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Photodynamic Therapy


What is Photodynamic Therapy?

Photodynamic Therapy (PDT) is a treatment that uses special drugs called photosensitizing agents, along with light, to kill cancer cells and treat certain skin condition. These photosensitizing agents only work after they have been activated or “turned on” by specific wavelengths of light.

Depending on which part of the body is being treated, the photosensitizing agent is either injected into the bloodstream or applied directly onto the skin. Over a certain amount of time the drug is absorbed by the cancer cells. Light is then applied to the treatment area using an optical fiber.

The light triggers a photochemical reaction but does not cause any heat damage. Instead, it causes the drug to react with oxygen, which forms a chemical that kills the targeted cells. PDT also helps by destroying blood vessels that feed cancer cells and by alerting the immune system to attack the cancer.

Laserglow offers a wide range of fiber coupled laser light sources that are ideally suited for PDT.

The most common wavelengths used in PDT are between 633nm-760nm (depending on the photosensitizing agent used) with typical fiber coupled output powers between 500mW and 2W.

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Pros and Cons of PDT

Studies have shown that PDT can work as well as surgery or radiation therapy in treating certain kinds of cancers and pre-cancers. It has several advantages over traditional treatments:

  • No long-term side effects when used properly.
  • Less invasive than surgery.
  • Short procedure, most often done outpatient.
  • Can be targeted very precisely.
  • Unlike radiation, PDT can be repeated many times on the same site if needed.
  • Little to no scarring after the site heals.
  • Costs less than traditional cancer treatments.

But PDT has limits too:

  • PDT can only treat areas where light can reach. This means it’s mainly used to treat problems on or just under the skin, or in the lining of organs that can be reached with a light source. Because light can’t travel very far through body tissues, PDT can’t be used to treat large cancers or cancers that have grown deeply into the skin or other organs.
  • PDT can’t be used to treat cancers that have spread to multiple places in the body.
  • The drugs used for PDT leave people very sensitive to light for some time, so special precautions must be taken after the drugs are applied to the body.
  • PDT can’t be used on people who have certain blood diseases, such as any of the porphyrias (a rare group of diseases that affect the skin or nervous system) or people who are allergic to porphyrins. This allergy is rare, but it may happen in those who have gotten porphyrins in the past.



Photosensitizer Properties

The ideal PDT photosensitizer has the following characteristics:

  1. available in pure form, of known chemical composition;
  2. synthesizable from available precursors and easily reproduced;
  3. high singlet oxygen quantum yield (ΦΔ);
  4. strong absorption in the red region of the visible spectrum (λmax = 680–800 nm) with a high extinction coefficient (εmax = 50,000–100,000 M−1 cm−1);
  5. effective accumulation in tumor tissue and possession of low dark toxicity for both photosensitizer and its metabolites;
  6. stable and soluble in the body’s tissue fluids, and easy delivery to the body via injection or other methods;
  7. excreted from the body upon completion of treatment.



Properties of some photosensitizer dyes approved for PDT treatment and used in PDT-related clinical trials:

Compound

Trademark

λmax (nm)
(εmax (M−1cm−1))

ΦΔ

Application

Laserglow Wavelengths Available

Porfimer sodium

Photofrin

632 (3000)

0.89

Canada (1993)—bladder cancer; USA (1995)—esophogeal cancer; USA (1998)—lung cancer; USA (2003)—Barrett’s esophagus; Japan—cervical cancer; Europe, Canada, Japan, USA, UK—endobroncheal cancer

633nm

635nm

5-Aminolevulinic acid (ALA)

Levulan

632 (5000)

0.56

USA (1999)—actinic keratosis

-

Methyl aminolevulinate (MAL)

Metvixia

USA (2004)—actinic keratosis

-

Hexaminolevulinate (HAL)

Cysview

USA (2010)—bladder cancer diagnosis

-

Benzoporphyrin derivative monoacid ring A (BPD-MA)

Visudine

689 (34,000)

0.84

USA (1999)—age-related macular degeneration

690nm

Meta-tetra(hydroxyphenyl)chlorin (m-THPC)

Foscan

652 (35,000)

0.87

Europe-neck and head cancer

650nm – 655nm

Tin ethyl etiopurpurin

Purlytin

664 (30,000)

Clinical trials—breast adenocarcinoma, basal cell carcinoma, Kaposi's sarcoma, age-related macular degeneration

665nm

N-aspartyl chlorin e6 (NPe6)

Laserphyrin, Litx

664 (40,000)

0.77

Japan (2003)-lung cancer

-

2-(1-Hexyloxyethyl)-2-devinyl pyropheophorbide (HPPH)

Photochlor

665 (47,000)

Clinical trials—esophogeal cancer, basal cell carcinoma, lung cancer, Barrett’s esophagus

-

Palladium bacteriopheophorbide (WST09)

Tookad

763 (88,000)

0.50

Phase IV clinical trials for prostate cancer as of Feb 2019

*Showing promising results. Predicted to grow in popularity

760nm

WST11

Stakel

Clinical trials—prostate cancer

-

Motexafin lutetium (Lu-Tex)

Lutrin, Optrin, Antrin

732 (42,000)

Clinical trials—prostate cancer, age-related macular degeneration, breast cancer, cervical cancer, arterial disease

730nm

Aluminum phthalocyanine tetrasulfonate (AlPcS4)

Photosens

676 (200,000)

0.38

Russia (2001)—stomach, skin, lips, oral cavity, tongue, breast cancer

671nm

680nm

Silicon phthalocyanine (Pc4)

675 (200,000)

Clinical trials—actinic keratosis, Bowen’s disease, skin cancer, mycosis fungoides

671nm




Examples of non-porphyrin PDT candidates. None have received FDA approval for their application areas:

Compound

λmax(nm)

εmax (M−1cm−1)

Application

Laserglow Wavelengths Available

Hypericin

590

44,000

squamous cell carcinoma, basal cell carcinoma

589nm

Methylene blue

666

82,000

melanoma, basal cell carcinoma, Kaposi’s sarcoma, chronic periodontitis

665nm

Toluidine blue

630

51,000

chronic periodontitis

633nm

Rose bengal

549

100,000

breast carcinoma, melanoma

543nm

556nm

TH9402

514

100,000

graft-versus-host disease

515nm

Merocyanine 540

556

110,000

leukemia, lymphoma

556nm

Curcumin

420

55,000

oral disinfectant

415nm - 420nm



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Product Wavelength Description Starting At In Stock
633 nm633 nm Collimated Diode Laser System
5 - 80 mW Output Power
$2,143.00

Specs
635 nm

Best Seller!

635 nm Collimated Diode Laser System
5 - 500 mW Output Power
$1,063.00

Specs
635 nm

Best Seller!

635 nm Collimated Diode Laser System
1000 - 1000 mW Output Power
$4,734.00

Specs
635 nm

Best Seller!

635 nm Collimated Diode Laser System
3000 - 6000 mW Output Power
$10,083.00

Specs
655 nm655 nm Collimated Diode Laser System
5 - 1000 mW Output Power
$1,200.00

Specs
655 nm655 nm Collimated Diode Laser System
5000 - 5000 mW Output Power
$9,928.00

Specs
690 nm690 nm Collimated Diode Laser System
100 - 800 mW Output Power
$3,615.00

Specs
760 nm760 nm Low-Noise Collimated Diode Laser System
5 - 5000 mW Output Power
$4,693.00

Specs

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