Beta-Functionalized Chlorin Photosensitizers for Deep Tissue PDT
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Solution Overview
Problem
Current photosensitizers for photodynamic therapy (PDT) have limited absorption in the red and near-infrared region, making it difficult to effectively target deep tissues, and existing methods for synthesizing chlorins are either resource-intensive or inefficient.
Innovation Solution
Development of β-functionalized hydroxy- and dihydroxy-chlorin structures with enhanced absorption in the red and near-infrared region, synthesized through methods involving nucleophilic or organometallic agents, and formulated into liposomal preparations to improve membrane affinity and PDT efficacy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If current photosensitizers are used for PDT, then the treatment can be performed, but the absorption in the red and near-infrared region is limited, making it difficult to target deep tissues
Solution Approach 1:
The patent modifies the molecular structure of chlorin photosensitizers by introducing β-functional groups (such as carboxylic acid, amide, and ester groups at positions 7 and 8 of the chlorin ring). This structural parameter change extends the absorption spectrum into the red and near-infrared region (650-900 nm), enabling deeper tissue penetration while maintaining photosensitizing activity
Solution Approach 2:
The patent creates composite structures by combining chlorin core molecules with various β-substituent groups. These composite photosensitizers integrate the light-absorbing properties of chlorin with the functional properties of different substituents, achieving both deep tissue penetration and enhanced biological activity
2Ease of manufacture
If chlorins are derived from natural compounds like chlorophylls, then the synthesis can be performed, but the process requires vast resources and is difficult due to sensibility of natural compounds
Solution Approach 1:
The patent segments the synthesis process into two independent stages: first synthesizing the porphyrin precursor through controlled condensation reactions, then converting it to the chlorin derivative through reduction. This segmentation avoids the need to handle sensitive natural chlorophylls throughout the entire process, reducing resource requirements and simplifying manufacturing
Solution Approach 2:
The patent employs readily available and inexpensive chemical reagents for porphyrin synthesis (such as pyrrole, aldehydes, and acid catalysts) rather than relying on scarce natural chlorophyll sources. This substitution with cheap synthetic precursors dramatically reduces the quantity of resources required while maintaining product quality
3Manufacturing precision
If porphyrin is converted to chlorin by reduction with in situ generated di-imine or cis-dihydroxylation with osmium tetroxide, then the chlorin system is formed, but the methods are complex and require multiple steps
Solution Approach 1:
The patent extracts and isolates the key transformation step from the complex multi-step sequences. By using pre-formed diimine reagents or simplified dihydroxylation conditions, the method removes unnecessary intermediate steps and reagent preparations, achieving direct conversion from porphyrin to chlorin with improved precision and reduced complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The β-functionalized chlorins demonstrate increased absorption in the red and near-infrared region, enabling deeper tissue penetration and enhanced selectivity for target tissues, while the liposomal formulation prevents undesirable effects like precipitation and delayed pharmacokinetics, thereby improving PDT efficacy.
Implementation Method 1
a desirable characteristic in order to efficiently destroy deep target tissues is a strong absorption at long wavelength. Chlorins have the advantage that they possess an intense absorption in the red and near-infrared region of the electromagnetic spectrum
Implementation Method 2
the liposomal formulation prevents undesirable effects like precipitation and delayed pharmacokinetics
Data Source
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AI summary
The present invention provides methods to obtain biologically active compounds that can be used as photosensitizers for diagnostic and therapeutic applications, particularly for PDT of cancer, infections and other hyperproliferative diseases, fluorescence diagnosis and PDT treatment of a non-tumorous indication such as arthritis, inflammatory diseases, viral or bacterial infections, dermatological, ophthalmological or urological disorders. An embodiment of the present invention consists of a method to synthesize diketo-chlorins as precursors. In yet another embodiment these precursors are converted to ß-unctionalized hydroxy- and dihydroxy-chlorins. Another embodiment is to provide amphiphilic compounds with a higher membrane affinity and increased PDT-efficacy. Another embodiment consists of the formulation of the desired isomer into a liposomal formulation to be injected avoiding undesirable effects like precipitation at the injection site or delayed pharmacokinetics of the tetrapyrrole systems.