In the last few decades, the vast potential of nanomaterials for biomedical and healthcare applications has been extensively investigated. Several case studies demonstrated that nanomaterials can offer solutions to the current challenges of raw materials in the biomedical and healthcare fields. This review describes the different nanoparticles and nanostructured material synthesis approaches and presents some emerging biomedical, healthcare, and agro-food applications. This review focuses on various nanomaterial types (e.g., spherical, nanorods, nanotubes, nanosheets, nanofibers, core-shell, and mesoporous) that can be synthesized from different raw materials and their emerging applications in bioimaging, biosensing, drug delivery, tissue engineering, antimicrobial, and agro-foods. Depending on their morphology (e.g., size, aspect ratio, geometry, porosity), nanomaterials can be used as formulation modifiers, moisturizers, nanofillers, additives, membranes, and films. As toxicological assessment depends on sizes and morphologies, stringent regulation is needed from the testing of efficient nanomaterials dosages. The challenges and perspectives for an industrial breakthrough of nanomaterials are related to the optimization of production and processing conditions.

Nanomaterials are materials with one or more nanoscale dimensions (internal or external) (i.e., 1 to 100 nm). The nanomaterial shape, size, porosity, surface chemistry, and composition are controlled at the nanoscale, and this offers interesting properties compared with bulk materials. This review describes how nanomaterials are classified, their fabrication, functionalization techniques, and growth-controlled mechanisms. First, the history of nanomaterials is summarized and then the different classification methods, based on their dimensionality (0–3D), composition (carbon, inorganic, organic, and hybrids), origin (natural, incidental, engineered, bioinspired), crystal phase (single phase, multiphase), and dispersion state (dispersed or aggregated), are presented. Then, the synthesis methods are discussed and classified in function of the starting material (bottom-up and top-down), reaction phase (gas, plasma, liquid, and solid), and nature of the dispersing forces (mechanical, physical, chemical, physicochemical, and biological). Finally, the challenges in synthesizing nanomaterials for research and commercial use are highlighted.

Carbon nanomaterials (CNMs) have received tremendous interest in the area of nanotechnology due to their unique properties and flexible dimensional structure. CNMs have excellent electrical, thermal, and optical properties that make them promising materials for drug delivery, bioimaging, biosensing, and tissue engineering applications. Currently, there are many types of CNMs, such as quantum dots, nanotubes, nanosheets, and nanoribbons; and there are many others in development that promise exciting applications in the future. The surface functionalization of CNMs modifies their chemical and physical properties, which enhances their drug loading/release capacity, their ability to target drug delivery to specific sites, and their dispersibility and suitability in biological systems. Thus, CNMs have been effectively used in different biomedical systems. This review explores the unique physical, chemical, and biological properties that allow CNMs to improve on the state of the art materials currently used in different biomedical applications. The discussion also embraces the emerging biomedical applications of CNMs, including targeted drug delivery, medical implants, tissue engineering, wound healing, biosensing, bioimaging, vaccination, and photodynamic therapy.

Intracellular concentrations of isoniazid and rifabutin resulting from administration of inhalable microparticles of these drugs to phorbol-differentiated THP-1 cells and the pharmacokinetics and biodistribution of these drugs upon inhalation of microparticles or intravenous administration of free drugs to mice were investigated. In cultured cells, both microparticles and dissolved drugs established peak concentrations of isoniazid (∼1.4 and 1.1 μg/10 ⁶ cells) and rifabutin (∼2 μg/ml and ∼1.4 μg/10 ⁶ cells) within 10 min. Microparticles maintained the intracellular concentration of isoniazid for 24 h and rifabutin for 96 h, whereas dissolved drugs did not. The following pharmacokinetic parameters were calculated using WinNonlin from samples obtained after inhalation using an in-house apparatus (figures in parentheses refer to parameters obtained after intravenous administration of an equivalent amount, i.e., 100 μg of either drug, to parallel groups): isoniazid, serum half-life ( t _1/2 ) = 18.63 ± 5.89 h (3.91 ± 1.06 h), maximum concentration in serum ( C _max ) = 2.37 ± 0.23 μg·ml ⁻¹ (3.24 ± 0.57 μg·ml ⁻¹ ), area under the concentration-time curve from 0 to 24 h (AUC _0-24 ) = 55.34 ± 13.72 μg/ml ⁻¹ h ⁻¹ (16.64 ± 1.80 μg/ml ⁻¹ h ⁻¹ ), and clearance (CL) = 63.90 ± 13.32 ml·h ⁻¹ (4.43 ± 1.85 ml·h ⁻¹ ); rifabutin, t _1/2 = 119.49 ± 29.62 h (20.18 ± 4.02 h), C _max = 1.59 ± 0.01 μg·ml ⁻¹ (3.47 ± 0.33 μg·ml ⁻¹ ), AUC _0-96 = 109.35 ± 14.78 μg/ml ⁻¹ h ⁻¹ (90.82 ± 7.46 μg/ml ⁻¹ h ⁻¹ ), and CL = 11.68 ± 7.00 ml·h ⁻¹ (1.03 ± 0.11 ml·h ⁻¹ ). Drug targeting to the lungs in general and alveolar macrophages in particular was observed. It was concluded that inhaled microparticles can reduce dose frequency and improve the pharmacologic index of the drug combination.

To investigate whether inhalable microparticles containing two anti-tuberculosis agents, isoniazid and rifampicin, evoke host-defence strategies in macrophages in addition to targeting the incorporated drugs. Microparticles were prepared by spray-drying a homogeneous solution of drugs and poly(lactic acid) (PLA; apparent viscosity 1.1 cP). Four parts PLA and three parts rifampicin were dissolved in dichloromethane. One part isoniazid was dissolved in methanol. The two solutions were mixed in the ratio 22 : 3 at which none of the solutes precipitated. These were administered as ‘nose-only’ inhalations to mice or exposed to cultured J774 mouse macrophages. Targeting to lung macrophages was investigated by transmission electron microscopy. Reactive oxygen species (ROS) were estimated by a cytochrome c assay and flow cytometry. Reactive nitrogen intermediates (RNI) were assayed using Griess reagent. Cytokines in culture supernatants were estimated by ELISA. Treatment with inhalable microparticles targeted lung macrophages in vivo and induced intense Golgi activity in the vicinity of microparticle-containing phagosomes. Microparticles induced a respiratory burst involving NADPH oxidase and enhanced NO production by infected macrophages. Microparticle-induced NADPH oxidase activation required optimal calcium ions. Microparticles efficiently induced tumour necrosis factor-α (TNF-α) secretion by macrophages recovered from infected mice. Microparticle phagocytosis induces responses in infected murine macrophages that are indicative of activation of innate bactericidal mechanisms, and are inimical to bacterial survival. It is likely that such responses augment straightforward drug action on the bacterium and contribute to the unexpectedly high efficacy of microparticles in experimental tuberculosis.