Elemental analysis and some physical measurements of La(III) nanocomplexes (
In this study, a convenient synthesis of a series of La(III) complexes (in nanoscales) with different organic ligands was prepared by green chemical method. The physicochemical properties of the nanocomplexes were obtained. The SEM and TEM techniques were used to confirm the nanosize and morphology. The cytotoxicity of the newly synthesized compounds was demonstrated and tested for their anticancer activity against common pathogenic organisms and against human epithelial colorectal adenocarcinoma cells (Caco2), Vero, and MCF-7 cells. By examining its pharmacological activity, we were able to identify new potent and selective anticancer agents. Also, the structures succeeded to affect and stop the growth of Klebsiella pneumonia strain, and the results revealed promising activity. In addition, an electrospinning technique was used for the fabrication of novel bio-medicated nanofibers which are applied for wound dressing as local chemotherapy for skin injuries.
- anticancer activity
- MCF-7 cells
- flow cytometry
- wound dressing
The Environmental Protection Agency defined the green chemistry or sustainable chemistry as “the production of chemical products and processes which have the ability to reduce or eliminate the use or generation of hazardous substances.” In recent years there is an expectation that chemists and chemical engineers should design greener and more sustainable chemical processes, and it was expected that this trend will continue to grow over the next few decades .
Studies on metal-based drugs offer promise in the fight against cancer, which is the main aim of the inorganic chemistry [2, 3].
The metal-based anticancer drugs are driven by the necessity to fill the gap in tumor chemotherapy in order to minimize the undesirable side effects and enlarge the spectrum of activity for more tumor types and metastatic cancers. The Schiff base structures play a key role in studying the mechanism of the transformation and racemization reaction in biological systems due to the similarity of their structures to the natural biological system [4, 5, 6, 7, 8, 9, 10, 11].
Among various metal complexes, La(III) complexes have been intensively investigated due to their more physiological activities and lower toxicities after coordination with ligand, so, in recent years people have paid great interest to synthesis, DNA interaction, and anticancer activity of La(III) complexes [12, 13, 14, 15, 16].
Dressings play multimodal roles in wound healing process, such as preventing infections, absorbing exudates, and maintaining moisture, and thus are indispensable . Electrospinning is the method to fabricate ultrafine fibers from polymer solution(s) or melt(s) with diameters ranging from nanometers to micrometers .
The obtained results revealed the successful implementation of the nanoparticle-nanofiber as a local wound dressing especially for skin injuries.
2.1. Materials and reagents
In this study all chemicals used were of highest purity. Organic solvents such as ethyl alcohol and dimethylformamide (DMF) were spectroscopically pure from the British Drug House (BDH). The other materials were purchased from Sinopharm Chemical Reagent Co., Ltd. and used without further purification. In addition to the 5-bromosalicylaldehyde (Sigma-Aldrich), La(NO3)3·6H2O (Merck) were also used.
In open capillaries melting points (°C, uncorrected) were determined on a Gallenkamp melting point apparatus (Sanyo Gallenkamp, Southborough, UK). In the Microanalytical Center, Cairo University (C, H, N, and S) were carried out. 1H NMR spectra (DMSO-
2.3. Cytotoxicity assay
Different concentrations of the nanometal complexes were tested for their cytotoxicity against Vero, Caco2, and MCF-7 cell lines using (MTT) Thiazolyl Blue Tetrazolium Bromide method according to [19, 20]. In brief, Vero, Caco2, and MCF-7 cells (10 × 103) were cultured in a 96-well plate overnight at 37°C, 5% CO2, and 88% humidity. The total volume of used DEMEM supplemented medium and the synthesized compound supernatant was 200 μL with final concentrations of 10, 20, 30, 40, 60, 80, and 100 mg/L. The plate was incubated at 37°C and 5% CO2 for 3 days. After incubation, debris and dead cells were removed by washing three times with fresh medium. Twenty microliters of MTT solution (5 mg/mL of MTT in PBS buffer) was added to each well and shook for 5 min at 150 rpm to thoroughly mix the MTT into the media. The cells were incubated at 37°C and 5% CO2 for 3–5 h to metabolize MTT by viable cells. Two hundred microliter dimethyl sulfoxide (DMSO) was added to each well and shook again for 5 min at 150 rpm, and then the viability of the cells was calculated by measuring the optical density at 630 nm subtracted from optical density at 570 nm . The percentage of viability cells was calculated by comparison with control cells (without adding the synthesized compounds to the cells) using the equation (A) test/(A) control × 100.
