DMON-PS1-4 were then prepared by mixing the corresponding triethoxysilylated photosensitizers (
Figures 1A, 2A, 3A and 4A) in the presence of tetraethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, following a one-pot known procedure using NaSal (sodium salicylate) and cationic surfactant CTAB as structure directing agents and triethanolamine as a catalyst. [
29] The dendritic structure and the presence of radial mesopores were clearly shown with transmission electron microscopy (TEM) (
Figures 1B, 2B, 3B and 4B) of DMONPS1-4. DLS showed well-dispersed nanoparticles from 95-100 nm, hydrodynamic diameters in agreement with TEM images. The photosensitizers were clearly incorporated inside the structure of DMONPS1-4 as shown by UV-Vis spectra. (
Figures 1C, 2C, 3C and 4C). With PS1 possessing four triethoxysilyl groups, the Q bands were visible after incorporation in DMONPS1 despite light scattering, which was not the case for DMONPS2, DMONPS3 due to a lower amount of incorporation. The Q1 band was present for the chlorin e6 derivative (DMONPS4) showing that the structure was not damaged during the mild sol-gel method used for the preparation of the nanoparticles. N
2 adsorption-desorption was studied for all the DMONPS. (
Figures 1D, 2D, 3D and 4D, Table 1). All the nanoparticles showed type IV isotherms. The Brunauer−Emmett−Teller (BET) surface area and the total pore volume of DMONPS1 were 110 m
2.g
−1 and 0.44 cm
3.g
−1 respectively. The capillary condensation step occurred in the relative pressure (P/P0) of 0.8−0.9, corresponding to a large pore size of ∼24.4 nm (inset of
Figure 1D). Interestingly, with DMONPS2 and DMONPS3, the BET-specific surface area increased to 356, 353 m
2.g
−1, with an increase of the pore volumes to 1.78, 1.65 cm
3.g
−1 and a decrease of the pore size to 19.5 and 18.2 nm respectively. The structure of DMONPS4 was between DMONPS1 and DMONPS2-3 with a BET-specific surface area of 266 m
2.g
−1 a pore volume of 1.52 cm
3.g
−1 and a pore size of 22.6 nm. In order to complex siRNA, functionalization of DMONPS1-4 with lysine (
Scheme 1), by amination with aminopropyltriethoxysilane (APTES), coupling with protected lysine, and deprotection was then performed. DMONPS1-4 showed a negative zeta potential in agreement with the deprotonation of Si-OH in water. After amination, the zeta potential turned positive (
Table 1) and after functionalization with lysine, high zeta potential values were observed indicating that the functionalization was successful, except for DMONNPS4-Lys.
Figure 1.
A) The tetraaminophenylporphyrin with four triethoxysilyl groups used for the preparation of DMONPS1. B) DMONPS1 as shown by TEM, the dendritic structure is visible. C) UV-Vis spectra in EtOH of the silylated photosensitizer(PS1) and the corresponding DMONPS1, the photosensitizer is encapsulated inside the framework of DMONPS1, the Soret and four Q bands are visible. D) Nitrogen adsorption–desorption at 77 K (BET). Insert BJH adsorption (dV/dw) Pore Volume.
Figure 1.
A) The tetraaminophenylporphyrin with four triethoxysilyl groups used for the preparation of DMONPS1. B) DMONPS1 as shown by TEM, the dendritic structure is visible. C) UV-Vis spectra in EtOH of the silylated photosensitizer(PS1) and the corresponding DMONPS1, the photosensitizer is encapsulated inside the framework of DMONPS1, the Soret and four Q bands are visible. D) Nitrogen adsorption–desorption at 77 K (BET). Insert BJH adsorption (dV/dw) Pore Volume.
Figure 2.
A) The monosilylated aminophenylporphyrin used for the preparation of DMONPS2. B) DMONPS2 as shown by TEM, the dendritic structure is visible, the nanoparticles seem aggregated. C) UV-Vis spectra in EtOH of the silylated photosensitizer(PS2) and the corresponding DMONPS2, the photosensitizer is encapsulated inside the framework of DMONPS2, the Soret band is visible. D) Nitrogen adsorption–desorption at 77 K (BET). Insert BJH adsorption (dV/dw) Pore Volume.
Figure 2.
A) The monosilylated aminophenylporphyrin used for the preparation of DMONPS2. B) DMONPS2 as shown by TEM, the dendritic structure is visible, the nanoparticles seem aggregated. C) UV-Vis spectra in EtOH of the silylated photosensitizer(PS2) and the corresponding DMONPS2, the photosensitizer is encapsulated inside the framework of DMONPS2, the Soret band is visible. D) Nitrogen adsorption–desorption at 77 K (BET). Insert BJH adsorption (dV/dw) Pore Volume.
