Special thanks to Dr Patience Mthunzi-Kufa for her supervision, guidance and creating opportunities for the success of the project. The WHO also reports that South Africa has the largest budget for antiretroviral treatment (ART) in the world, making the country a top consumer of the medication. Raman microscopy was used to assess the surface of the chemical sensors prior to application to the analytes.
Literature Review
Introduction
Most research in nanomaterial-based pharmaceutical investigations uses electrical and optical detection methods for signal collection [13-14]. Optical detection is also a key feature of this publication where photonics-based methods are explored in relation to pharmaceutical research. Second, a discussion is given on electrical and optical detection methods based on parameters such as limit of detection, linear range and sensitivity.
Nanomaterial scaffolds and therapeutic drug applications
- Polymeric nanomaterials and their applications
- Metallic nanomaterials and their applications
- Graphene based nano-sensors and applications
The nanoparticles in the above image have been used in various applications related to therapeutic drugs and drug delivery [33-35]. In the past decade, the fabrication of sensors and biosensors has been improved by the incorporation of graphene as a scaffolding material. Second, GO functionalized with platinum nanoparticles was investigated as a chemical sensor for glucose at concentrations in the.
Detection methods and sensing techniques
- Electrical detection methods
- Optical detection methods
Nanomaterials carry the property of surface plasmons which help in the detection method of the techniques [104]. Since the refractive index is related to the surface of the substrate, changes in the refractive index can also be correlated with binding affinities and used in medical diagnostics, drug detection and virus monitoring, among other applications [105]. In the second step, lectins are used as biorecognition elements for the detection of glycans.
Prospects and Shortcomings
In situ self-assembly of gold nanoparticles on hydrophilic and hydrophobic substrates for influenza virus sensing platform. In Vitro Administration of Gold Nanoparticles Functionalized with MUC-1 Protein Fragment Generates Cancer Vaccine Response via Macrophage Activation and Polarization Mechanism. Simultaneous electrochemical detection of dopamine and ascorbic acid using an iron oxide/reduced graphene oxide modified glassy carbon electrode.
Methodology
- Thin layer coating using Physical Vapor Deposition (PVD)
- Metallic nanoparticles for surface enhancement
- Citrate (Cit) crosslinking metallic nanoparticles of gold and silver on coated slides
- Cysteamine (Cys) crosslinking metallic nanoparticles of gold and silver on coated slides
- UV-Vis spectroscopy of metallic nanoparticles
- Characterization of functionalized MNPs using Transmission Electron Microscopy
- SERS analysis of ARVs on functionalized chemical sensors
- Statistical evaluation of ARVs using SERS
In the table above, four metals were chosen to make the first layers of chemical sensors. 10 µL of analytes were pipetted onto sample holders as follows: blank solution (water), reference solutions (crosslinker 1 and 2), MNP 1, MNP 2. A linear equation was derived from the graph along with R2 values that were used to determine the quality of the fit.
Results
UV-Vis spectroscopy of gold and silver nanoparticles
Transmission Electron Microscopy of gold and silver nanoparticles
58 due to changes in chemical functionality was not clear in these data, but Raman spectroscopy experiments will provide a detailed report on the molecular properties of the nanoparticles [5]. In the next section, samples were tested using TEM for further characterization prior to Raman microscopy. 59 in size distribution than Ag@Cit with its largest size at 40 nm with less than 15% frequency, while the latter contained particles of 45–50 nm in size with more than 10% frequency.
In Figure 3.3 above, gold and silver nanoparticles are depicted with their first size distribution as the histogram on the right. For Au@Cys, the nanoparticles show a spherical to oval shape and a size distribution of 5 to 40 nm dominated by 25 nm particles with a frequency of 17%. On average, the Au@Cys distribution is smaller than that of citrate with the largest frequency contribution of less than 18% compared to 22% of citrate.
Again, with silver nanoparticles, the largest size reached was 50 nm with 45 nm yielding over 12% of the frequency. In addition, the gold-based nanoparticles do not appear to have any contribution from particle sizes above 40 nm using either cross-linker, this observation is consistent with larger UV-Vis absorption bands found on silver samples compared to gold. The explanation for these results may be due to a higher yield of nanoparticles from silver, supported by the metal's broad UV band, which according to Beer Lambart's law is dependent on concentration.[12-14].
Due to the difference in particle size, a consistent evaluation of the nanoparticles in the laser.
Raman microscopy of fabricated chemical sensors
- Citrate/Gold and Citrate/Silver
- Cysteamine/Gold and Cysteamine/Silver
The red shift seen on the hydroxyl peak implies hydrogen bonding with the metal surface via the oxygen of the citrate and the hydrogen of the analyte. This redshift is a consequence of the layer increase, which allows more interaction between the crosslinker and the metal [22]. A similar redshift observation was made at 1400 cm-1 region where the strong stretching of the carboxylate exists.
First, the 1580 cm-1 band caused by the deformation of the functional group was shifted to the 100 nm layer, implying bond shortening due to the intermolecular interaction with the metal [23]. Similarly, the hydroxyl stretching mode remained blue-shifted at 50 nm in the 3200 cm-1 regions while the 20 and 100 nm cm-1 layers were red-shifted; the mixed response is unclear in terms of molecular interactions. Images of the 25 nm sample show a coating layer with spherical components and debris reflected from the gold surface.
The averaged spectra of the three samples were evaluated in terms of spectral content and molecular binding shifts. 68 900 and 1000 cm-1 where the 25 nm layer caused a blue shift while the thicker layers moved in the red direction of the spectrum. At the end of the spectra, the aliphatic and amine bonds are observed in the 3000 cm -1 regions [24].
