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PSY-NANO-SI — Result In Brief

Project ID: 13875
Funded under: FP6-NMP
Country: Spain

Common elements with special properties for biomedicine

Silicon and oxygen are essential to human life. Their interaction provides the potential for contributing to advances in important issues of human well-being.
Common elements with special properties for biomedicine
The 'Nanosilicon-based photosynthesis for chemical and biomedical applications' (Psy-nano-si) project studied silicon and oxygen, two of Earth's most common elements. The EU-funded team sought to examine a new type of interaction between the elements and to address important issues in biology, chemistry, medicine and physics. The main focus was on fundamental discoveries made by consortium members related to the generation of singlet oxygen by nano-silicon (Si) and its biodegradability.

Researchers aimed to discover the possible applications of porous silicon particles containing luminescent Si nanocrystals (nano-Si particles) as efficient generators of singlet molecular oxygen (1O2). The project intended to develop biologically tolerable and environmentally friendly materials and prototype systems that could compete with existing photosensitisers (PSs) in photochemical, biological and medical applications.

Psy-nano-si researchers discovered that certain nano-Si particles can be produced in large quantities. The process for producing photoactive particles by direct stain-etching of crystalline Si powders as well as equipment developed during the project can be easily rescaled to industrial production requirements.

Although nano-Si particles contain toxic impurities after stain-etching and are thus not appropriate for direct bio-medical applications, a cleaning procedure was shown to be efficient in removing the toxic substances. This now made the purified particles acceptable for bio-medical applications.

The nano-Si surface was modified in a manner that made the surface hydrophilic and stable against erosion under certain circumstances. Experimental work resulted in modified nano-Si surfaces forming a specific protective layer allowing for effective interaction between excited Si nanocrystals and molecular oxygen. This serves as a basis for photosensitising activity.

In photodynamic therapy (PDT) of tumours, a PS is administered to patients followed by irradiation of the tumour mass with light of an appropriate wavelength. Although this comes with the risk of oxidative damage, indirect effects have been shown to actually contribute to tumour destruction. A number of PSs are already being used in clinical practice. Project members developed the first solid-state PDT photosensitiser. This is a powder of micrometre- and sub-micrometre–size particles of nano-Si that can produce singlet oxygen.

Up to the time of its completion, the Psy-nano-si project developed software and connection protocols via the Internet, offered anti-theft measures, and tested the central server and its online launch.

Overall, the project identified the conditions under which nano-Si exhibits in vitro photocytotoxic and in vivo PDT activities. At this time, these conditions are still far from meeting the criteria for PDT drugs approval.

Work performed enabled researchers to develop methods of scalable production of porous-Si–based nano-Si materials as a new kind of solid-state photosensitisers and drug delivery agents. The results of the project have paved the way for further investigation of nano-Si surface transformation and photosensitising abilities for use in practical applications.

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