2.4. Flow cytometry
To discriminate living cells from dead cells or for cell cycle analysis, propidium iodide (PI) can be used according to Léonce et al. . This analysis is based on the stoichiometric binding of PI to intracellular DNA. At the end, cells were washed with PBS and collected by trypsinization. Cells were then resuspended in warm PBS and fixed with 4 ml ice-cold ethanol. Finally, in darkness, cells were stained with 0.5 ml of warm PI solution; 7 ml of PI solution consists of 0.35 ml of PI stock solution (1 mg/ml), 0.7 ml RNase A stock solution (1 mg/ml), and 6 ml of PBS and incubated in darkness for 30 minutes. The samples were kept on ice until flow cytometric analysis.
2.5. Preparation of (chitosan-La(III) nanocomplex) composite nanofibers
Chitosan (CS) was dissolved in 50% acetic acids at room temperature under moderate stirring for 12 h to form a homogeneous solution, and then the solution of La complex nanoparticles was quietly adding. The total solution was fixed to 3 wt.%. The solution was filled in a 20 ml NORM-JECT Luer Lock tip plastic syringe having an 18-gauge stainless steel needle with 90° blunt end. The electrospinning setup included a high voltage power supply, purchased from the NanoNC, Inc. (S. Korea), and a nanofiber collector of aluminum foil that covered a laboratory-produced roller with the diameter of 10 cm. The collector was placed at 10 cm tip-to-collector distance (TCD) .
2.6.1. Synthesis of complex nanoparticles by sonochemistry method (green chemistry)
Ten milliliter of 0.1 M solution of La(NO3)3.6H2O in ethanol was positioned in a high-density ultrasonic probe, operating at 24 kHz with a maximum power  output of 400 W. Ten milliliter of 0.1 M solution of N'-((E)-5-bromo-2-hydroxybenzylidene)-6-(((E)-5-bromo-2-hydroxybenzylidene)amino)-4-oxo-2-thioxo-1,2,3,4-tetrahydrothieno[3,2-d]pyrimidine-7-carbohydrazide H2L1, N-(2-mercaptophenyl) benzamide H2L2, and 2-((2-mercapto- phenyl) imino)-1,2-diphenylethan-1-ol H2L3 was added dropwise. The obtained precipitates were allowed to evaporate at room temperature to obtain the complex nanoparticle in powder form.
3. Results and discussion
3.1. Elemental analyses for nanometal complexes
In the present investigation, the analytical data of the prepared metal complexes suggest the structures as given in Figure 6. The physicochemical results of the newly synthesized compounds were presented in Table 1. The obtained results were in good agreement with those calculated for the suggested formulae. The melting points were sharp, indicating the purity of the prepared nanometal complexes. The proposed formula of the nanometal complexes is according to the following general equations:
|Compd. code||(Empirical formula)||M.P. (°C)||Color (yield %)||(%) found (calcd.)|
|<350||Faint orange (80.54)||29.90 (30.01)||1.32 (1.56)||9.92 (10.00)||7.58 (7.62)||20.51|
|110||Dark gray (85.49)||2.94 (3.06)||27.75 (27.87)||5.40 (5.71)||9.80 (10.00)||57.88|
|165||Page (79.80)||2.83 (2.90)||36.54 (36.31)||4.55 (4.83)||8.33 (8.47)||3.39|
3.2. 1H NMR spectra
The 1HNMR spectra (Figure 1, Table 2) of the La (III) nanocomplex
In addition to the 1H NMR spectra of complex
3.3. IR spectra and mode of bonding
In order to ascertain the mode of bonding, the IR spectrum of the free ligands was compared with those of their La complexes. By careful comparison of the spectra of the complexes with those of the free ligands, it was found that the band at 3430 cm−1 is found to be disappeared by complexation suggesting the involvement of OH groups of the phenolic groups in complex formation with their deprotonation. The bands due to NH and SH are shifted to higher or lower frequencies indicating the participation of –N and –S donors in the coordination, while the bands due to C=O are unchanged. The strong bands at 1622 and 1298 cm−1 due to υC=N and υC▬O (azomethine and phenolic groups) are shifted to lower wave number 1609–1565 and 1280–1242 cm−1, respectively, in metal complexes indicating the participation of nitrogen of azomethine and oxygen of phenolic group in complexation. The complexes showing also three bands at the range 1480–1400, 1380–1350, and 1170–1020 cm−1 indicate the unidentate coordination mode of the nitrate group. The curves also, showed that shift in the peaks of O▬H, C▬O, C▬S groups (complex
3.4. Molar conductivity measurements
The conductivity Λm value of the La nanocomplexes
3.5. Electronic spectral data
The assignments of the significant electronic spectral absorption band of the nanometal complexes are given in Table 3. Two absorption peaks were observed in the spectra range of 210–227 and 279–337 nm due to п-п* and n-п* transitions, respectively, due to benzene and the azomethine (CH=N) function [26, 29]. Moreover, the spectra of complexes indicate no significant absorption in the visible region due to the absence of
|Compd. no.||μeff (B.M.)||Absorption bands (nm)|
3.6. Magnetic susceptibility
The following equation was used to calculate the magnetic susceptibility of the La nanocomplexes:
where C, calibration constant of standard; l, length of sample in filled tube; R0, reading of empty sample tube; R, reading with sample; χg gram magnetic susceptibility.
