Antibacterial Porous Polymeric Monolith for On-Chip Cell Lysis

The application of porous polymeric monolith (PPM) column as an e effective tool for bacterial cell lysis is demonstrated in this thesis. By exploiting the expansive surface area and controllable pore size inalienable to PPM, a double mechanism cell lysis technique was developed. The bacterial cell wall is mechanically sheared (mechanical-shear lysis) by flowing through the narrow porous medium of the PPM column, but it is also damaged and disintegrated by physical contact (contact-killing lysis) with the antibacterial polymeric biocide covering the porous surface. This leads to leakage of the intracellular contents. The antibacterial monolithic columns possess the aptitude to constrain the growth, kill and e efficiently lyse gram-negative and gram-positive bacterial cells. The developed antibacterial PPM columns can be potentially used in developing commercial macro-columns for cell lysis like the columns commercially available for DNA isolation. Also, they can be used within microfluidic channels for on-chip cell lysis at the heart of integrated sample preparation device. The developed cell lysis technique eff efficiently lysed numerous gram-negative and gram-positive bacterial species with no chemical or enzymatic reagents utilized, power consumption required, complicated design and fabrication processes. Also, the cell lysate containing the DNA released from bacterial cells after lysing with the developed antibacterial PPM columns is ready to be used by PCR with no further purification needed. Amplified DNA genes were detected by gel electrophoresis starting from small volume and cells concentration down to 10^2 CFU/ml. This makes it an attractive on-chip lysis device that can be used in sample preparation for bio-genetics and point-of-care diagnostics. The PPM columns were formed by photo-initiated free radical copolymerization of functional and cross-linker monomers with the assistance of porogenic solvents and photo-initiator. The porous network was synthesized directly inside a microfluidic channel fabricated in a cross-linked poly(methyl methacrylate) (X-PMMA) substrate by well-controlled, high-throughput, and time and cost e effective laser micromachining. The unreacted double bonds at the surface of X-PMMA provide covalent bonding for the formation of the monolith, thus contributing to the mechanical stability of the PPM within the microchannel and eliminating the need for surface treatment. Two functional monomers belong to two different antibacterial polymers families have been used to form two antibacterial PPM columns. A functional monomer, N-(tert-butyloxycarbonyl)aminoethyl methacrylate, belongs to SMAMPs antibacterial polymer family was used to form antibacterial PPM column, SMAMPs-PPM. To demonstrate that cells were lysed via a dual mechanism, the active (functional) monomer, N-(tert-butyloxycarbonyl)aminoethyl methacrylate (Boc-AEMA), was protected by a Boc group to first demonstrate mechanical shearing lysis alone. Once the protecting group was removed the PPM became antibacterial, leading to improved performance. Both lysis mechanisms were thus validated. Furthermore, the lysis efficiency of the PPM was improved by tuning their hydrophobic-hydrophilic balance and determining the optimal flow rate, at which the bacterial cell walls were sufficiently mechanically sheared through the porous medium of the column to disrupt the cell membrane by physical contact with the antibacterial polymeric biocide covering the pore surface. To further con rm and validate the dual lysis mechanism with different monomer, an antibacterial PPM, DADMAC-PPM, from a functional monomer that is one of quaternary ammonium compounds, diallyldimethylammonium chloride (DAMMAC), which is intrinsically cationic and antibacterial, was developed. Also the e effect of the cross-linking monomer on bacterial growth inhibition, lysis efficiency and the mechanical stability of the PPM column within the microfluidic channel, using three different cross-linking monomers was studied. Moreover, the bonding e efficiency between two layers of X-PMMA substrate at different cross-linker contents was studied. Furthermore, the reusability of the QAC-PPM was investigated and compared with the previously developed SMAMPs-PPM. The cell lysis e efficiency of the biochips were characterized by qualitatively (semi-quantitatively) detecting DNA and quantitatively determining DNA concentration in the crude lysate collected at the outlet of the biochip. By using fluorometry, the ethidium bromide (EtBr) intercalation assay was utilized as an indicator of the presence of DNA in the cell lysate and the DNA concentration was determined by UV-Vis spectrophotometry. Furthermore, lysis was con rmed by o -chip PCR that was further analyzed by gel electrophoresis. The antibacterial PPM columns were reused for 20-30 lysis cycles without any evidence of physical damage to the monolith, significant performance degradation or DNA carryover when they were back-flushed between cycles

