Medical Nanotechnology and Nanomedicine Study Guide

Foundations and Definitions of Nanotechnology and Nanomedicine

Definition of Nanotechnology: Nanotechnology is the branch of science and engineering dedicated to designing, producing, and manipulating structures at the nanoscale. These structures typically involve dimensions and tolerances of less than $100\,nm$ .
Scale of Nanoparticles: To understand the extreme smallness of the nanoscale, compare the following items and devices (measured in nanometres, $nm$ ): * Natural/Biological Entities: * Water: $10^{-1}\,nm$ * Glucose: $1\,nm$ * Antibody: $10\,nm$ * Virus: $100\,nm$ * Bacterium: $1,000\,nm$ (or $10^{3}\,nm$ ) * Cancer cell: $10,000\,nm$ to $100,000\,nm$ ( $10^{4}$ to $10^{5}\,nm$ ) * A period (punctuation): $1,000,000\,nm$ ( $10^{6}\,nm$ ) * Tennis ball: $100,000,000\,nm$ ( $10^{8}\,nm$ ) * Nanodevices and Materials: * Nanopores: Approx. $1\,nm$ * Dendrimers: Approx. $10\,nm$ * Quantum dots: Approx. $10\,nm$ * Nanotubes: Approx. $100\,nm$ * Nanoshells: Approx. $100\,nm$
Defining Nanomedicine: * Nanomedicine was first defined in late 1999 and early 2000. * It represents the application of nanotechnology for medical purposes. * It involves the use of nanomaterials for the diagnosis, monitoring, control, prevention, and treatment of diseases. * The specific type of nanomaterial used is strictly dependent on the medical application intended.

Historical Development and Origins

Richard Feynman (1959): * The conceptual birth of nanoscience and nanotechnology is attributed to physicist Richard Feynman. * On December 29, 1959, he delivered a landmark talk entitled "There’s Plenty of Room at the Bottom" at an American Physical Society meeting held at the California Institute of Technology (CalTech). * Feynman described a theoretical process where scientists would eventually manipulate and control individual atoms and molecules, though he did not use the word "nanotechnology" at the time.
Professor Norio Taniguchi (1974): * The term "nanotechnology" was officially coined in 1974 by Professor Norio Taniguchi of the Tokyo University of Science. * Taniguchi used the term to describe ultraprecision machining and semiconductor processes, such as thin film deposition and ion beam milling, which exhibited characteristic control on the order of a nanometre.

Engineering and Dimensionality of Nanomaterials

Engineered Nanomaterials (ENMs): Materials engineered at this size are termed ENMs. They possess unique optical, magnetic, electrical, and physical properties that differ from their bulk counterparts. These emergent properties impact electronic, material sciences, and medicine.
Dimensionality in Nanomedicine: * Zero Dimension (0D): e.g., Graphene quantum dots (GQDs). * One Dimension (1D): e.g., Surface films. * Two Dimensions (2D): e.g., Strands and fibres. * Three Dimensions (3D): e.g., Particles.
Forms and Shapes: Nanomaterials can exist in single, fused, aggregated, or agglomerated forms. Common morphologies include spherical, tubular, and irregular shapes.
Four Major Categories of Nanomaterials: 1. Inorganic-based: Includes metals and metal oxides. 2. Carbon-based: Includes carbon nanotubes and fullerenes. 3. Organic-based: Includes polymers and lipids. 4. Composite-based: Hybrid structures combining different materials.

Carbon-Based Nanoparticles

Carbon Nanotubes (CNTs): * Structure: Graphene sheets rolled into a tube. * Single-walled carbon nanotubes (SWCNTs): Consist of a single layer of graphene. * Multi-walled carbon nanotubes (MWCNTs): Consist of multiple nested layers of graphene.
Fullerenes: * Allotropes of carbon. * Commonly called "buckyballs" due to their spherical, cage-like structure.
Graphene: Another key carbon-based material used in medical sensing and imaging (e.g., Graphene quantum dots).

