the photolinkers consists of two functional groups that serve to establish the bond with the active ingredient and the bond with the waveguide surface . a possible immobilization strategy is the modification of the surface , i . e . by a wet - chemical process or by plasma treatment , to produce functional groups thereon . for instance ( primary ) amino or hydroxy groups are suited for this . if the linker molecule is provided with an ( active ) ester ( e . g . n - hydrosuccinimide ester ) or if it is activated for example with edc , it can react with the amino or hydroxy groups on the waveguide surface to form carboxylic acid amide and ester , respectively . hence , the linker molecule is covalently anchored to the surface . likewise , the active ingredient molecule must be provided with the linker . to this end similar chemical reactions can here be carried out as on the waveguide surface . ring formation on the surface and polymerization , respectively , must be prevented through a protective group strategy , if necessary . apart from the two functional groups for reaction with the active ingredient molecule and with the surface , the molecule must have a photolabile bond to release the active ingredient . in the reaction between active ingredient molecule and photolinker , attention must be paid that upon release a possible residue of the photolinker on the active ingredient molecule shows no disadvantageous behavior in its effect ( effect and side - effect ). the structure of the photolabile linker 3 is only shown by way of example in fig1 , where the immobilization of the photolabile linker 3 on the polymer surface is symbolically illustrated with a wavy line 5 . likewise , the active ingredient ( medicament ) 4 is just outlined symbolically via a hexagon ; a specific structure of the active ingredient shall not be predetermined thereby . the photolabile linker 3 can be cleaved by light pulses l in the waveguide 2 . this process is outlined in the circle designated by x for an exemplary wavelength in the uv light range of λ = 365 nm through the further wave line . hence , the transdermal therapeutic system releases the active ingredient 4 upon cleavage of the photolabile linker 3 . the light pulse l is generated by means of the light source 6 and coupled via an optical device into the optical waveguide 2 . the light source 6 is controlled via the electronic system 7 . however , it is also possible in a further embodiment to form the optical waveguide at least sectionwise as a photonic crystal , the light source being then integratable into the region of the photonic crystal . the photonic crystal enables a filtering of the broad - band radiation , which is e . g . emitted by thermal radiation . a separate optical system for coupling in the radiation is not required in this embodiment . likewise , it is also possible to provide an electrically conductive and / or magnetic metal in a portion of the photonic crystal , the metal being heatable by the action of an electric and / or magnetic field . it is thereby possible to integrally form the light source in the waveguide . moreover , the coupling of light into the waveguide can then be omitted altogether . light waves l coupled into the waveguide 2 ( or generated therein as has been explained above ) produce an evanescent field in the environment of the optical waveguide 2 . the photolabile linker 3 is cleaved by the action of the evanescent field produced by light pulses in the optical waveguide , thereby releasing the active ingredient , which offers a considerable advantage over a merely continuous release . there are photolabile linkers ( also called photosensitive linkers ) for a wide wavelength range , both in the visible light and in the uv - light range . a possible light source 6 for the use of the transdermal therapeutic system would therefore be offered by commercially available uv - leds , e . g . in the range of λ = 365 nm , as outlined in fig1 . in this wavelength range there exist suitable photolabile linkers , of which two are shown in fig2 a and 2b by way of example . a list of various photosensitive linkers that can be used in the present invention is given in bannwarth , w ., hinzen , b ., combinatorial chemistry , vol . 25 , wiley - vch . the transdermal therapeutic system as described herein is thus based on the cleavage of the photolabile linkers in the evanescent field of the optical waveguide , which enables the use of uv light without damage to the patient &# 39 ; s skin because the light power in the evanescent filed can be kept low . moreover , when uv light is used , the photolabile linker need not be shielded against daylight . since wound bandages or also patches are normally exposed to visible light at least temporarily , such a shield would be required if wavelength ranges of the visible light were used . consequently , the use of uv light permits an unproblematic application of the transdermal therapeutic system also in daylight . at the same time the use of uv light prevents the propagation of germs , or the like , on the polymer surface owing to the antimicrobial action thereof , whereby the risk of allergies or infections is additionally reduced . in contrast to the above - described electrochemically - based controllable transdermal therapeutic system , also uncharged molecules can be used in the transdermal therapeutic system described herein with optically controlled active - ingredient dosage , whereby the range of application of this transdermal therapeutic system is increased considerably . since with a direct immobilization of the active ingredient via neutral photolabile linkers an adhesive layer between carrier material and active ingredient can be dispensed with , the risk of a contact allergy in the patient is minimized . an optically based control system additionally offers the possibility of determining the real dose of released active ingredient through corresponding sensors and of directly intervening in the further therapy , if necessary , after the data have been transmitted to the attending physician . one possibility of detecting the effectively released active - ingredient dose by integration of corresponding sensors is the measurement of the extinction of the light in the optical waveguide in response to the surface covering density by means of a diode array . possible fields of application of the present transdermal therapeutic system are the therapy of chronic wounds or chemotherapy . a comparison of the time curve of the active ingredient release in the case of different forms of administration is shown in fig3 . in fig3 , the corresponding dose of active ingredient is plotted over time . here curve a ( continuous line ) shows the active ingredient distribution for an administration by way of injection or a tablet . the rapid rise in the amount of active ingredient and the subsequent , also rapid , drop in the dose of active ingredient is clearly visible . curve b ( broken line ) shows the distribution of the active ingredient dose over time for a passive transdermal therapeutic system , wherein the rapid rise in combination with the time - constant active - ingredient release becomes apparent . curves c , d and e ( dash - dotted lines ) show individual active - ingredient dose deliveries with the present transdermal therapeutic system . the adaptivity of the amount of the active - ingredient dose delivery over time becomes thereby apparent . in the present embodiments an immobilization of photolabile linkers is possible over a wide wavelength spectrum , and a special advantage of the use of a uv light source is here the unproblematic application of the transdermal therapeutic system in daylight . furthermore , an exploitation of the antimicrobial action of the uv light is also possible . apart from a polymer fiber or a network / mesh of polymer fibers , a planar carrier film into which light is coupled in a corresponding way is also possible as a “ substrate ” for the photolabile linker . apart from this , organic semiconductive polymers can also be used . these are employed for making oleds ( organic light - emitting diodes ). a structure consisting of a plurality of organic layers is here in particular possible . a composite of polymer fibers is advantageous insofar as the enlarged surface entails a higher active - ingredient capacity . two possible photolabile linkers are shown in fig2 a and 2b . in principle , however , a great number of possible photolabile linkers are available , also for wavelengths other than the one specified in the instant case .
the present invention relates to a transdermal therapeutic system for the controllable release of an active ingredient , particularly a substance promoting wound healing , to a chronic wound or for chemotherapy , with at least one waveguide , wherein the active ingredient is deposited on the waveguide via a bond that is cleavable by electromagnetic pulses in the waveguide .