The inappropriate use of antimicrobials has resulted in the selection of resistant strains. Thus, a great number of studies have focused on the investigation of new antimicrobial agents. The use of zinc oxide nanoparticles (ZnO NPs) to optimise the fight against microbial resistance has been receiving increased attention due to the non-specific activity of inorganic antimicrobial agents. The small particle size and the high surface area of ZnO NPs can enhance antimicrobial activity, causing an improvement in surface reactivity. In addition, surface modifiers covering ZnO NPs can play a role in mediating antimicrobial activity since the surface properties of nanomaterials alter their interactions with cells; this may interfere with the antimicrobial effect of ZnO NPs. The possibility of using surface modifiers with groups toxic to microorganisms can improve the antimicrobial activity of ZnO NPs. Understanding the exact toxicity mechanisms is crucial to elucidating the antimicrobial activity of ZnO NPs in bacteria and fungi. Therefore, this review aims to describe the mechanisms of ZnO NPs toxicity against fungi and bacteria and how the different structural and physical-chemical characteristics of ZnO NPs can interfere in their antimicrobial activity.

Pharmaceutical design has enabled important advances in the prevention, treatment, and diagnosis of diseases. The use of nanotechnology to optimize the delivery of drugs and diagnostic molecules is increasingly receiving attention due to the enhanced efficiency provided by these systems. Understanding the structures of nanocarriers is crucial in elucidating their physical and chemical properties, which greatly influence their behavior in the body at both the molecular and systemic levels. This review was conducted to describe the principles and characteristics of techniques commonly used to elucidate the structures of nanocarriers, with consideration of their size, morphology, surface charge, porosity, crystalline arrangement, and phase. These techniques include X-ray diffraction, small-angle X-ray scattering, dynamic light scattering, zeta potential, polarized light microscopy, transmission electron microscopy, scanning electron microcopy, and porosimetry. Moreover, we describe some of the commonly used nanocarriers (liquid crystals, metal–organic frameworks, silica nanospheres, liposomes, solid lipid nanoparticles, and micelles) and the main aspects of their structures.

Tuberculosis (TB) is a disease caused by Mycobacterium tuberculosis. Cessation of treatment before the recommended conclusion may lead to the emergence of multidrug-resistant strains. The aim of this study was to develop nanostructured lipid carriers (NLCs) for use in the treatment of M. tuberculosis. The NLCs comprised the following lipid phase: 2.07% polyoxyethylene 40 stearate, 2.05% caprylic/capric triglyceride, and 0.88% polyoxyl 40 hydrogenated castor oil; the following aqueous phase: 3.50% poloxamer 407 (F1–F6), and 0.50% cetyltrimethylammonium bromide (F7–F12); and incorporated the copper(II) complexes [CuCl₂(INH)₂]·H₂O (1), [Cu(NCS)₂(INH)₂]·5H₂O (2), and [Cu(NCO)₂(INH)₂]·4H₂O (3) to form compounds F11.1, F11.2, and F11.3, respectively. The mean diameter of F11, F11.1, F11.2, and F11.3 ranged from 111.27±21.86 to 134.25±22.72 nm, 90.27±12.97 to 116.46±9.17 nm, 112.4±10.22 to 149.3±15.82 nm, and 78.65±6.00 to 122.00±8.70 nm, respectively. The polydispersity index values for the NLCs ranged from 0.13±0.01 to 0.30±0.09. The NLCs showed significant changes in zeta potential, except for F11.2, with F11, F11.1, F11.2, and F11.3 ranging from 18.87±4.04 to 23.25±1.13 mV, 17.03±1.77 to 21.42±1.87 mV, 20.51±1.88 to 22.60±3.44 mV, and 17.80±1.96 to 25.25±7.78 mV, respectively. Atomic force microscopy confirmed the formation of nanoscale spherical particle dispersions by the NLCs. Differential scanning calorimetry determined the melting points of the constituents of the NLCs. The in vitro activity of copper(II) complex-loaded NLCs against M. tuberculosis H₃₇R_v showed an improvement in the anti-TB activity of 55.4, 27.1, and 41.1 times the activity for complexes 1, 2, and 3, respectively. An in vivo acute toxicity study of complex-loaded NLCs demonstrated their reduced toxicity. The results suggest that NLCs may be a powerful tool to optimize the activity of copper(II) complexes against M. tuberculosis.