This study presents the influence of the primary formulation parameters on the formation of poly-dl-lactic-co-glycolic nanoparticles by the emulsification-solvent evaporation, and the nanoprecipitation techniques.

The use of polymeric nanoparticles for the control release of photosensitizer compounds such as methylene blue represents a promising option for cancer treatment. Methylene blue (MB) has been of great interest in many areas of clinical medicine, from neurological disorders to cancer chemotherapy [1][2]. It can be used in photodynamic therapy, which consists on the application of MB in the area of interest, and then activated by light at 665 nm producing reactive oxygen species that leads to the death of the target cell via oxidative damage. Polymeric nanoparticles loaded with methylene blue (MB-PNP) were prepared by using a combined emulsification technique [4][5]. Briefly, MB is dissolved in deionized water and into a DCM solution containing MB and PLGA. The mixture is emulsified at 22% of amplitude (26.5 µm) by sonication. Next, an aqueous solution of 5% w/v PVA is added into the mixture and a second emulsification is carried during at 75% amplitude (90 µm). The solvent is evaporated under magnetic stirring, at room temperature. MB-PNPs are washed by three centrifugation cycles and freeze-dried for further characterization. All experiments were performed by triplicate.Nanoparticle size distribution and zeta potentials were measured using a zetasizer Nano ZS equipment (Malvern) by dynamic light scattering and laser Doppler electrophoresis, respectively. Average values of particle size obtained were 180 nm with 0.030 polydispersity index (PDI) and 190 nm with 0.109 PDI for blank PNP and 12% TDL MB-PNP respectively. Zeta potential values obtained were -31.2 mV for blank-PNP and -18.2mV for MB-PNP. This difference in superficial charge can be attributed to the presence of MB on the surface of the nanoparticle. Similar work has been reported in literature where MB is encapsulated in PLGA using different encapsulation methods, and sizes range from 190 to 220 nm, with zeta potentials ranging between -38 mV and -17.5 mV [3]. When encapsulating 2.5% TDL, authors have obtained 220 to 266 nm diameters with PDI values of 0.19 and 0.4 [1]. Other materials have also been used to encapsulate MB such as silica nanoparticles, resulting in diameters of particle of 105 nm, with zeta potentials between -44 and -29 mV [5]. Surface morphology of MB-PNP was analysed by scanning electron microscopy (JEOL) (Figure 1). The drug loading (DL) for MB-PNP was 0.97 %, resulting in a 8.06 % encapsulation efficiency (EE). Cannavà et al. obtained drug loadings values of 0.52 % to 1.13 % and encapsulation efficiencies of 3.13 % to 6.75 % [1]. These values are comparable to the ones obtained in this work. Encapsulation efficiency depends on the amount of drug used at the beginning of the formulation, meaning that less MB was used in the formulation in order to obtain the drug load desired.To evaluate in vitro MB release from MB-PNPs, the dialysis method is used [1]. MB concentrations were quantified by spectrometry at 665 nm using a calibration curve. During the study, the amount of MB released in the initial burst stage was 21 µg, which corresp...

The encapsulation of 1,10-epoxyparthenolide (EP) in polymeric nanoparticles could contribute to the development of novel treatments for tuberculosis (TB). TB caused by Mycobacterium tuberculosis, is one of the most devastating bacterial diseases to affect humans [1]. Although an effective therapeutic regimen is available, patient non-compliance results in treatment failure as well as the emergence of drug resistance [2]. Due to the appearance of resistant strains, new alternatives have been sought for the treatment of this disease, in this context, new compounds from plants with antimicrobial potential have been investigated. EP is a compound isolated from the plant Ambrosia confertiflora, which is responsible for the antimycobacterial activity of this plant [3]. PLGA nanoparticles loaded with EP (EP-PNP) were prepared by using a single emulsification technique followed by solvent evaporation [4]. Briefly, 50 mg of PLGA and 2.5 mg of EP were dissolved in 5 mL of dichloromethane (DCM). Next, 25 mL of aqueous solution of 3% w/v poly(vinyl alcohol) was added to the organic phase. The mixture was emulsified at 75% of amplitude for 1 minute. The organic solvent was evaporated at room temperature (25°C), under magnetic stirring. Then, the solution was washed by three centrifugation cycles. After washing, particles were characterized, freeze-dried and stored for further use.

The use of biodegradable polymers for the nanoencapsulation of bioactive compounds represents a promising option for a wide range of applications. Poly-dl-lactic-co-glycolic acid (PLGA) is one of the most successfully used biodegradable polymers in nanomedicine research. One of the reasons of that is because it degrades in the body to biodegradable metabolites; also, practically any hydrophobic or hydrophilic compound could be considered for encapsulation in PLGA nanoparticles (PNP) [1,2]. These PNP could be used as nanocarriers for different compounds in the treatment of brucellosis. Brucellosis is a disease caused by intracellular bacteria of the genus Brucella, a disease which eradication is challenging. Thus, a good strategy to treat this infection is the use of antibiotic nanocarriers which, could prolong the release of them while maintaining a desired concentration on the target site [3]. In the present work, the encapsulation of oxytetracycline hydrochloride (OTC) in PNP (OTC-PNP) was evaluated. The formulation parameters in the encapsulation of OTC by the solvent double-emulsification technique were analyzed.PNP and OTC-PNP were synthesized following the solvent double-emulsification method [4,5]. Briefly, a specific amount of OTC is dissolved in 0.5 mL of deionized water and then added to 5 mL of dichloromethane (DCM) containing 50 mg of PLGA. The mixture was emulsified by sonication for 1 min at 22% amplitude (26.5 µm), then 25 mL of an aqueous solution of 3% w/v poly(vinyl alcohol) (PVA) were added. The mixture was emulsified again by sonication during 1 min at 75% amplitude (90 µm) by using a QSonic 500 sonicator under an ice bath. After the emulsification process, the organic solvent was removed by evaporation at room temperature using magnetic stirring at low speed. Finally, nanoparticles were washed using three centrifugation cycles of 20 min at 37565*g. Particle size, polydispersity index and zeta potential were measured with the Zetasizer Nano ZS. The measures of nanoparticles size were performed by dynamic light scattering (DLS) and the ones for zeta potential by laser Doppler electrophoresis. Size results presented in Fig. 1 not shown significant differences for PNP and OTC-PNP. A low polydispersity index (PDI) for both preparations was found, indicating that the size distribution is homogeneous. Fig. 2 presented zeta potential values around -20 mV for both preparations, which is related to a fair stability. A summary of these results is presented in Table 1.Drug loading (DL) and encapsulation efficiency (EE) were obtained by the determination of OTC concentrations using UV-Vis spectroscopy at 362 nm with a calibration curve prepared in 10 mM phosphate buffer saline at pH 7.4. DL is the actual amount of OTC encapsulated per mass of nanoparticles, resulting in 0.33±0.1%. EE obtained was 3.3±0.1% which is described as percent of OTC encapsulated in OTC-PNP with respect to the amount of OTC initially added. Such relatively low encapsulation could be attributed to the diffusion of water-soluble dru...