4. DiscussionDrug delivery at targe

4. Discussion

Drug delivery at targeted sites and its further controlled release is dramatically helping in the treatment of many diseases. The layer-by-layer fabrication technique offers a straight forward mechanism for drug delivery applications as their highly tunable properties may lead to controllable drug release behavior (Peyratout and Dahne, 2004; Hammond, 2004). Within this system it is also possible to deploy biodegradable polymer for drug delivery at predetermined rates, and device degradation afterwards. เท our study we fabricated a multilayered structure by blending selfdegrading polymer with silk fibroin protein. Several biodegradable polymers are popularly used for this purpose, such as poly (glycol-ide), poly(lactide-co-glycolide), poly (3-hydroxybutyrate), gelatin, chitosan, alginate and so on (Soppimath et al., 200ใ ะ Panyam and Labhasetwar, 2003). We employed gelatin as it is highly biocompatible and is widely used in therapeutics (Chakfe et al., 1993; Ulubayram et al., 2001 ะ Drave et al., 1998; Sung et al., 1999).

Multilayered fibroin/gelatin films of different ratios were successfully fabricated by treating each layer with methanol. Methanol treatment induced transition from random coil to P-sheets, which provided physical crosslink between fibroin/gelatin giving rise to the structural stability to the layers also shown by previous groups (Gil et al., 2005,2007). Build up of layers was monitored by UV-vis spectra which showed that absorbance at particular wavelength characteristic of the silk fibroin increased with increase in number of layers (Fig. 3). Methanol treatment also made the surface hydrophobic, which was shown by contact angle studies done by Hofmann et al. (2006). Hence it can be concluded that stacking of

blend layers was possible ue to hydrophobic interactions among the layers and build up of

^M^rs was ^ident ky ATR-FTIR(Fig. 3). SEM images provide further evidence of layer formation but it was observed that in multilayer system having high gelatin content layers were obscure (Fig. 6). Distinct layers could only be seen in fibroin/gelatin ratio 4:1.

On comparison of mechanical strength of multilayer films with single layer film, it was observed that tensile strength and young modulus increased almost twofolds. Mechanical properties also varied with concentration of gelatin. The results indicated that inducing multilayer and blending gelatin at low concentration were effective in improving the mechanical properties. Mechanical properties, particularly tensile strength and elongation at break are important for evaluating the performance of multilayered films for both in vitro and in vivo applications.

Present study was primarily focused in exploring silk fibroin/gelatin multilayer system for drug delivery application. Silk fibroin is used in various delivery applications exploiting its various potentials such as control of crystallinity to deliver nerve growth factor and at the same time maintaining NGF bioactivity even after methanol treatment (Uebersax et al.t 2007). In silk fibroin/gelatin blend multilayer films, the aspect of fibroin insolubility induced by methanol treatment was employed, resulting in partial degradation of the system due to dissolution of self-degradable gelatin. Thus silk fibroin provided a rigid platform for controlled release over period of several days.

Release behavior from fibroin/gelatin multilayer film was studied by incorporating model compounds that varied in their molecular weights. This gave an idea so as to how compounds similar in molecular weights will behave using this system for delivery applications. Trypan blue a hydrophilic, low molecular weight (961 Da) compound was used as it can be traced spectrophotomet-rically (Qian et al., 2001). Among high molecular weight molecules FITC-inulin and FITC-BSAwith molecular weights of 3.9 and 66kDa were used. It was observed that release was not governed by the size of the molecules, as their release profiles for similar composition of fibroin/gelatin multilayer were comparable Release was dependent on the degradation profile of the system except for the first 2-3 days where release was dominated by diffusion and var-led due to molecular weight of molecules (Fig. 8a. c and e). But later on the release profile was compliant with degradation profile Consequently, it was observed that acceleration in polymer degradation lead to increased mobility of the model compound