On-chip cell lysis by antibacterial non-leaching reusable quaternary ammonium monolithic column

Reusable antibacterial non-leaching monolithic columns polymerized in microfluidic channels designed for on-chip cell lysis applications were obtained by the photoinitiated free radical copolymerization of diallyldimethylammonium chloride (DADMAC) and ethylene glycol diacrylate (EGDA) in the presence of a porogenic solvent. The microfluidic channels were fabricated in cross-linked poly(methyl methacrylate) (X-PMMA) substrates by laser micromachining. The monolithic columns have the ability to inhibit the growth of, kill and efficiently lyse gram-positive Micrococcus luteus (Schroeter) (ATCC 4698) and Kocuria rosea (ATCC 186), and gram-negative bacteria Pseudomonas putida (ATCC 12633) and Escherichia coli (ATCC 35218) by mechanically shearing the bacterial membrane when forcing the cells to pass through the narrow pores of the monolithic column, and simultaneously disintegrating the cell membrane by physical contact with the antibacterial surface of the column. Cell lysis was confirmed by off-chip PCR without the need for further purification. The influence of the cross-linking monomer on bacterial growth inhibition, leaching, lysis efficiency of the monolithic column and its mechanical stability within the microfluidic channel were investigated and analyzed for three different cross-linking monomers: ethylene glycol dimethacrylate (EGDA), ethylene glycol dimethacrylate (EGDMA) and 1,6-hexanediol dimethacrylate (1,6-HDDMA). Furthermore, the bonding efficiency of two X-PMMA substrates with different cross-linking levels was studied. The monolithic columns were shown to be stable, non-leaching, and reusable for over 30 lysis cycles without significant performance degradation or DNA carryover when they were back-flushed between lysis cycles

Antibacterial Porous Polymeric Monolith Columns with Amphiphilic and Polycationic Character on Cross-linked PMMA Substrates for Cell Lysis Applications

The application of porous polymeric monolith (PPM) columns as an effective tool for bacterial cell lysi within microfluidic chips is demonstrated. By taking advantage of the large surface area and controllable pore size inherent to PPMs, we developed a double mechanism cell lysis technique. The bacterial cell wall is mechanically sheared by flowing through the porous medium of the PPM column, but it is also damaged and disintegrated by physical contact with the antibacterial polymeric biocide covering the porous surface. This leads to leakage of the intracellular contents. The stable and nonleaching antibacterial column introduced in this work alleviates the need for chemical or enzymatic lysins and their potential release of polymerase chain reaction (PCR) inhibitors. The PPM columns were obtained by the photoinitiated free radical co polymerization of n-butyl methacrylate (BuMA) and N-(tert butyloxycarbonyl)aminoethyl methacrylate (Boc-AEMA) in the presence of a cross-linker and porogenic solvents. The porous network was synthesized directly inside a microfluidic channel fabricated in a cross-linked poly(methyl methacrylate) (X-PMMA) substrate by laser micromachining. After removing the Boc protecting group with phosphoric acid, an amphiphilic and cationic network structure reminiscent of synthetic mimics of antimicrobial peptides (SMAMPs) was obtained. The antibacterial activity of the PPM columns was tested against Bacillus subtilis (B. subtilis) and Escherichia coli (E. coli) cells. Cell lysis was evidenced by DNA release, which was then amplified by PCR and confirmed by gel electrophoresis, to verify that the antibacterial monolithic columns did not strongly interfere with the PCR process

ZnO hollow spheres arrayed molecularly-printed-polymer based selective electrochemical sensor for methyl-parathion pesticide detection

