Naked Selenium Nanoparticles for Antibacterial and Anticancer Treatments

Abstract

Currently, antibiotic resistance and cancer are two of the most important public health problems killing more than ∼1.5 million people annually, showing that antibiotics and current chemotherapeutics are not as effective as they were in the past. Nanotechnology is presented here as a potential solution. However, current protocols for the traditional physicochemical synthesis of nanomaterials are not free of environmental and social drawbacks, often involving the use of toxic catalysts. This article shows the production of pure naked selenium nanoparticles (SeNPs) by a novel green process called pulsed laser ablation in liquids (PLAL). After the first set of irradiations, another set was performed to reduce the size below 100 nm, which resulted in a colloidal solution of spherical SeNPs with two main populations having sizes around ∼80 and ∼10 nm. The particles after the second set of irradiations also showed higher colloidal stability. SeNPs showed a dose-dependent antibacterial effect toward both standard and antibiotic-resistant phenotypes of Gram-negative and Gram-positive bacteria at a range of concentrations between 0.05 and 25 ppm. Besides, the SeNPs showed a low cytotoxic effect when cultured with human dermal fibroblasts cells at a range of concentrations up to 1 ppm while showing an anticancer effect toward human melanoma and glioblastoma cells at the same concentration range. This article therefore introduces the possibility of using totally naked SeNPs synthesized by a new PLAL protocol as a novel and efficient nanoparticle fabrication process for biomedical applications.

Figure 1

Setup for synthesis of Se NP by PLAL (a) initial irradiation and (b) ice bath post irradiation to control size and agglomeration.

Figure 2

(a) UV–visible spectra of the colloidal solutions shown in the photo, which is the inset. Inset: photo of colloidal solutions from 100 to 5000 Hz from left to right (credit: Tina Hesabizadeh). (b) Various concentrations of selenium in the colloidal solutions synthesized by PLAL at various repetition rates. The maximum was reached at 3028 ± 58 Hz. The irradiation time was set to 5 min for all samples.

Figure 3

(a) Size distribution obtained by DLS for the selenium nanoparticles synthesized at 3000 Hz according to the synthesis protocol shown in Figure 1a. The size distribution is centered at 144 ± 46 nm. (b) Zeta potential was measured to be −24 ± 16 mV, meaning that the colloidal solution was not stable with time. (c) SEM image of the selenium nanoparticles synthesized at 3000 Hz according to the synthesis protocol as shown in Figure 1a. The spherical shape is not well-defined after the first 5 min set of irradiations. (d) Size distribution obtained by DLS for the selenium nanoparticles synthesized at 3000 Hz; the size distribution is centered at 43 ± 20 nm. (e) Zeta potential was measured to be 66 ± 3 mV, meaning that the colloidal solution is going to be stable with time. (f) SEM image of the selenium nanoparticles synthesized after two sets of irradiations at 3000 Hz (first set of irradiation performed within a rounded flask cuvette, second set of irradiation performed within a test tube surrounded with ice). The irradiation time was kept to 5 min for both sets of irradiations.

Figure 4

(a) TEM image of a representative selenium nanoparticle with its size ∼85 nm, and (b) its corresponding diffraction pattern revealing the amorphous structure of the selenium nanoparticle. (c) Raman spectra performed on selenium nanoparticles deposited on a silicon wafer confirming the amorphous structure of the selenium nanoparticles.

Figure 5

(a) Size histogram of selenium nanoparticles analyzed by AFM (Inset: AFM image, which is insetted into the size distribution on the x–y scale) and (b) by high magnification TEM (scale bar is 10 nm) showing some selenium quantum dots.

Figure 6

Colony counting assay of (a) MRSA, (b) MDR E. coli, (c) S. epidermidis, and (d) P. aeruginosa for 8 h in the presence of different concentrations of SeNPs. All values represent the mean ± standard deviation. *p < 0.05, **p < 0.01(compared to controls).

Figure 7

SEM micrographs of (a, c) control MDR E. coli and MRSA and (b, d) bacteria after treatment with SeNPs.

Figure 8

(a) HDF, (b) melanoma and (c) glioblastoma cells in the presence of SeNPs at concentrations ranging from 0.05–1.00 ppm. n = 3. All values represent the mean ± standard deviation. *p < 0.05, **p < 0.01(compared to controls).

Figure 9

ROS study of SeNPs analysis. n = 3. Data is represented as mean ± SD; *p < 0.05, **p < 0.01(compared to controls).