within the polymeric matrix, resulting in increased absolute and relative release rates (Fig. 7). It was observed when gelatin content was decreased in the system, initial burst was suppressed and release duration was also prolonged. Addition of extra layer had also similar effect- Moreover, it also improved the release profile of multilayer with high gelatin content by providing extra barrier layer to assuage initial burst (Fig. 8b. d and 0- It can be concluded that in fibroin/gelatin multilayer films release was reliant on the shielding effect of the layers and the gelatin content. Mathematical model was done using Ritger-Peppas equation (Ritger and Peppas, ใ987a.b) on the obtained experimental data sets further suggested that the release behavior to be a combined mechanism of fick’s diffusion and polymer erosion/degradation (Table 1). Fick's second law of diffusion further elaborated the results obtained by validating the fact of polymer degradation to be the major contributor in five-layered films for modd compound release (Fig. 10).The present study provides significant insight into formulation variables, which can be adjusted to achieve a variety of release rates and lower initial bursts.

Moreover, cell viability as analyzed using MTT and confocal microscopy had provided an evidence for excellent biocompatibility of fibroin/gelatin blend films (Fig. n A and B) (Fan et al., 2008). We can envisage silk fibroin/gelatin multilayer system for delivering various bioactive molecules such as therapeutics and growth factors. As silk fibroin acts as suitable substrate for fibroblast cells, if fibroblast growth factors are incorporated within the multilayer structure, its cytocompatibility will be further enhanced. As this system undergoes partial degradation, therefore, it eventually may be utilized for development of whole skin substitutes.

ผลลัพธ์ (อังกฤษ) 1:

