Photoperoxidation in isolated chloroplasts. I. Kinetics and stoichiometry of fatty acid peroxidation.

The therapeutic properties of light have been known for thousands of years, but it was only in the last century that photodynamic therapy (PDT) was developed. At present, PDT is being tested in the clinic for use in oncology--to treat cancers of the head and neck, brain, lung, pancreas, intraperitoneal cavity, breast, prostate and skin. How does PDT work, and how can it be used to treat cancer and other diseases?

Photodynamic therapy for cancer

s, and 360 patents, and edited 12 books. He has also received over 80 major awards including the Gairdner Foundation International Award, Lemelson-MIT prize, ACS’s Applied Polymer Science and Polymer Chemistry Awards, AICHE’s Professional Progress, Bioengineering, Walker and Stine Materials Science and Engineering Awards. In 1989, Dr. Langer was elected to the Institute of Medicine of the National Academy of Sciences, and in 1992 he was elected to both the National Academy of Engineering and the National Academy of Sciences. He is the only active member of all three National Academies. Kevin Shakesheff was born in Ashington, Northumberland, U.K., in 1969. He received his Bacheclor of Pharmacy degree from the University of Nottingham in 1991 and a Ph.D. from the same institution in 1995. In 1996 he became a NATO Postdoctoral Fellow at MIT, Department of Chemical Engineering. He is currently an EPSRC Advanced Fellow at the School of Pharmaceutical Sciences, The University of Nottingham. His research group investigates new methods of engineering polymer surfaces and the application of these engineered materials in drug delivery and tissue engineering. 3182 Chemical Reviews, 1999, Vol. 99, No. 11 Uhrich et al.

Polymeric Systems for Controlled Drug Release

Additive manufacturing (AM) alias 3D printing translates computer-aided design (CAD) virtual 3D models into physical objects. By digital slicing of CAD, 3D scan, or tomography data, AM builds objects layer by layer without the need for molds or machining. AM enables decentralized fabrication of customized objects on demand by exploiting digital information storage and retrieval via the Internet. The ongoing transition from rapid prototyping to rapid manufacturing prompts new challenges for mechanical engineers and materials scientists alike. Because polymers are by far the most utilized class of materials for AM, this Review focuses on polymer processing and the development of polymers and advanced polymer systems specifically for AM. AM techniques covered include vat photopolymerization (stereolithography), powder bed fusion (SLS), material and binder jetting (inkjet and aerosol 3D printing), sheet lamination (LOM), extrusion (FDM, 3D dispensing, 3D fiber deposition, and 3D plotting), and 3D bioprinting....

Polymers for 3D Printing and Customized Additive Manufacturing

The use of lasers, over the past few decades, has emerged to be highly promising for cancer therapy modalities, most commonly the photothermal therapy method, which employs light absorbing dyes for achieving the photothermal damage of tumors, and the photodynamic therapy, which employs chemical photosensitizers that generate singlet oxygen that is capable of tumor destruction. However, recent advances in the field of nanoscience have seen the emergence of noble metal nanostructures with unique photophysical properties, well suited for applications in cancer phototherapy. Noble metal nanoparticles, on account of the phenomenon of surface plasmon resonance, possess strongly enhanced visible and near-infrared light absorption, several orders of magnitude more intense compared to conventional laser phototherapy agents. The use of plasmonic nanoparticles as highly enhanced photoabsorbing agents has thus introduced a much more selective and efficient cancer therapy strategy, viz. plasmonic photothermal therapy (PPTT). The synthetic tunability of the optothermal properties and the bio-targeting abilities of the plasmonic gold nanostructures make the PPTT method furthermore promising. In this review, we discuss the development of the PPTT method with special emphasis on the recent in vitro and in vivo success using gold nanospheres coupled with visible lasers and gold nanorods and silica-gold nanoshells coupled with near-infrared lasers.