The gram magnetic susceptibility of the complexes was found in the range −2.2098 × 10−6 –(-2.3013 × 10−6) cm3 mol−1, respectively. Negative values of χg show that these complexes are diamagnetic in nature or there is no significant magnetic moment (Table 3).
3.7. Thermal analysis
Thermogravimetric analyses (TGA) of the La nanocomplexes were used to determine the thermal stability of the complexes, decide whether the water molecules are lattice or coordinated, and finally suggest a scheme for thermal decomposition of these chelates. In the present investigation, heating rates were suitably controlled at 10oC min−1 under nitrogen atmosphere, and the weight loss was measured from the ambient temperature up to ∼ 600oC. The weight loss for each chelate was calculated within the corresponding temperature ranges.
Also, TGA curve of the La(III) complex of nanoscale
3.8. Powder X-ray diffraction studies
The diffraction of X-rays from the planes of a crystal (diffraction analysis) is considered as one of the important methods of the analytical work. By using X-ray diffraction which depends on the crystal properties of solids, we can identify the crystal structure of various solid compounds and identify the actual compounds from its structure, and we can also determine the arrangement of molecules in crystal . X-ray diffractometry is an important technique as it is a nondestructive, non-contrast, fast, and sensitive one. Obtained XRD data of H2L1 ligand and its La(III) complex
where β the breadth of the observed diffraction line at its half intensity maximum; K, the shape factor, 0.89; λ, the wavelength of the X-ray source used in XRD; θ, the corresponding incidence angle.
The average particle size of the nanoparticles is 15 nm. The sharp diffraction peaks of the samples indicate that the well-crystallized lanthanum complex nanocrystals can be prepared by our procedure .
3.9. EDX spectra
The amount of elements present in the percentage level of the metal complexes was identified by EDX data . EDX spectra are used to calculate the percentage level of the elements present in the metal complexes like C, O, N, S, and La that are present in the La(IIl) nanocomplex
3.10. SEM analysis
SEM technique was used to study the morphology and size of nanoparticles (Figure 4). It seems that the particles are semispherical with some agglomerations of the particles. The SEM images further revealed the stabilization of La(III)
3.11. TEM analysis
Transmission electron microscopy (TEM) can be used to directly image nanoparticles at scales approaching a single atom. TEM analysis is performed to examine the size and shape of the nanoparticles. The La(III) complex
Correlation of all results obtained for the complexes under study gives us information regarding the suggested structure of the complexes to be as in Figure 6. The fully optimized geometries of the ligand and its metal complexes were shown in Figure 7.
4.1. Cytotoxicity and anticancer activity
The cytotoxicity of the prepared nanocomplexes has been demonstrated and tested for their anticancer activity against Caco2, Vero, and MCF-7 cell lines. The obtained results revealed that complex
On the other hand, the other tested compounds have shown moderate activities against all cells; the anticancer activity is less than that recorded for
4.2. Flow cytometry
Flow cytometric analyses of propidium iodide-stained nuclei cells were performed to investigate whether treatment could induce cell cycle perturbations in human epithelial colorectal adenocarcinoma. Cell cycle parameters were compared for Caco2 cells that had been incubated for 24 h with 1 ml of IC50 concentrations of sample
Also, an additional peak was observed, consistent with aneuploid cells which contain more than 4n DNA. This peak may represent a population of cells that has escaped mitotic arrest and continued to replicate as multinuclear cells without dividing (i.e., endoreduplication), or it may be due to a small fraction of tetraploid cells which are already present in the culture, which undergo G2/M arrest, resulting in cells with 8n DNA.