4. DiscussionTargeted Drug delivery and controlled sites at its further release of the treatment is helping dramatically in many diseases. The fabrication technique offers straight forward a layer-by-layer mechanism for drug delivery applications as their highly tunable properties may lead to controllable drug release behavior (Peyratout Dahne; 2004, and Hammond, 2004). it is also possible Within this system to deploy for biodegradable polymer drug delivery at predetermined rates, and device degradation afterwards we study our heritage. a multilayered structure fabricated by blending with silk fibroin selfdegrading protein polymer Several biodegradable polymers are used popularly. for this purpose, such as poly (glycol-ide), poly (lactide-co-glycolide), poly (3-hydroxybutyrate), gelatin, alginate, chitosan and so on (Soppimath et al., 2003, is to get 200 and Panyam Labhasetwar). We employed it as gelatin is highly biocompatible and is widely used in therapeutics (Chakfe et al., 1993; Ulubayram et al., 2001 et al. 1998, Drave ะ; Sung et al., 1999).Multilayered fibroin/gelatin films of different ratios were successfully fabricated by treating each layer with methanol. Methanol treatment induced transition from random coil to P-sheets, which provided physical crosslink between fibroin/gelatin giving rise to the structural stability to the layers also shown by previous groups (Gil et al., 2005,2007). Build up of layers was monitored by UV-vis spectra which showed that absorbance at particular wavelength characteristic of the silk fibroin increased with increase in number of layers (Fig. 3). Methanol treatment also made the surface hydrophobic, which was shown by contact angle studies done by Hofmann et al. (2006). Hence it can be concluded that stacking ofblend layers was possible ue to hydrophobic interactions among the layers and build up of^M^rs was ^ident ky ATR-FTIR(Fig. 3). SEM images provide further evidence of layer formation but it was observed that in multilayer system having high gelatin content layers were obscure (Fig. 6). Distinct layers could only be seen in fibroin/gelatin ratio 4:1.On comparison of mechanical strength of multilayer films with single layer film, it was observed that tensile strength and young modulus increased almost twofolds. Mechanical properties also varied with concentration of gelatin. The results indicated that inducing multilayer and blending gelatin at low concentration were effective in improving the mechanical properties. Mechanical properties, particularly tensile strength and elongation at break are important for evaluating the performance of multilayered films for both in vitro and in vivo applications.Present study was primarily focused in exploring silk fibroin/gelatin multilayer system for drug delivery application. Silk fibroin is used in various delivery applications exploiting its various potentials such as control of crystallinity to deliver nerve growth factor and at the same time maintaining NGF bioactivity even after methanol treatment (Uebersax et al.t 2007). In silk fibroin/gelatin blend multilayer films, the aspect of fibroin insolubility induced by methanol treatment was employed, resulting in partial degradation of the system due to dissolution of self-degradable gelatin. Thus silk fibroin provided a rigid platform for controlled release over period of several days.Release behavior from fibroin/gelatin multilayer film was studied by incorporating model compounds that varied in their molecular weights. This gave an idea so as to how compounds similar in molecular weights will behave using this system for delivery applications. Trypan blue a hydrophilic, low molecular weight (961 Da) compound was used as it can be traced spectrophotomet-rically (Qian et al., 2001). Among high molecular weight molecules FITC-inulin and FITC-BSAwith molecular weights of 3.9 and 66kDa were used. It was observed that release was not governed by the size of the molecules, as their release profiles for similar composition of fibroin/gelatin multilayer were comparable Release was dependent on the degradation profile of the system except for the first 2-3 days where release was dominated by diffusion and var-led due to molecular weight of molecules (Fig. 8a. c and e). But later on the release profile was compliant with degradation profile Consequently, it was observed that acceleration in polymer degradation lead to increased mobility of the model compoundWithin the polymeric matrix, resulting in increased absolute and relative release rates (Fig. 7). It was observed when the content was decreased in gelatin system, initial burst release was suppressed and was also prolonged duration of layer also had extra Addition. a similar effect-Moreover, it also improved the release profile of multilayer with high gelatin content by providing extra barrier layer to assuage initial burst (Fig. 8b. 0 and d-It can be concluded that gelatin films in multilayer fibroin/release was reliant on the shielding effect of the layers and the gelatin content. Mathematical model was done using Ritger-Peppas equation (and get a 987 Peppas, Ritger. b) on the experimental data obtained suggested that further sets the behavior to be a release mechanism of combined. fick's diffusion and polymer erosion/degradation (Table 1). Fick's second law of diffusion further elaborated the results obtained by validating the fact of polymer degradation to be the major contributor in five-layered films for modd compound release (Fig. 10).The present study provides significant insight into formulation variables, which can be adjusted to achieve a variety of release rates and lower initial bursts.Moreover, cell viability as analyzed using MTT and confocal microscopy had provided an evidence for excellent biocompatibility of fibroin/gelatin blend films (Fig. n A and B) (Fan et al., 2008). We can envisage silk fibroin/gelatin multilayer system for delivering various bioactive molecules such as therapeutics and growth factors. As silk fibroin acts as suitable substrate for fibroblast cells, if fibroblast growth factors are incorporated within the multilayer structure, its cytocompatibility will be further enhanced. As this system undergoes partial degradation, therefore, it eventually may be utilized for development of whole skin substitutes.

ผลลัพธ์ (อังกฤษ) 2:

