Health Risks and Regulation of Nanoparticles

Health Risks of Nanoparticles

  • Nanoparticles can have detrimental effects on human health.

Asbestos

  • Asbestos is a naturally occurring rock mineral used commercially since the 18th century.
  • It was valued for its fire retardant and insulation properties.
  • Asbestos consists of pliable fibers that can be separated into strands for various uses.
  • It was predominantly used in the building and construction industries from the early 1900s to the mid-1970s.

Asbestos as a Health Risk

  • 1907: The first case of asbestosis was described.
  • 1924: Confirmation of the relationship between asbestos exposure and pulmonary fibrosis in British workers.
  • 1950s: Association established between occupational exposure to asbestos and lung cancer or mesothelioma.
  • 1966: Average latency interval for lung cancer development estimated at 20 years, and 25 to 50 years for mesothelioma.
  • 2004: Asbestos was completely banned in Ireland.

Lag Time and Mortality

  • Asbestos mortality peaked around 2018, reflecting heavy exposure in the 1970s.
  • There is a long lag time between exposure and the onset of disease.
  • Long delays in disease onset make assessing health risks of new nanomaterials challenging.

Vaping

  • E-cigarettes produce nanoparticles that deposit in the lungs.
  • The chemical composition and size of these particles are largely unknown, depending on the vaping device and liquid.
  • The actual health risks of vaping are not well understood.

Diseases Associated with Nanoparticle Exposure

  • Chronic inflammation is a common reaction to nanoparticle exposure.

Toxicity of Nanoparticles

  • Novel properties emerge at the nanoscale, including mechanical, catalytic activity, conductivity, reactivity, optical features, and electromagnetic properties.
  • Nanoparticles show increased uptake and interaction with biological tissues, which can alter biological functions.

Nanoscale Effects on Properties

  • Electrical: Increased electrical conductivity in ceramics and magnetic nanocomposites; increased electric resistance in metals.
  • Magnetic: Increased magnetic coercivity up to a critical grain size; superparamagnetic behavior.
  • Mechanical: Improved hardness and toughness of metals and alloys; ductility and superplasticity of ceramics.
  • Optical: Spectral shift of optical absorption and fluorescence properties; increased quantum efficiency of semiconductor crystals.
  • Catalytic: Better catalytic efficiency through higher surface-to-volume ratio.
  • Sterical: Increased selectivity; hollow spheres for specific drug transportation and controlled release.
  • Biological: Increased permeability through biological barriers (membranes, blood-brain barrier, etc.); improved biocompatibility.

Surface-to-Volume Ratio

  • Small particles collectively have a much larger surface area than a single large particle of the same mass.
  • Interactions take place at the particle's surface, nanoparticles interact more strongly with biological molecules.

Hydrophobicity and Immune Response

  • Hydrophobic nanoparticle coatings can induce a stronger immune response.
  • Splenocytes exposed to gold nanoparticles (AuNP) with different hydrophobic coatings showed that more hydrophobic coatings induced a stronger immune response.

Macrophages and Silicon Nanoparticles

  • Macrophages respond adversely to amorphous silicon nanoparticles.
  • Nanoparticle uptake by macrophages can change their transcriptional activity and cell proliferation and induce pro-inflammatory signalling.

Nanoparticle Surface Chemistry

  • When nanoparticles contact body fluids, proteins will adsorb to their surface, unless the nanoparticles repel them.
  • These adsorbed proteins might be recognized by cells and evoke responses.

Nanoparticle Corona

  • The nanoparticle 'corona' makes it difficult to reliably assess nanoparticle toxicity.
  • Slightly different fabrication processes or the presence of different co-factors (serum proteins, etc.) can lead to different experimental outcomes in vitro.
  • In vivo studies under well-controlled settings are needed to obtain pathologically relevant data.

Regulation of Nanoparticles

  • The uncertainty of nanomaterial toxicity led to new labeling guidelines using '(nano)'.

Recent Regulations

  • Toxicity depends on the physical characteristics of the material (nanometer size) and its formulation.
  • Inhaled particulate dusts can be toxic (tolerable dose to be determined).
  • The same particles embedded in solids and liquids are not toxic.
  • No studies showed toxicity when used as a food additive.

Titanium Dioxide

  • Titanium dioxide (E171) is no longer considered safe when used as a food additive.

Testing Procedures

  • Agreement has been reached on testing procedures for nanoparticles.

Biomedical Applications of Nanoparticles

  • Nanoparticles can be used to benefit human health.

Nanomedicine

  • The ability of nanoparticles to interact with biological molecules and cells and overcome natural barriers is valuable for medical applications.
  • Nanomedicine is defined as: "The science and technology of diagnosing, treating, preventing disease and relieving pain of traumatic injury by preserving and improving human health, using molecular tools and molecular knowledge of the human body."

Medical Applications

  • Drug delivery.
  • Therapy.
  • Diagnosis and sensing.
  • Medical imaging.

Drug Carrier Systems

  • Most common nanoparticles for drug delivery are formed by self-assembly from amphiphilic building blocks (molecules with hydrophilic and hydrophobic parts) that can incorporate or carry drugs and display certain molecules on their surface.

Passive vs Active Drug Targeting

  • Passive: Accumulation in target tissue.
  • Active: Specific recognition & uptake by malignant cells.

Passive Targeting

  • Endothelial cells lining blood vessels in tumors are more permeable than in healthy tissue.
  • The idea is to design nanocarriers of appropriate size that exploit the Enhanced Permeation and Retention (EPR) effect.
  • Typical particle sizes are in the range of 10−500nm10-500 nm.
  • This leads to accumulation in tumor tissue and better selectivity versus healthy tissue.

Active Targeting

  • Active targeting is based on the attachment of specific ligands to the surface of pharmaceutical carriers to recognize and bind pathological cells, tissue structures, or allow localization and uptake of the drug carrier.

Extended Summary

  • Humans have always been exposed to tiny particles via natural processes, and our bodily systems are adapted to protect us from these intruders.
  • The reticuloendothelial system actively neutralizes and eliminates foreign matter, including viruses and nonbiological particles.
  • Technological advancement has increased the proportion of nanometer-sized particles and expanded the variety of chemical compositions in particulate pollution.
  • Epidemiological studies show a strong correlation between particulate air pollution levels and various adverse health outcomes.
  • Adverse effects of nanoparticles depend on individual factors, exposure, and nanoparticle characteristics.
  • Inhaled nanoparticles are less efficiently removed than larger particles, causing lung damage, and can translocate through the body.
  • The minute size of nanoparticles allows them to penetrate basic biological structures, disrupting their normal function.
  • Toxic effects include tissue inflammation and altered cellular redox balance toward oxidation.
  • Ongoing and expanded study of "nanotoxicity" is necessary.
  • Intelligent design of materials and devices is needed to derive the benefits of these new technologies while limiting adverse health impacts.
  • Reduction in fossil fuel combustion and limiting deforestation and desertification would have a large impact on global human exposure to nanoparticles.