Towards the end of the spectrum, the aliphatic bonds in the stretching mode in a mixture of Raman peak shifts while the thiol appeared red-shifted by 50 and 100 nm at 2500 cm-1.
SERS analysis of APIs on citrate-based chemical sensors
- Tenofovir on citrate based chemical sensors
- Statistical analysis of Tenofovir on glass, gold, and silver chemical sensors
- Lamivudine on citrate based chemical sensors
- Statistical analysis of Lamivudine on glass, gold, and silver chemical sensors
- Dolutegravir on citrate based chemical sensors
- Statistical analysis of Dolutegravir on glass, gold, and silver chemical sensors
A comparison with the spectrum of the powder sample was made to observe changes in vibration modes. Further in the spectral range, carbon and nitrogen double bonds of the adenine ring appear at 1314 cm-1, which is a red shift of 12 cm-1 from the powder band. In the next section, a statistical evaluation of the peaks marked in the table was performed.
The graphs shown in Figure 3.17 depict the changes in peak area of the adenine functional group in response to different scaffolds. In the case of the gold sensor, a significant improvement in R2 of 0.98 (p < 0.01) and calibration sensitivity of 14761 was the result due to the improved sensor signal as well as the absence of interference from the simple scaffold of glass. The top graph is of the glass substrate where the R2 value was improved to 0.90 (p<0.05) by the adenine assay, also the calibration sensitivity was also increased to 736.
From the data, R1 and R2 were chosen as functional groups of interest due to the close connection to the amine and hydroxyl groups, respectively, for all three scaffolds. In the next section, a statistical evaluation of the peaks highlighted in the table was performed using equations from section 2 .6. The difference in peak number speaks to the changes in bond length mediated by intermolecular forces between the oxygens on the glass and the hydrogens in the analyte [39-41].
Finally, double bonds of the aromatic benzene ring were detected at 1645 cm-1 like the values obtained in the other platforms.
SERS analysis of APIs on cysteamine-based chemical sensors
- Tenofovir on cysteamine-based sensors
- Statistical evaluation of Tenofovir on glass and cysteamine-based chemical sensors
- Lamivudine on cysteamine-based sensors
- Statistical evaluation of Lamivudine on glass and cysteamine-based chemical sensors
- Dolutegravir on cysteamine based chemical sensors
- Statistical analysis of Dolutegravir on glass, gold and silver chemical sensors
Graphs were used to determine R2 values and calibration sensitivity as the slope of the line. The data in the figure above show the statistical response from the 1330 cm-1 vibrational band of the primary amide of TDF. In the next part, experiments were performed with Lamivudine to compare the performance of chemical sensors against glass.
In addition, the amine group distortion appeared again, linked to the carbon double bonds of the R1. The reason can be placed on the high calibration sensitivity and the relatively low standard deviation of the silver substrate compared to gold and glass. In the latter case, the background noise of the glass signal increased the standard deviation of the sample group which decreased the analytical sensitivity.
In the next section, statistical evaluations of the 1400 cm-1 and 1520 cm-1 bands are performed similarly to the DLG experiments on citrate-based chemical sensors. The following figure shows a comparison of the 1520 cm-1 vibration mode with the corresponding parameter values. From the table above, the data are from calculations using the peak area of the methyl group at 1400 cm-1 and the primary amine at 1520 cm-1.
-Lambert's law for optical tissue diagnostics: current state of the art and main limitations.
Discussion
- Surface coating, morphology, and characterization of the chemical sensors
- SERS on Tenofovir using gold and silver chemical sensors
- SERS on Lamivudine using gold and silver chemical sensors
- SERS on Dolutegravir using gold and silver chemical sensors
An assessment of the peak area of the tremors in the 800-900 cm-1 and 1400-1500 cm-1 regions was made in Section 3.1.1 and the trends showed the most intense response of the silver sample group compared to the gold. Like citrate, the broadening results from the adsorption of the cysteamine onto the sensors in a geometry that causes redshift in both metal sample groups. However, the spectral quality of the glass sample group was poor compared to the metal substrates.
This observation is further supported by the amine stretching seen at the end of the spectrum (1600 cm-1) where cysteamine shows a red shift indicating bond stretching that may be caused by the nitrogen lone pairs and hydrogens of the amine group, for citrate. the red shift is less pronounced (tables 5 and 11). This contribution of the carbonyl is smaller, probably due to repulsive forces between the lone pairs of the corresponding atoms. In this study, the molecular vibrations of the drug were studied using gold and silver chemical sensors.
The statistical results from the experiments were examined to make connections with the molecular vibrational data of the peaks of interest discussed above. This can be explained by the size of the analyte molecule, which is too large to allow bond propagation as other APIs and in addition. Calculations of the sensor parameters investigated in this part of the study showed that the best linear fit came from Au@Cit/Au for the methyl group (1400 cm-1) and the amine group 1500 cm-.
The LOD values were lower for silver compared to the gold and this value is inversely proportional to the slope of the linear fit, which is significantly higher on Ag@Cit/Ag.
Conclusion
Future work will involve other synthesis techniques such as lithography, which enable a stable size distribution and determination of SERS enhancement factor. Second, other activities will include the use of more advanced techniques to manufacture the sensor platforms ie; Lithography to have more reproducibility and higher sensitivity to enable improvement of the sensor properties. Such work is important in the development of cost-effective, simplified methods for monitoring ARV medication as a way to assist the healthcare sector in providing quality health products that provide an optimal standard of living for citizens of the African continent. continent assured.
Supplementary information
DLG/Au@Cit/Au
DLG/Ag@Cit/Ag
DLG/Au@Cys/Au
DLG/Ag@Cys/Ag
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