconcentration nanoprobe for surface assisted laser desorption/ionization (SALDI) and enhances the ionization of bacterial biomolecules during MALDI-MS analysis. The bacterial cell suspension was concentrated from 1 mL to 10 μL via an external magnetic field, thus it can enhance bacteria detection for MALDI-MS analysis. GMCS is an outstanding approach which is a rapid, sensitive, culture free technique and low cost biosensor for pathogenic bacteria detection.

Quantum dot applications endowing novelty to analytical proteomics.

This review surveys all the state‐of‐art applications of quantum dots (QDs) in conventional and modern analytical methods in proteomic studies. A brief introduction of QDs and their properties is initially presented followed by outlining the application of QDs in fluorescence, MS, imaging, and cancer‐based proteomics. The in‐depth application of QDs in MALDI‐MS and surface assisted laser desorption/ionization‐MS has been elaborately discussed, summarizing the speculated mechanism behind the protein–QDs interactions during QD matrix applications leading to enhanced detection sensitivity.

A method to detect metal-drug complexes and their interactions with pathogenic bacteria via graphene nanosheet assist laser desorption/ionization mass spectrometry and biosensors.

A new method was proposed to probe the interactions between transition metals of Fe(II), Fe(III), Cu(II) with a non steroidal anti-inflammatory drug (NSAID), flufenamic acid (FF) using graphene as a matrix for Graphene assisted laser desorption ionization mass spectrometry (GALDI-MS). Metal-drug complexation was confirmed via UV absorption spectroscopy, fluorescence spectroscopy, pH meter, and change in solution conductivity. The optimal molar ratios for these complexation interactions are stoichiometry 1:2 in both Cu(II) and Fe(II) complexes, and 1:3 in Fe(III) complexes at physiological pH (7.4). Metal complexation of the drug could enhance fluorescence for 20 fold which is due to the charge transfer reaction or increase rigidity of the drug. The main interaction between graphene and flufenamic acid is the П-П interaction which allows us to probe the metal-drug complexation. The GALDI-MS could sensitively detect the drug at m/z 281.0 Da (protonated molecule) with detection limit 2.5 pmol (1.0 μM) and complexation at m/z 661.0, 654.0 and 933.0 Da corresponding to [Cu(II)(FF)(2)(H(2)O)(2)+H](+), [Fe(II)(FF)(2)(H(2)O)(2)+H](+) and [Fe(III) (FF)(3)(H(2)O)(2)+H](+), respectively (with limit of detection (LOD) 2.0 pmol (10.0 μM). Matrix assisted laser desorption ionization mass spectrometry (MALDI-MS) spectra show change in the protein profile of intact pathogenic bacteria (Pseudomonas aeroginosa, Staphylococcus aureus). The change in the ionization ability (mainly proton affinity) of pathogenic bacteria may be due to the interactions between the bacteria with the drug (or its complexes). Shielding carboxylic group by metals and increase the hydrophilicity could enhance the biocompatibility of complexes toward the pathogenic bacteria which can be used as biosensors with high sensitivity and lowest detectable concentrations are in the range of 3.3×10(3)-3.9×10(4) cfu mL(-1) with large linear dynamic range.

Near infrared (NIR) laser mediated surface activation of graphene oxide nanoflakes for efficient antibacterial, antifungal and wound healing treatment.

Photothermal treatment of graphene oxide (GO) for antibacterial, antifungal and controlling the wound infection treatment using near infrared laser (NIR, Nd-YAG (λ=1064 nm) were reported. Various pathogenic bacteria (Pseudomonas aeruginosa, Staphylococcus aureus) and fungi (Saccharomyces cerevisiae and Candida utilis) were investigated. The cytotoxicity was measured using the proteomic analysis by matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS), optical density (OD600), standard microdilution procedures, transmission electron microscopy (TEM) and epifluorescence microscopy. The laser mediated the surface activation of GO offer high efficiency for antifungal and antibacterial. Wide broad cells with various instruments approved that graphene oxide is promising material for nanomedicine in the near future.

Chitosan nanomagnets for effective extraction and sensitive mass spectrometric detection of pathogenic bacterial endotoxin from human urine

Direct analysis and profiling of a complex endotoxin without any prior purification or sample treatment techniques using chitosan nanomagnets coupled with MALDI-MS techniques has been demonstrated. Surface modified magnetic nanoparticles such as Fe3O4 and CuFeO2 with chitosan were synthesized and characterized by using UV, TEM, and FTIR. Endotoxin (lipopolysaccharides (LPS)) was spiked into human urine and recovery enabled using chitosan nanomagnets. For the first time, the use of CuFeO2@chitosan and Fe3O4@chitosan nanomagnets for affinity based separation and enrichment of trace levels of endotoxin and direct detection using MALDI-MS has been successfully achieved. The chitosan nanomagnet based recovery of endotoxin from urine samples showed a high degree of sensitivity compared to the conventional MALDI-MS analysis, where the lowest detectable endotoxin concentration was 30 mg mL-1 (0.15 mg, 5 μL). The Fe3O4@chitosan nanomagnet approach has 67 times higher sensitivity at 450 μg mL-1 (2.25 μg, 5 μL) compared to the direct MALDI-MS analysis. However, CuFeO2@chitosan nanomagnets appeared to be more effective than Fe3O4@chitosan nanomagnets (about 4 times) and 250 times more sensitive for separation at 120 μg mL-1 (0.6 μg, 5 μL) and detection of endotoxin from urine. The current approach proposes a novel MALDI-MS platform using the chitosan nanomagnets for extraction/detection of endotoxin from clinical samples such as human urine which can be further applied for biomedicine/clinical application for rapid, sensitive, direct and effective detection for bacterial infections.