Polymeric Nanoparticles (PNP)

Composition: Nanosized solid particles consisting of natural or synthetic polymers.
Materials Used: * Natural Polymers: Chitosan, albumin, and heparin. * Synthetic Polymers: * $(N-(2-hydroxypropyl)-methacrylamide)$ copolymer. * $Poly(ethylene\,glycol)$ (PEG). * $Poly(lactic\,acid-glycolic\,acid)$ (PLGA). * $Poly(lactic\,acid)$ (PLA).
Functional Characteristics of PNPs: * Can be biodegradable or non-biodegradable. * Often coated with non-ionic surfactants to minimize immunological reactions. * Drug Loading: Drugs or biomolecules are encapsulated to achieve slow and sustained release at targeted sites.
Subtypes of PNPs: * Polymeric Micelles: Copolymers that spontaneously assemble into core-shell structures in aqueous solutions. Typically consist of a hydrophilic PEG shell and hydrophobic domains (e.g., PLA, poly(l-lysine), poly(beta-amino ester)). * Dendrimers: Highly branched macromolecules (dendrons) emerging from a central core. Loading occurs via hydrogen bonds, hydrophobic interactions, or chemical cross-linkers. * Liposomes: * Spherical vesicles with one or more phospholipid bilayers. * Feature low toxicity and high biocompatibility. * Stealth Liposomes: Coated with polymers (like PEG) to improve colloidal stability and avoid immune detection. * Used widely for drug and gene delivery. * Polymerosomes: Vesicles made of synthetic amphiphilic polymers with attractive properties for biomedical applications.

Magnetic and Metallic Nanoparticles

Synthesis: Prepared from metal precursors via chemical, electrochemical, or photochemical methods.
Structure: Usually comprise a magnetic material (iron, nickel, or cobalt) and a functional chemical component.
Supramagnetic Iron Oxide Nanoparticles (SPIONs): One of the most promising substances for clinical diagnosis and therapy (theranostics).
Theranostics: The integration of therapy and diagnostics. Example: Using PET scan imaging to identify tumour receptors; if targets are visible, a radioactive drug is administered to treat those specific tumours.
History of Magnetic Drug Delivery: * Proposed in the late 1970s by Widder, Senyi, and colleagues (1978). * Mechanism: Drug molecules are attached to magnetic nanomaterials, injected into the body, and guided to the target site using localized magnetic field-gradients. Particles are held at the site until therapy is complete and then removed. * Advantages: High local drug concentration; avoidance of systemic toxic side effects.

Biomedical Applications and Drug Delivery

Broad Applications: Tissue engineering, drug/gene delivery, cancer therapy, bioimaging, and pathogen detection.
Drug Delivery Precision: * Nanoparticles (NPs) deliver drugs in the optimum dosage range, increasing therapeutic efficiency and patient compliance. * $Polyethlyene\,oxide$ (PEO) and $Poly(lactic\,acid)$ (PLA) NPs are promising for intravenous administration.
Cancer Cell Targeting: * Active Targeting: NPs are conjugated to ligands like aptamers, antibodies, or peptides that bind to specific receptors on cancer cells. * Passive Targeting (EPR Effect): The "Enhanced Permeability and Retention" effect allow NPs to naturally accumulate in tumours due to leaky vasculature and poor lymphatic drainage. * Once at the site, NPs enter cells and release encapsulated drugs, potentially inducing signalling mechanisms to eradicate the cancer. * Example: Liposomes combined with the chemotherapeutic drug Doxorubicin are used clinically for adult cancers.