Figure 3.
A) The monosilylated aminoporphyrin used for the preparation of DMONPS3. B) DMONP3 as shown by TEM, the dendritic structure is visible. C) UV-Vis spectra in EtOH of the silylated photosensitizer(PS3) and the corresponding DMONPS3, the photosensitizer is encapsulated inside the framework of DMONPS3, the Soret band is visible. D) Nitrogen adsorption–desorption at 77 K (BET). Insert BJH adsorption (dV/dw) Pore Volume.
Figure 3.
A) The monosilylated aminoporphyrin used for the preparation of DMONPS3. B) DMONP3 as shown by TEM, the dendritic structure is visible. C) UV-Vis spectra in EtOH of the silylated photosensitizer(PS3) and the corresponding DMONPS3, the photosensitizer is encapsulated inside the framework of DMONPS3, the Soret band is visible. D) Nitrogen adsorption–desorption at 77 K (BET). Insert BJH adsorption (dV/dw) Pore Volume.
Table 1.
Data for DMON.
DMONPS |
DLS (nm) |
ZETA Potential (mV) |
BET (m2.g-1) |
Pore size (nm) |
Pore volume cm3.g-1
|
DMONPS1 |
100 |
-8.1 |
110 |
24.4 |
0.44 |
DMONPS2 |
92 |
-8.5 |
356 |
19.5 |
1.78 |
DMONPS3 |
96 |
-10.4 |
353 |
18.2 |
1.65 |
DMONPS4 |
95 |
-7.5 |
265 |
22.6 |
1.52 |
DMONPS1-NH2 |
100 |
6.0 |
/ |
/ |
/ |
DMONPS2-NH2 |
99 |
4.8 |
/ |
/ |
/ |
DMONPS3-NH2 |
100 |
5.1 |
/ |
/ |
/ |
DMONPS4-NH2 |
100 |
6.3 |
/ |
/ |
/ |
DMONPS1-Lys |
99 |
42.0 |
/ |
/ |
/ |
DMONPS2-lys |
99 |
26.3 |
/ |
/ |
/ |
DMONPS3-Lys |
100 |
26.4 |
/ |
/ |
/ |
DMONPS4-Lys |
100 |
6.0 |
/ |
/ |
/ |
Figure 4.
A) The trisilylated chlorin e6 used for the preparation of DMONPS4. B) DMONP4 as shown by TEM, the dendritic structure is visible. C) UV-Vis spectra in EtOH of the silylated photosensitizer(PS4) and the corresponding DMONPS4, the photosensitizer is encapsulated inside the framework of DMONPS4, the Soret and Q1 bands are visible. D) Nitrogen adsorption–desorption at 77 K (BET). Insert BJH adsorption (dV/dw) Pore Volume.
Figure 4.
A) The trisilylated chlorin e6 used for the preparation of DMONPS4. B) DMONP4 as shown by TEM, the dendritic structure is visible. C) UV-Vis spectra in EtOH of the silylated photosensitizer(PS4) and the corresponding DMONPS4, the photosensitizer is encapsulated inside the framework of DMONPS4, the Soret and Q1 bands are visible. D) Nitrogen adsorption–desorption at 77 K (BET). Insert BJH adsorption (dV/dw) Pore Volume.
Scheme 1.
Functionalization of DMONPS1-4 with lysine amino acid (DMONPS1-4-Lys) in order to complex siRNA.
Scheme 1.
Functionalization of DMONPS1-4 with lysine amino acid (DMONPS1-4-Lys) in order to complex siRNA.
The nanoparticles were then incubated with cancer cells for 24 h, at a concentration of 50 µg.mL
-1, which was adequate for imaging, and confocal microscopy was performed (
Figure 5). The nanoparticles were excited at 420 nm, in the Soret band of the porphyrin and chlorin.
Figure 5.
Confocal microscopy imaging of MCF-7 cancer cells incubated with DMONPS1-4, DMONPS1-4-NH2 or DMONPS1-4-Lys, for 24h. ℷexcitation = 420 nm ℷemission = 630-670 nm. Membranes were stained with a cell mask 15 Min. before observation. ℷexcitation = 561 nm ℷemission = 565-629 nm.
Figure 5.