A highly sensitive electrochemical-based detector was fabricated to selectively sense methyl-parathion (MP). A Glassy carbon electrode (GCE) was functionalized with zinc oxide (ZnO) hollow spheres (ZnOHS) and a molecularly imprinted polymer (MIP) to form the developed sensor. Cyclic voltammetry (CV) was performed to synthesize a molecularly imprinted polymeric film on the ZnOHS modified GCE (GCE/ZnOHS) by electropolymerization of functional monomer, l-arginine (L-Arg), and template molecule, MP. The differential pulse voltammetry (DPV) was utilized to evaluate the efficiency of the electrochemical detection of MP under optimal conditions by the proposed sensor. The developed sensor recorded a good performance for detecting MP in the linear range of 5 × 10−9 to 0.1 × 10−4 mol L−1 (R2=0.985) with a detection limit (S/N = 3) of 0.5 × 10−9 mol L−1 and sensitivity of 571 nA/μmolL −1 cm −2. This electrochemical sensing system effectively detects MP in real samples with satisfactory recoveries of 90.4%, 91.9%, 118%, and 96.3% for fresh green beans, strawberry, tomato, and cabbage, respectively. © 2021 Elsevier B.V.1

Synthesis and Characterization of a Mixed Nanofertilizer Influencing the Nutrient Use Efficiency, Productivity, and Nutritive Value of Tomato Fruits

Due to the higher potential for enhancing nutrient use efficiency, nanofertilizer (NF) is crucial in sustainable crop production. Thus, foliar-applied mixed nanofertilizer (MNFf) and commercial fertilizer (CF) into the soil (CFs) were claimed together ([MNFf + CFs]) and comparative nutrient use efficiency (NUE), productivity, and nutritional properties of tomato fruits were investigated. The mixed nanofertilizer (MNF) was prepared in our laboratory and characterized using scanning electron microscopy, X-ray diffraction, and Fourier transform infrared. To avoid the interference of other factors, all the treatments were divided into three groups: (i) blank treatment (no fertilizer), (ii) CF treatment, and (iii) combined [MNFf + CFs] treatment. The vegetative growth and qualitative and quantitative attributes of tomatoes were recorded, and the NUE, total production, and benefit-cost ratio (BCR) were also calculated. In addition, comparative nutritional properties for all treatments were analyzed. The plant's height, stem diameter, root length, photosynthetic pigments, leaf minerals, and qualitative traits of tomato fruits were significantly (p < 0.05) increased by [MNFf + CFs] treatment compared to CFs. The protein, fiber, Fe, Zn, and K contents were significantly (p < 0.05) increased by 23.80, 38.10, 44.23, 60.01, and 2.39%, respectively, with the [MNFf + CFs] treatment as compared to CFs, while the ash and protein contents were both lower than the untreated tomato. Moreover, [MNFf + CFs] treatment has significantly (p < 0.05) increased the antioxidant properties. The NUE, total production, and BCR were also increased by 26.08, 26.04, and 25.38%, respectively, with the same treatment. Thus, [MNFf + CFs] treatment could be a potential alternative for reducing the excess use of CF. © 2021 The Authors. Published by American Chemical Society.1

Does Weight Loss Through Means of Bariatric Surgery Reduce the Risk of Type 2 Diabetes in Obese Qatari Patients: A retrospective analysis

Background and objectives: The use of bariatric surgeries such as Gastric Bypass and Sleeve Gastrectomy in managing obesity and associated diseases such as type 2 diabetes mellitus (T2DM) has been induced in clinical practice. Weight reduction through means of bariatric surgery has metabolic benefits and may improve the management of T2DM. The aim of this study was to investigate if weight loss through bariatric surgery can reduce the risk of T2DM in patients without the onset of T2DM. Study design: A retrospective analysis was conducted on post-bariatric patients at the department of bariatric and metabolic surgery at Hamad General Hospital. Methods: Tow hundred and two eligible pre-diabetic Qatari patients who have undergone bariatric surgery in 2016 and satisfied the inclusion and exclusion criteria of the study were analyzed. Data on Glucose, Insulin and C-peptides levels at baseline and follow-up were extracted in order to compare the change of these variables at baseline, 6 and 10 months follow up before and after 10 months from the date of surgery. Results: Seventy one males with mean age of 32.73 ± 10.37 and one hundred and thirty one females with mean age of 33.90 ± 9.88 were included in the analysis. Change in weight was strongly and positively associated with change in insulin level (0.701, 95% CI: 0.027, 1.347, p= 0.042) also, as weight changes fasting glucose changes (1.993, 95% CI: 0.359, 3.627, p= 0.017). Follow-up period greater than 6 months was not found to be significantly associated with weight loss (2.049, 95% CI: -2.249, 6.349, p= 0.313). Conclusion: Our study confirms results from international studies that weight loss through bariatric surgery can reduce the risk of developing Type 2 Diabetes in Qatari obese patients. The results of the study also suggest that post-surgery periods can be detrimental to the fate of fasting glucose and insulin levels and therefore compliance maybe of great importance to ensure success and sustainability of weight loss and diabetes prevention. Larger samples size and longer follow-up period is required to confirm these findings.Qatar University and Hamad Medical Corporatio

