<p>To evaluate the efficiency of transfection, fluorescence microscopy (Leica DMI6000 B at 20x magnification) was performed on HEK293 cells transfected with LNP-formulated DNA and mRNA of pcDNA 3.1 eYFP, Minicircle DNA as technical positive control and LNP without cargo.</p>
<p>To evaluate the efficiency of transfection, we performed fluorescence microscopy (Leica DMI6000 B at 20x magnification) on HEK293 cells transfected with LNP-formulated DNA and mRNA of pcDNA 3.1 eYFP, Minicircle DNA as technical positive control and LNP without cargo.</p>
<p>24 h, 48 h and 72 h post-transfection, we observed in the conditions with Lipofectamine alone, or combined with DNA or RNA, no fluorescence, indicating unsuccessful transfection. Similarly, no fluorescence was seen in cells treated with LNPs alone or in combination with DNA or RNA. When LNPs were combined with Minicircle DNA, clear fluorescence was observed, indicating successful transfection and expression of our eYFP reporter under this condition (figure X). However, a strong background fluorescence from the OptiMEM medium was observed, complicating the analysis.</p>
<p>Overall, among all the tested conditions, the LNP formulation with Minicircle DNA was the only combination that resulted in noticeable fluorescence, suggesting it to be the most effective transfection method for HEK293 cells in this experiment.</p>
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<H5text="SEM"/>
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<p>Scanning Electron Microscopy (SEM) (Phenom ProX, Thermo Fisher) was employed to examine the morphology and surface characteristics of Cayman LNPs. The SEM images revealed that the LNPs displayed a generally spherical morphology with a relatively smooth surface (Figure X). The average particle size was approximately 200 nm. However, a heterogeneous distribution of particle sizes was observed, with some larger, round structures present. These larger structures could potentially indicate aggregated LNPs.</p>
<p>Scanning Electron Microscopy (SEM) (Phenom ProX, Thermo Fisher) was employed by us to examine the morphology and surface characteristics of Cayman LNPs. The SEM images revealed that the LNPs displayed a generally spherical morphology with a relatively smooth surface (Figure X). The average particle size was approximately 200 nm. However, a heterogeneous distribution of particle sizes was observed, with some larger, round structures present. These larger structures could potentially indicate aggregated LNPs.</p>
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<p>While many particles retained their structural integrity, the presence of these aggregates suggests that, under certain conditions, the LNPs may tend to cluster. It is important to note that for SEM analysis, the samples were dried and observed under vacuum, which probably have affected the structure and shape of the LNPs. This preparation process can introduce artifacts that would not typically be present in solution and should be considered when interpreting the results. Additionally, the contrast under vacuum conditions was too low to reliably distinguish the LNPs with sufficient detail. It provided a useful initial glimpse into the world of nanoparticles. Further complementary techniques will be needed for a more accurate and detailed characterization.</p>
<H4text="Corden LNP"/>
<H5text="Transfection"/>
<p>Fluorescence microscopy with the Leica DMI6000 B microscope at 20x magnification was conducted on HEK293 cells transfected with LNPs containing pcDNA 3.1 eYFP DNA and mRNA. Minicircle DNA served as the positive control, while LNPs without cargo acted as the negative control. Cells were imaged at 24 h, 48 h, and 72 h post-transfection.</p>
<p>Fluorescence microscopy with the Leica DMI6000 B microscope at 20x magnification was by us on HEK293 cells transfected with LNPs containing pcDNA 3.1 eYFP DNA and mRNA. Minicircle DNA served as the positive control, while LNPs without cargo acted as the negative control. Cells were imaged at 24 h, 48 h, and 72 h post-transfection.</p>
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<H5text="Cryo-EM"/>
<p>Cryo-EM (cryogenic electron microscopy) as a form of transmission electron microscopy (TEM) was performed using a JEOL JEM-2200FS electron microscope (JEOL, Freising, Germany) operating at 200kV, equipped with a cold field emission electron gun. The sample preparation and imaging were carried out at cryogenic temperatures, which allowed for the visualization of LNPs in their native hydrated state.</p>
<p>Cryo-EM (cryogenic electron microscopy) as a form of transmission electron microscopy (TEM) was performed by us using a JEOL JEM-2200FS electron microscope (JEOL, Freising, Germany) operating at 200kV, equipped with a cold field emission electron gun. The sample preparation and imaging were carried out at cryogenic temperatures, which allowed for the visualization of LNPs in their native hydrated state.</p>
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<p>FACS analysis was performed 72 h post-transfection to evaluate the transfection efficiency of the SORT LNP in HEK293. The relative percentage of fluorescent cells was determined by measuring the percentage of FITC-A+ cells, followed by normalization to the negative control and fold change calculation.</p>
<p>We performed FACS analysis 72 h post-transfection to evaluate the transfection efficiency of the SORT LNP in HEK293. The relative percentage of fluorescent cells was determined by measuring the percentage of FITC-A+ cells, followed by normalization to the negative control and fold change calculation.</p>
<p>The SORT LNP-transfected sample carrying Minicircle DNA exhibited a significant increase in fluorescence compared to the lipofectamine transfection of Minicircle DNA, with approximately 14 times more fluorescent cells compared to the lipofectamine-transfected sample (Figure a). This substantial difference indicates that the transfection efficiency with LNPs is markedly higher than with lipofectamine, demonstrating the superior performance of our LNP formulation in delivering nucleic acids to HEK cells.</p>