Confocal microscopy imaging of MCF-7 cancer cells incubated with DMONPS1-4, DMONPS1-4-NH2 or DMONPS1-4-Lys, for 24h. ℷexcitation = 420 nm ℷemission = 630-670 nm. Membranes were stained with a cell mask 15 Min. before observation. ℷexcitation = 561 nm ℷemission = 565-629 nm.
Cytotoxicity studies were then performed (
Figure 6). 25 µg.mL
-1 was the adequate concentration to carry out photodynamic therapy (PDT) experiments as the nanoparticles presented low toxicity above 75% after three days. The cells were classically irradiated [
26] at 405 nm in the Soret band, for 5 min. or at 650 nm for 20 min. in the QI band, but PDT effects were not observed (data not shown). Indeed we believe that the tetrasulfide group quenches the formation of singlet oxygen through oxidation. [
30] The photosensitizers allow only imaging of cancer cells.
Figure 6.
Cytotoxicity studies of MCF-7 cancer cells were performed through incubation with DMONPS1-4, DMONPS1-4-NH2 or DMONPS1-4-Lys, for 72h. The cytotoxicity was monitored with the MTT assay.
Figure 6.
Cytotoxicity studies of MCF-7 cancer cells were performed through incubation with DMONPS1-4, DMONPS1-4-NH2 or DMONPS1-4-Lys, for 72h. The cytotoxicity was monitored with the MTT assay.
Complexation of DMONPS1-4-Lys with siRNA (Inhibitor Apoptotic Protein) IAP was then performed (
Figure 7) and monitored with a gel retardation assay. Proapoptotic siRNA would inhibit the production of anti-apoptotic proteins, with the activation of the apoptotic pathway, leading to cell death. A very good complexation was noticed at concentrations of 1/25 for DMONPS1-2-lys, and 1/10 for DMONPS3-4-lys.
Figure 7.
Agarose gel-retardation assay with DMONPS1-4-Lys, complexed with siRNA (negative control (A)), at different weight ratios ranging from 1/10 to 1/50. Electrophoresis was immediately performed after complex formation for 30 min at 37 °C.
Figure 7.
Agarose gel-retardation assay with DMONPS1-4-Lys, complexed with siRNA (negative control (A)), at different weight ratios ranging from 1/10 to 1/50. Electrophoresis was immediately performed after complex formation for 30 min at 37 °C.
None of the nanoparticles were able to deliver the siRNA except DMONPS3-Lys. DMONPS3-Lys led to 90% MCF-7 survival whereas DMONPS3-Lys-siRNA led to 31% of cancer cell death. This result could be explained by the structure of the nanoparticles. BET analysis showed that DMONPS3 possess a high specific surface area with pore size suitable for siRNA encapsulation, furthermore, they were not aggregated with a hydrodynamic diameter suitable for the delivery of siRNA in the cytoplasm of the cells. We suggest that the high level of GSH in the cytoplasm of cancer cells allowed delivery of siRNA through cleavage of the tetrasulfide link present in the structure of the DMONPS3-Lys-siRNA complex.
After that, we tested the encapsulation of the FVIII protein factor as a model protein, in DMONPS1-Lys and DMONPS3-Lys. FVIII factor is a protein that plays a crucial role in blood clotting. [
31] It is produced in the liver and circulates in the blood. FVIII deficiency is the cause of hemophilia A, a genetic bleeding disorder Hemophilia A patients require regular infusions of FVIII to prevent bleeding episodes. FVIII is administered intravenously. The half-life of FVIII in the body is approximately 8-12 hours. Therefore, encapsulation of FVIII could be of high interest. Furthermore, the global charge of factor VIII is negative. This is because FVIII is a glycoprotein, [
32] and the carbohydrate component contains negatively charged molecules, such as sialic acid and sulfate groups, which contribute to the overall negative charge of the protein.
Table 2.
Data for the encapsulation of FVIII factor in DMONPS1-Lys and DMONPS3-Lys.
Table 2.
Data for the encapsulation of FVIII factor in DMONPS1-Lys and DMONPS3-Lys.
DMONPS |
DLC 2 mg/mL FVIII |
DLE 2 mg/mL FVIII |
DLC 4 mg/mL FVIII |
DLE 4 mg/mL FVIII |
DMONPS1-Lys |
14 % |
40 % |
/ |
/ |
DMONPS3-Lys |
12% |
35% |
25% |
42% |
We tested the encapsulation of FVIII in DMONPS1,3-Lys. DLC and DLE at 2 mg/mL of protein in PBS were quite interesting with 12-14% of loading and 35-40% of DLE. By increasing the amount of protein in the feeding solution, higher DLC was reached with DMONPS3-Lys up to 25% of DLC.