http://wiki.phy.queensu.ca/shughes/images/0/0f/Cancer_3.pdf

Plasmonic photothermal therapy (PPTT) using gold nanoparticles

Several photosensitizing porphyrins are selectively retained in solid tumors and other rapidly growing tissues in humans and other mammals. On subsequent illumination with light of wavelengths absorbed by the porphyrin, tumors can be destroyed with relatively little damage to the surrounding normal tissue; it is generally assumed that tumor damage is mediated by singlet oxygen generated by the light excited sensitizer. In clinical practice the patient is injected intravenously with a few mg/kg of the porphyrin. Then, 48-72 h later (an interval necessary to attain the maximum differential concentration of porphyrin in the tumor) the tumor area is illuminated with an appropriate dose of light (25-50 J/cm); typically a dye laser tuned to an absorption peak of the porphyrin is used. The only side effect observed in patients is a skin photosensitivity that persists for a month or so. This photochemotherapeutic procedure, termed photodynamic therapy (PDT)*, has been used on several thousand patients, with generally encouraging results (Dougherty ,1984, 1985). In spite of the utility of the technique, PDT as presently used suffers from some disadvantages. The photosensitizer preparation most generally used is a complex mixture of porphyrins termed hematoporphyrin derivative (HPD). This is prepared by subjecting hematoporphyrin acetates to alkaline hydrolysis. The composition of the mixture varies in different preparations and with time of storage. The most active component has been described as a dihematoporphyrin ether (Dougherty, 1985) or ester (Kessel, 1985); however these are not available as pure chemicals. Red light, usually from a dye laser tuned to 630 nm (corresponding to the longest wavelength absorption peak of HPD), is most commonly used in PDT to permit the maximum depth of

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1751-1097.1986.tb05648.x

Phthalocyanines as photosensitizers in biological systems and for the photodynamic therapy of tumors.

The load-strain and stress-relaxation behavior of wet rat tail tendon has been examined with respect to the parameters strain, rate of straining, and temperature. It is found that this mechanical behavior is reproducible after resting the tendon for a few minutes after each extension so long as the strain does not exceed about 4 per cent. If this strain is exceeded, the tendon becomes progressively easier to extend but its length still returns to the original value after each extension. Extensions of over 35 per cent can be reached in this way. Temperature has no effect upon the mechanical behavior over the range 0–37°C. Just above this temperature, important changes take place in the mechanical properties of the tendon which may have biological significance. The application of the techniques used here to studies of connective tissue disorders is suggested. Some of the mechanical properties of tendon have been interpreted with a simple model.

https://rupress.org/jgp/article-pdf/43/2/265/1242194/265.pdf

The Mechanical Properties of Rat Tail Tendon.

Cationic porphyrins have been shown to photoinduce the direct inactivation of Gram-positive (G+) and Gram-negative (G−) bacteria, thereby differing from anionic or neutral porphyrins which can photosensitize the G− bacteria only after permeabilization of their outer membrane. The present data show that the differences between these positively and negatively charged porphyrins are not related by a difference in the intrinsic photosensitizing efficiency, as determined by the photo-oxidation of model substrates or the yield of 1O2 generation; moreover, there are only minor differences in the quantum yield of porphyrin photobleaching. Rather, it appears that the positive charge promotes an electrostatic binding of the porphyrin to the outer cell surface inducing an initial limited damage which favours the penetration of the photosensitizer. Actually, the overall photoprocess is inhibited by the preincorporation of the porphyrin into liposomes, while it is enhanced by using amphiphilic dicationic porphyrins which bind to endocellular sites in larger amounts and in a more stable form.

Studies on the mechanism of bacteria photosensitization by meso-substituted cationic porphyrins

The photodynamic therapy (PDT) of tumors involves illumination of the tumorous area following the administration of a tumor-localizing photodynamic sensitizer. Hematoporphyrin derivative (HPD) and Photofrin II (a purified form of HPD), the main sensitizers used clinically for PDT to date, are complex mixtures of porphyrins; furthermore, these preparations absorb light very poorly in the red region of the spectrum (wavelengths greater than 600 nm) where light penetration into mammalian tissues is greatest. Thus there is considerable interest in identifying new sensitizers that localize more effectively in tumors, absorb more strongly at longer wavelengths and can be prepared in high purity. Much of this interest has been directed towards chlorins (reduced porphyrins), which typically absorb strongly in the red. This review summarizes research that has been carried out on selected types of chlorins, some of which may have important applications as sensitizers for PDT.

John D. Spikes

Papers

Phthalocyanines as photosensitizers in biological systems and for the photodynamic therapy of tumors.

The Mechanical Properties of Rat Tail Tendon.

Studies on the mechanism of bacteria photosensitization by meso-substituted cationic porphyrins

Chlorins as photosensitizers in biology and medicine.

Phthalocyanines: Properties and Applications