Bioimaging and Innovative Diagnostic Tools

Quantum Dots (QDs): * Inorganic semiconductor molecules that emit strong fluorescent light under ultraviolet (UV) illumination. * Size-Dependent Color: The wavelength (colour) of emitted light depends on the particle size. * Used for precision imaging of organs (e.g., liver) and delivery of anti-cancer drugs, reducing off-target effects of chemotherapy.
Medical Imaging Enhancements: NPs improve MRI, PET, and optical imaging. They act as contrast agents with fewer side effects than traditional agents (e.g., avoiding nephrotoxicity or allergic reactions associated with gadolinium).
Nanodiamonds (NDs): * Single crystal diamonds consisting of carbon. * Chemically inert and biocompatible. * Used as probes for fluorescence imaging and contrast agents for MRI and photoacoustic imaging.
Photoacoustic Imaging (PAI): A non-invasive modality that generates ultrasonic waves by irradiating tissue with a pulsed laser to reconstruct images of light energy absorption.
Smartphone Microscopes: New apps and attachments can detect nanoscale norovirus particles in water by using paper chips with fluorescent polystyrene beads.

Nanorobotics in Medicine

Characteristics: * Current size: $0.5\,nm\text{--}3\,μm$ . * Made of non-toxic materials designed for secretion via the renal clearance system. * Equipped with pressure, chemical, and temperature sensors; magnetic plates; and power sources.
Capabilities: * Can carry drugs to specific sites with $100\%$ accuracy. * Movements monitored by in-built cameras. * Can repair infections or detect damage. * Able to remove solid masses (tumours) with precision, addressing cancers difficult to reach via surgery or radiotherapy.
Applications: Dental surgery, arteriosclerosis, tissue engineering, pharmacokinetics monitoring, and ophthalmology.

Innovative Vaccination and Wound Care

Nanopatch Vaccines (Vaxxas): * Created by Professor Mark Kendall in Australia. * A stamp-sized patch covered in thousands of vaccine-coated silicon microneedles. * Advantages: Painless (needle-free), requires smaller doses for the same immune response, eliminates the need for refrigeration, and is safer for global distribution.
Smart Bandages: * Bioabsorbable hydrogel bandages that dissolve over time. * Embedded nanofibers can contain clotting agents or growth hormones. * Sensors detect infection and trigger the release of antibiotics as needed.

Tissue Engineering (TE)

Definition: Established by Langer and Vacanti in the early 90s as an interdisciplinary field applying engineering and life science principles to develop biological substitutes that restore, maintain, or improve tissue function.
Classic Paradigm: Combining living cells with a support (scaffold) to create a 3D construct functionally equal to natural tissue.
Nanotechnology Role in TE: * Enhances electrical and mechanical properties. * Facilitates DNA transfection and viral transduction. * Example: Silver NPs in nanofibrous scaffolds enhance bone cell growth and provide an antibacterial coating to protect against sepsis and implant malfunction.

Limitations and Toxicity Risks

Cellular Toxicity: The small size and high reactivity of magnetic NPs can induce adverse cellular effects.
Reactive Oxygen Species (ROS): * QDs with inorganic-metal cores can induce ROS formation in vitro and in vivo. * ROS are generated from the NP surface or transition metal contaminants. * Effects of ROS: Oxidize lipids, proteins, and DNA; interfere with cell signalling; and recruit macrophages to release pro-inflammatory cytokines, causing inflammation.

Questions & Discussion

Hydrophobic Drug Delivery Case Study: * Question: A research team is developing a drug delivery system for a hydrophobic anti-cancer compound requiring slow, sustained release over 72 hours specifically at a tumour site. Based on properties, which NP type is MOST appropriate? * Correct Response: C) Polymeric nanoparticles (PNPs). Their biodegradable core-shell micelle architecture encapsulates hydrophobic drugs and enables controlled, sustained release with surface conjugation for tumour targeting.
MRI Contrast Switching Case Study: * Question: A cancer patient with early-stage renal impairment requires MRI monitoring. The oncologist considers replacing gadolinium agents with supramagnetic iron oxide nanoparticles (SPIONs). Which statement justifies this? * Correct Response: B) SPIONs are a safer alternative because gadolinium carries risks of nephrotoxicity and deposition, whereas SPIONs create strong MRI contrast, are biodegradable, and are metabolised through normal iron homeostasis pathways, reducing renal burden.