science

Sonodynamic therapy

Sonodynamic therapy is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Sonodynamic therapy rather than just read about it. In short: Sonodynamic therapy (SDT) is a noninvasive treatment, often used for tumor irradiation, that utilizes a sonosensitizer and the deep penetration of ultrasound to treat lesions of varying depths by reducing target cell number and preventing future tumor growth. Many existing cancer treatment strategies cause systemic toxicity or cannot penetrate tissue deep enough to reach the entire tumor; however, emerging ultrasoun…

Key takeaways

Sonodynamic therapy belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Sonodynamic therapy to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Sonodynamic therapy from memory before moving on to harder problems.

Reference excerpt

Sonodynamic therapy (SDT) is a noninvasive treatment, often used for tumor irradiation, that utilizes a sonosensitizer and the deep penetration of ultrasound to treat lesions of varying depths by reducing target cell number and preventing future tumor growth. Many existing cancer treatment strategies cause systemic toxicity or cannot penetrate tissue deep enough to reach the entire tumor; however, emerging ultrasound stimulated therapies could offer an alternative to these treatments with their increased efficiency, greater penetration depth, and reduced side effects. Sonodynamic therapy could be used to treat cancers and other diseases, such as atherosclerosis, and diminish the risk associated with other treatment strategies since it induces cytotoxic effects only when externally stimulated by ultrasound and only at the cancerous region, as opposed to the systemic administration of chemotherapy drugs.

Reactive oxygen species (ROS) are an essential component of SDT as they provide the cytotoxicity of sonodynamic therapy; they are produced when ultrasound is coupled with a sensitizing drug and molecular oxygen. Without ultrasound, the drug is not toxic. However, once the drug is exposed to ultrasound and molecular oxygen, it becomes toxic. Photodynamic therapy, from which sonodynamic therapy was derived, uses a similar mechanism. Instead of ultrasound, light is used to activate the drug. SDT allows the ultrasound to reach deeper into the tissue (to about 30 centimeters) compared to photodynamic therapy (PDT) since it can be highly focused. This increased penetration depth ultimately means that SDT can be utilized to treat deeper, less accessible tumors and is more cost-effective than PDT. Photodynamic therapy can be used in combination with sonodynamic therapy and is expanded upon in the Applications section of this article. Sonodynamic therapy can be used synergistically with other therapeutic methods such as drug-loaded microbubbles, nanoparticles, exosomes, liposomes, and genes for improved efficacy. Currently, SDT does not have any clinical products and acts as an adjuvant for the aforementioned therapeutic methods, but it has been explored for use in atherosclerosis and cancer treatment to reduce tumor size in breast, pancreas, liver, and spinal sarcomas.

Mechanism of Action

The mechanism of action for sonodynamic therapy is the use of low-intensity ultrasound through the use of focused mechanical waves to create a cytotoxic effect. However, SDT itself is non-thermal, non-toxic, and is able to non-invasively penetrate deep into tissue compared to other delivery methods such as photodynamic therapy. SDT is often performed alongside the use of a sonosensitizer such as porphyrin, phthalocyanines, xanthenes, and antitumor drugs. Ultrasound waves are also classified as acoustic waves, and the effect they have on the tissue of application can be described by a process called cavitation. Cavitation occurs as a specific interaction between ultrasound and aqueous surroundings and causes gas bubbles to break upon exposure to particular ultrasonic parameters, thus promoting penetration of the therapeutic into the biological tissues by generating cavities near the edge of the membrane. Cavitation can be broken down into stable and inertial cavitation. In stable cavitation, the oscillation of gas bubbles causes the environmental media to intermix. In inertial cavitation, gas bubbles increase in volume and almost reach their resonance volume, swelling before aggressively collapsing. The implosion of vesicles results in a drastic temperature and pressure change, thereby increasing the cell membrane's permeability to various drugs. Microbubbles are created by the acoustic waves from the ultrasound that expand and collapse, releasing energy, bringing the sonosensitizer into an excited state, and generating a ROS. The cavitation of this gas bubble can form the ROS with different methodologies such as sonoluminescence and pyrolysis. Apoptosis results from the formation of ROS and mechanical forces of SDT through membrane disruption in a process called lipid peroxidation. Necrosis is also a potential result of SDT. The influence of sonoluminescence on SDT and ROS has not been fully elaborated within literature. Currently, it is understood that sonoluminescence allows the emission of light upon bubble collapse which can activate sensitizers. A study by Hachimine et al. highlights the use of SDT as a method to activate a low photosensitive sonosensitizer, DCPH-P-Na(I), for cancer that is too deep within the tissue to combat utilizing PDT without skin irritation. Pyrolysis raises the surrounding temperature, enhances the cavitation process, breaks down the sensitizer, generating free radicals, and the free radicals interact within their environment to generate ROS. For both methods, the importance of the singlet oxygen compared to the hydroxyl radical to induce cytotoxicity has been highlighted. While other studies have found the singlet oxygen to not have a substantial effect. Overall, both of these methodologies lack significant breadth in literature to fully explain their role in ROS formation. However, literature has shown success in their analysis and application.

Sonoluminescence

Two primary mechanisms of ROS generation exist in sonodynamic therapy: sonoluminescence and pyrolysis. Sonoluminescence occurs when ultrasound produces light after irradiating an aqueous solution The exact mechanism with which light is produced remains unclear. However, it is suggested that inertial cavitation is a key element for this process. Other studies also indicate the potential role of stable cavitation

Pyrolysis Pyrolysis is believed to occur when inertial cavitation induces an extreme temperature increase, degrades the sonosensitizers, thus producing free radicals that can react and ultimately produce ROS necessary for SDT. The localized temperature increase assists in the inertial cavitation and breakdown of the sonosensitizer in order to create ROS. The pyrolysis within the cavitation bubbles will produce H+ and OH- via weak bonding within the solute molecule.

Lipid Peroxidation

… excerpt ends here. Continue reading the full article.

Illustrations

Sonodynamic therapy: Cavitation bubble implosion — Cavitation bubble implosion

Worked examples

Example 1 — a first encounter with Sonodynamic therapy

Start with the simplest possible case. Write down what Sonodynamic therapy claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Sonodynamic therapy before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Sonodynamic therapy ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Sonodynamic therapy

In research: Sonodynamic therapy appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Sonodynamic therapy in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Sonodynamic therapy is common in secondary-school and first-year university syllabi. It links to neighbouring topics Medical treatments, so understanding it makes those chapters shorter.
In everyday life: Look for Sonodynamic therapy outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Sonodynamic therapy in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Sonodynamic therapy means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Sonodynamic therapy out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Sonodynamic therapy in simple terms?

Why does Sonodynamic therapy matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Sonodynamic therapy?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Sonodynamic therapy.