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<p>Both the particle size distribution and the Zeta potential were measured using the Nanotrack Wave II. We could assume that the particles exhibit a polarized Zeta potential, which is sufficient to provide electrostatic stabilization, thereby preventing aggregation and maintaining particle stability. For effective targeting of lung cells which have negatively charged surfaces, a negative polarity is desirable meaning the LNP is positively charged, so there can be electrostatic attraction to lung epithelial cells. We were able to show that our SORT LNP has these properties regardless of the load. Furthermore we could <ahref="https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Physical_Methods_in_Chemistry_and_Nano_Science_(Barron)/02%3A_Physical_and_Thermal_Analysis/2.05%3A_Zeta_Potential_Analysis"title="StabZeta">determine the stability via the Zeta potential</a>. In detail the mean of the Zeta potential lays at 16.2 mV for the SORT LNP with Minicircle DNA as cargo, indicating incipient stability, at 59.45 mV for the SORT LNP with pcDNA 3.1 eYFP as cargo, indicating good stability and at 88.22 mV for the SORT LNP without cargo indicating excellent stability (Figure z). The good stability of the SORT LNP with pcDNA 3.1 eYFP is crucial for our purposes, as it ensures effective delivery and performance. In contrast, the stability of the LNPs with Minicircle DNA can be considered secondary, as it primarily serves as a positive transfection control and is not central to our main objectives.</p>
<p>We measured both the particle size distribution and the Zeta potential using the Nanotrack Wave II. We could assume that the particles exhibit a polarized Zeta potential, which is sufficient to provide electrostatic stabilization, thereby preventing aggregation and maintaining particle stability. For effective targeting of lung cells which have negatively charged surfaces, a negative polarity is desirable meaning the LNP is positively charged, so there can be electrostatic attraction to lung epithelial cells. We were able to show that our SORT LNP has these properties regardless of the load. Furthermore we could <ahref="https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Physical_Methods_in_Chemistry_and_Nano_Science_(Barron)/02%3A_Physical_and_Thermal_Analysis/2.05%3A_Zeta_Potential_Analysis"title="StabZeta">determine the stability via the Zeta potential</a>. In detail the mean of the Zeta potential lays at 16.2 mV for the SORT LNP with Minicircle DNA as cargo, indicating incipient stability, at 59.45 mV for the SORT LNP with pcDNA 3.1 eYFP as cargo, indicating good stability and at 88.22 mV for the SORT LNP without cargo indicating excellent stability (Figure z). The good stability of the SORT LNP with pcDNA 3.1 eYFP is crucial for our purposes, as it ensures effective delivery and performance. In contrast, the stability of the LNPs with Minicircle DNA can be considered secondary, as it primarily serves as a positive transfection control and is not central to our main objectives.</p>
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<p>The size distribution for all three samples shows a predominantly monomodal, yet broad, distribution with diameters ranging between 50 nm and 700 nm, with the peak of the distribution lying between 150 nm and 200 nm (Figure d). SORT LNPs without DNA exhibited larger radii, with a peak around 300 nm. The SORT LNP containing Minicircle DNA suggests the presence of larger aggregates with diameters exceeding 1 µm. The likely reason for this variable particle size distribution, despite loading with different types of DNA, could be attributed to the manufacturing method. Since the LNPs were not produced using an extruder but rather via dialysis, this is highly plausible.</p>
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<H5text="Dynamic Light Scattering (DLS)"/>
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<p>Text :D</p>
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<p>Cryo-EM analysis was also performed of SORT LNPs with the same JEOL JEM-2200FS microscope at 200kV, allowing visualization of LNPs in their native hydrated state. The images show spherical LNP structures around 100 nm, with some larger aggregates also present (data not shown). These aggregates likely result from interactions between particles due to the non-extrusion-based preparation method, which may explain the variability in particle size. Additionally, particles potentially representing different LNP populations or overlapped structures with low contrast were observed (Figure X). The low sample concentration likely contributed to the limited number of visible particles.</p>
<p>Cryo-EM analysis was also performed of SORT LNPs by us with the same JEOL JEM-2200FS microscope at 200kV, allowing visualization of LNPs in their native hydrated state. The images show spherical LNP structures around 100 nm, with some larger aggregates also present (data not shown). These aggregates likely result from interactions between particles due to the non-extrusion-based preparation method, which may explain the variability in particle size. Additionally, particles potentially representing different LNP populations or overlapped structures with low contrast were observed (Figure X). The low sample concentration likely contributed to the limited number of visible particles.</p>
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<p>Overall, while the Cryo-EM data confirm the presence and general morphology of LNPs, variability in size and the presence of aggregates highlight potential areas for optimization, such as refining sample concentration and preparation methods to achieve more consistent particle formation.</p>
<p>Overall, while the Cryo-EM data confirm the presence and general morphology of LNPs that also fall within the diameter range specified by Wang et al. for SORT LNPs at smaller than 200 nm [link]. The variability in size and the presence of aggregates highlight potential areas for optimization, such as refining sample concentration and preparation methods to achieve more consistent particle formation.</p>
<H5text="DLS"/>
<p>We used Dynamic Light Scattering (DLS) to assess the size distribution of our SORT LNPs by measuring the fluctuations in scattered light due to particle motion. The hydrodynamic diameter was calculated using the Stokes-Einstein equation, considering the diffusion coefficient, temperature, and viscosity of the medium.</p>
Results for hydrodynamic radius determination by DLS Measurements for our SORT LNP, indicating a radius of approximately 100 nm.
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<p>The results showed a hydrodynamic diameter of SORT LNPs yielding an average radius of approximately 100 nm (Figure X). These findings are consistent with our previous applied size determination methods, such as Zeta potential and Cryo-EM, which also indicated similar particle dimensions in appropriate range for our research and medical applications.</p>
