Silk fibroin-based delivery systems containing pro-photosensitizing agents for topical photodynamic therapy of wounds

Author(s)

Iris Sperchi Camilo Brait

• Document type: Master's Dissertation
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Ciências Farmacêuticas de Ribeirão Preto (PCARP/BC)
• Defense date: 2019-06-03

Examining board members

Renata Fonseca Vianna Lopez

• Advisor: Renata Fonseca Vianna Lopez

Abstract

Chronic wound treatments require the use of dressings which are capable of mechanically protecting the wound, contributing to the healing process and avoiding any microbial contamination. Photodynamic therapy (PDT) is a kind of treatment involving application of photosensitizing agents and light. PDT has been investigated for wounds treatment due to its modulatory capacity of immune response and its antimicrobial effect. The objective of this work was to develop a film dressing able to modulate the release of substances PDT-responsives aiming the healing of wounds. For this purpose, silk-fibroin films functionalized with a nitric oxide donor (NO), S-nitrosoglutathione (GSNO), containing 5-aminolevulinic acid (5-ALA) incorporated were developed. 5-ALA is a pro-photosensitizer that induces a production of protoporphyrin IX in vivo and has been explored on topical PDT of wounds. GSNO is able of releasing NO under light stimulus and low concentrations of NO released can aid in cell proliferation. Finally, silk fibroin is a natural biopolymer used as basis for cell growth. Fibroin dispersion was prepared from Bombyx cocoons and functionalized with GSNO (Fibroin-GSNO). Fibroin-GSNO conjugate was characterized by spectroscopic techniques and used to formulate films containing 5-ALA. Films were characterized by spectroscopic techniques, thermal analysis, mechanical and hydration properties, release kinetics of 5-ALA and NO in the presence of irradiation at specific wavelengths, cytotoxicity and phototoxicity and expression of the dermal healing mediator TGF-β. Modifications in intensity and displacement of bands of Fibroin-GSNO infrared spectrum in relation to fibroin spectrum, in addition to the emergence of a new band in 2.09 ppm in Fibroin-GSNO nuclear magnetic resonance spectrum, characteristic of an ester bond, indicated the functionalization of fibroin with GSNO. Fibroin-GSNO films were homogeneous and transparent, with dense surface and absence of pores, mechanical resistance, low swelling capacity and permeable to water vapor, with a water vapor transmission rate of about 2400 g/m2. Irradiation of the films at 377 nm and 447 nm resulted in controlled release of NO, with irradiation at 377 nm inducing the release of almost 20-fold more NO than the irradiation in the visible region. The release of 5-ALA from the films was independent of the light stimulus and sustained for 72 h, with release rate of approximately 25 µg/cm2/h1/2. In vitro studies on fibroblast culture indicated that the films were neither cytotoxic nor phototoxic when irradiated at 470 nm and light dose of 3 J/cm2. The films containing 5-ALA were able to increase 3-fold the expression of TGF-β relative to the control without 5-ALA, both in the presence and absence of light. Therefore, Fibroin-GSNO films containing 5-ALA are a promising strategy for wound healing. (AU)

• FAPESP's process: 17/18241-5 - Silk fibroin-based delivery systems containing pro-photosensitizing agents for topical photodynamic therapy of wounds
• Grantee: Iris Sperchi Camilo Brait
• Support Opportunities: Scholarships in Brazil - Master