Application of Stabilized Cefixime-AgNPs-GO Thin Films as Corrosion Inhibitors for Mild Steel Alloy

In this work, the corrosion inhibition of mild steel at ambient conditions by an antibiotic in a solution that contains silver nanoparticles (AgNPs) and graphene oxide (GO) was studied. GO and AGNPs were prepared by one-step simple and ecofriendly method and characterized by different techniques. Different concentrations of the inhibitor were prepared and their inhibition efficiency in acidic media was investigated. The adsorption characteristics of the inhibitor were studied and it was found that the antibiotic (Cefixime) alone and with GO combined with AgNPs inhibit the corrosion of mild steel by being adsorbed on the surface of mild steel by a physical adsorption mechanism. The adsorption of Cefixime and GO with AgNPs on the mild steel surface was found to be spontaneous. Incorporating AgNPs and GO with Cefixime showed an additional inhibition efficiency when compared with using only Cefixime. This indicates the strong inhibition efficiency offered by incorporating the antibiotic with AgNPs and GO

Association of the serum chemerin level with the development of diabetic retinopathy in patients with type 1 diabetes mellitus

Background: In patients with type 2 diabetes mellitus, the development of diabetic retinopathy (DR) correlates positively with elevated serum chemerin levels. This study was aimed at investigating the probable association between the serum chemerin level and the development of DR in patients with type 1 diabetes mellitus (T1DM). Methods: In this cross-sectional study, we included Egyptians and classified them into four groups: group 1, including healthy individuals; group 2, including patients with T1DM without DR; group 3, including patients with T1DM with non-proliferative DR (NPDR); and group 4, including patients with T1DM with proliferative DR (PDR). The assessment included best-corrected distance visual acuity assessment, slit-lamp biomicroscopy, funduscopy, fundus fluorescein angiography, and macular ocular coherence tomography. Fasting blood samples were obtained from all participants to measure serum chemerin, glycated hemoglobin (HbA1c), total cholesterol, triglyceride, and creatinine levels. Serum chemerin levels were compared among the groups, and their correlations with age, duration of diabetes, HbA1c, total cholesterol, triglyceride, and creatinine levels were analyzed. Results: We recruited 209 participants, including 46 healthy individuals in group 1, 52 patients (T1DM and no DR) in group 2, 61 patients (T1DM and NPDR) in group 3, and 50 patients (T1DM and PDR) in group 4, with comparable mean ages and sex ratios among groups. The diabetes duration, body mass index, HbA1c, total cholesterol, triglyceride, and serum chemerin levels differed significantly among the groups (all P < 0.001), whereas the creatinine level did not (P > 0.05). The serum chemerin level was significantly higher in group 4 than in groups 3 and 2, in group 3 than in group 2, and in groups 3 and 4 than in group 1 (all P < 0.001). However, it was comparable between groups 1 and 2 (P > 0.05). It correlated with the duration of T1DM and HbA1c, total cholesterol, triglyceride, and creatinine levels but not with age. Conclusions: Patients with T1DM with DR showed higher serum chemerin levels than those with T1DM without DR or healthy individuals. Serum chemerin levels were higher in those with PDR than in those with NPDR. Thus, serum chemerin levels are a potential biomarker of the development and severity of DR in patients with T1DM. Nevertheless, future diagnostic accuracy studies are required to confirm these potential applications