Synthesis and application of ionic liquid matrices (ILMs) for effective pathogenic bacteria analysis in matrix assisted laser desorption/ionization (MALDI-MS)

Application of two new series of ionic liquid matrices (ILMs) based on the two most predominantly used conventional organic matrices (Sinapinic acid and 2,5-DHB) in conjugation with various bases (aniline (ANI), dimethyl aniline (DMANI), diethylamine (DEA), dicyclohexylamine (DCHA), pyridine (Pyr), 2-picoline(2-P), 3-picoline(3-P)) for bacterial analysis in matrix assisted laser desorption/ionisation mass spectrometry (MALDI-MS) are reported. The results reveal that ionic liquid matrices could significantly enhance the protein signals, reduce spot-to-spot variation and increase spot homogeneity. More importantly, these novel matrices would not produce any interference during MALDI-MS analysis. Among these ILMs, 2,5-DHB/ANI, 2,5-DHB/DMANI and 2,5-DHB/Pyr can be successfully applied to intact bacterial studies compared with other ILMs. Base molecules when added to conventional matrix can promote proton transfer between the bacterial lysate and the matrices. Due to the enhanced proton transfer efficiency by the ionic liquid matrices, almost all the biomolecules of the intact bacterial cells can be ionized and detected in the MALDI-MS. All synthesized ILMs were characterized using ESI (+)/MS and UV-spectroscopy.

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.

Probing the interactions of chitosan capped CdS quantum dots with pathogenic bacteria and their biosensing application

Chitosan modified CdS quantum dots (CdS@CTS) can be used as an effective bacterial biosensor due to their good bioaffinity among chitosan molecules and bacterial membranes. CdS@CTS is an ultrafast, sensitive, direct and biocompatible biosensor for pathogenic bacteria (Pseudomonas aeruginosa and Staphylococcus aureus). Chitosan biopolymer of CdS@CTS provides bioaffinity sites that can be employed for the assembly on pathogen bacteria cells due to the chemical similarity of the chitosan and the bacteria membranes. Thus, S. aureus and P. aeruginosa cells were detected at low concentrations of 150 and 200 cfu mL-1, respectively, in an extremely short time (1 min). The CdS@CTS-bacteria interaction is noncovalent. From the thermodynamic results, the van der Waals force and hydrogen bonding formation are characterized by negative enthalpy (ΔH), while positive entropy (ΔS) is considered as the evidence for typical hydrophobic interactions. Moreover, negative ΔH and positive ΔS might play a role in the electrostatic interactions. The negative free energy (ΔG) shows that the binding events were spontaneous processes. Matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) and transmission electron microscopy (TEM) were performed to evaluate the interactions and the biocompatibility of CdS@CTS toward bacteria cells. Their biocompatibility, together with the high sensitivity and the presence of multifunctional forces, making these quantum dots (CdS@CTS) an excellent and novel biosensor which can be widely applied in the near future.

Synthesis and antibacterial activities of graphene decorated with stannous dioxide

We report the synthesis and antibacterial activity of water dispersible stannous dioxide (SnO2) modified with graphene (G) nanosheets. Nanomaterials of G and SnO2@G were prepared and then characterized by transmission electron microscopy (TEM), ultraviolet (UV) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Raman and fluorescence spectroscopy. The antibacterial activities were investigated using Pseudomonas aeruginosa and Staphylococcus aureus as model strains of Gram negative and Gram positive bacteria, respectively. The antibacterial activities were evaluated using optical density (OD600) and plate counting methods. The results indicated that SnO2@G displayed a higher cytotoxicity than G by 1–3 fold. The G-based nanomaterials inhibited the growth of P. aeruginosa more effectively than for S. aureus. SnO2 increased the cytotoxicity of G against Gram negative bacteria by 3.6 times due to the synergic effect. The interactions between the prepared nanomaterials and bacteria cells were evaluated using TEM, fluorescence spectroscopy and matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS). The data revealed that there were many forces facilitating the SnO2@G nanosheets to adhere to bacteria cells, which block the cells from taking nutrients, and result in cell death. We expect that this novel G-based composite can be effectively applied in the future for environmental and clinical applications.

Graphene oxide as a nanocarrier for gramicidin (GOGD) for high antibacterial performance

As a powerful and novel nanocarrier, graphene oxide (GO) is employed to load a water insoluble antibacterial drug, gramicidin (GD), for effective antibacterial treatments. The loaded amount of GD on the surface of GO was calculated and was found to be 14% (wt%). The antibacterial activity of GO modified GD (GOGD) was measured against Pseudomonas aeruginosa and Staphylococcus aureus using plate counting, optical density (OD600), transmission electron microscopy (TEM), fluorescence (2D, 3D) and matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS). The use of multiple analytical approaches adds certainty to the cytotoxicity assessments of GOGD, which shows better efficiency than GO and GD. GOGD has potential wide-ranging effects against different bacterial strains. Nano-cytotoxicity mechanism was discussed in detail, and controversies in earlier results were refuted.