4.3. Chitosan-nanocomplex 2 composite nanofibers
The chitosan played an important role in the synthesis of the composite nanofiber. The amino group has been used to stabilize metal nanoparticles , so we suggested that the free NH2 ligands of chitosan might bind to the nanoparticles and stabilized them.
The formation of the CS-stabilized NPs was further investigated by FTIR spectroscopy. The FTIR spectra of the CS-NP nanofiber and CS nanofiber attributed a broad band at the range of 3350–3510 cm−1 corresponding to the amine and hydroxyl groups. For the nanocomposite, there is a change in the shape and frequencies of the bands in this region, indicating participation of the NH2 group in the reaction. Although there is some difference in the two figures, both of them showed the basic characteristic peaks for CS at 3422 cm−1 (O▬H stretch) and 2960–2970 cm−1 (C▬H stretch), which indicated that the CS can adsorb on the formed nanoparticles in the preparation process [34, 35].
Thermogravimetric analysis (TGA) is widely used to investigate the thermal decomposition of a polymer. The TGA thermograms of pristine CS nanofiber, CS-NP composite nanofiber, at a heating rate of 20°C/min under nitrogen atmosphere are investigated. Chitosan’s nanofiber weight change between 28.27 and 100°C is associated with the loss of adsorbed and bound water. Chitosan polymer degradation started at 100°C and continued up to 333.80°C, with a 75.5% polymer weight loss [36, 37].
The CS-NP composite nanofiber exhibited a three-step degradation pattern. The first step occurred between 24.68°C and 100.86°C, which is due to water evaporation. The second and the major mass loss were observed between 100°C and 261.34°C, with a 40.42% polymer weight loss. The third step occurred between 261.34 and 367.43°C, with a 19.95% polymer weight loss with total loss of 71.27% at 367.43°C.
The NP complex was encapsulated by CS, and their sizes were in the range of 15–50 nm as shown in the TEM image of the CS–NP composite nanofiber (Figure 10). It could be observed that a considerable amount of non-spherical particle was observed. These non-spherical particles seemed to be fabricated by coalescence of two spherical particles during the nucleation process .
The morphology of electrospun (chitosan–nanoparticle) composite nanofiber is shown in Figure 11. It is clear from these figures that no phase separation has been observed and the homogeneity of the obtained nanofibers can be easily observed and the composite of the nanoparticles has been proven. It is also clear that the diameter of chitosan-nanoparticle composite nanofiber is smaller than chitosan nanofiber.
4.3.5. Antimicrobial activity
The ability of prepared La nanoparticle-coated nanofibers to cease the growth of microbes known for its human pathogenicity has been investigated. La nanoparticle-coated nanofibers succeeded to locally cease the growth of all tested microbes. Each disc succeeded to stop the growth of tested microbes at the boundaries between the disc and the plates’ surfaces, forming clear zones with 7 mm diameter. It is worth mentioning that La nanoparticle-coated nanofibers showed the same pattern of antimicrobial activity against all tested microbes. The ability of prepared nanoparticle-nanofiber hybrid to affect the microbes locally is definitely promising for biomedical applications. These results would support the coexistence of the microbes and their antimicrobial agent at the same location and hence improve the overall microbe drug interaction process. Moreover, this kind of antimicrobial agent localization would prevent the probability of its migration to other sites inside the body that would help to avoid the expected subsidiary complications. It would be recommended that these nanoparticle-coated nanofibers are used as wound dressing for skin injuries.
La(III) nanocomplexes with different organic ligands were synthesized and characterized by different techniques. In addition to the nanosize was proved by different techniques also. All prepared metal complexes were screened against different human cell lines. It was found that we were able to identify new potent and selective anticancer compounds. Also, one of these nanocomplexes was tested as wound dressing which is recommended to be used as local chemotherapy for skin injuries.
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