4. Discussion Drug Delivery at targeted sites and ITS further controlled release is dramatically helping in the Treatment of many diseases. The layer-by-layer Fabrication Technique offers a Straight Forward Mechanism for Drug Delivery Applications As their highly tunable properties May Lead to Drug controllable. release behavior (Peyratout and Dahne, 2004; Hammond, 2004). Within this system it is also possible to deploy biodegradable polymer for drug delivery at predetermined rates, and device degradation afterwards. Pour our study we fabricated a multilayered structure by blending selfdegrading polymer with. silk fibroin protein. Several biodegradable polymers are popularly used for this purpose, such as poly (glycol-ide), poly (lactide-co-glycolide), poly (3-hydroxybutyrate), gelatin, chitosan, alginate and so on (Soppimath et. al., 200 g each Panyam and Labhasetwar, 2003). We employed gelatin as it is highly biocompatible and is widely used in therapeutics (Chakfe et al., 1993; Ulubayram et al., 2001 will Drave et al., 1998; Sung. et Al., 1 999). multilayered fibroin / Gelatin Films of different ratios were successfully fabricated by treating each layer with methanol. Methanol Treatment induced transition from Random Coil to P-sheets, which provided physical crosslink between fibroin / Gelatin giving rise to the structural. stability to the layers also shown by previous groups (Gil et al., 2005,2007). Build up of layers was monitored by UV-vis spectra which showed that absorbance at particular wavelength characteristic of the silk fibroin increased with increase in number of layers. (Fig. 3). Methanol Treatment also Made the surface hydrophobic, which was shown by Contact Angle Studies done by Hofmann et Al. (the 2,006th). Hence it Can be concluded that Stacking of Blend layers was possible UE to hydrophobic interactions among the layers. and Build up of ^ M ^ ^ ident KY ATR-FTIR was RS (Fig. 3). SEM images provide further layer Evidence of Formation but it was observed that in multilayer System High Gelatin Having content were obscure layers (Fig. 6). Distinct layers could only be seen in fibroin / Gelatin ratio 4: 1. On comparison of Mechanical strength of multilayer Film Films with single layer, it was observed that tensile strength and Young modulus Increased Almost Twofolds. Mechanical properties also varied with concentration of Gelatin. the results Indicated that inducing multilayer and blending Gelatin at low concentration were effective in Improving the Mechanical properties. Mechanical properties, particularly tensile strength and elongation at break are important for evaluating the Performance of multilayered Films for both in vitro and in vivo Applications. Present Study. was primarily focused in exploring silk fibroin / gelatin multilayer system for drug delivery application. Silk fibroin is used in various delivery applications exploiting its various potentials such as control of crystallinity to deliver nerve growth factor and at the same time maintaining NGF bioactivity even after methanol treatment. (Uebersax et al.t 2007). In silk fibroin / gelatin blend multilayer films, the aspect of fibroin insolubility induced by methanol treatment was employed, resulting in partial degradation of the system due to dissolution of self-degradable gelatin. Thus silk fibroin provided. a rigid Platform for controlled release over period of several days. Release behavior from fibroin / Gelatin multilayer Film was studied by incorporating Model compounds that varied in their molecular Weights. This Gave an Idea so As to How compounds Similar in molecular Weights Will behave using this. system for delivery applications. Trypan blue a hydrophilic, low molecular weight (961 Da) compound was used as it can be traced spectrophotomet-rically (Qian et al., 2001). Among high molecular weight molecules FITC-inulin and FITC-BSAwith molecular. weights of 3.9 and 66kDa were used. It was observed that release was not governed by the size of the molecules, as their release profiles for similar composition of fibroin / gelatin multilayer were comparable Release was dependent on the degradation profile of the system except for the. first 2-3 days where release was dominated by diffusion and var-led due to molecular weight of molecules (Fig. 8a. c and e). But later on the release profile was compliant with degradation profile Consequently, it was observed that acceleration in. polymer degradation Lead to Increased Mobility of the Model Compound Within the polymeric Matrix, resulting in Increased Absolute and Relative release Rates (Fig. 7). It was observed when Gelatin content was Decreased in the System, initial Burst was suppressed and release Duration was also. prolonged. Addition of extra layer had also similar effect- Moreover, it also improved the release profile of multilayer with high gelatin content by providing extra barrier layer to assuage initial burst (Fig. 8b. d and 0- It can be concluded that in fibroin. / gelatin multilayer films release was reliant on the shielding effect of the layers and the gelatin content. Mathematical model was done using Ritger-Peppas equation (Ritger and Peppas, t 987a.b) on the obtained experimental data sets further suggested that the release behavior. to be a combined mechanism of fick's diffusion and polymer erosion / degradation (Table 1). Fick's second law of diffusion further elaborated the results obtained by validating the fact of polymer degradation to be the major contributor in five-layered films for modd compound release (. fig. 10) .The present Study provides significant Insight into formulation variables, which Can be adjusted to Achieve a Variety of release Rates and Lower initial bursts. Moreover, Cell viability and confocal microscopy As analyzed using MTT had provided for an Excellent biocompatibility of Evidence. fibroin / gelatin blend films (Fig. n A and B) (Fan et al., 2008). We can envisage silk fibroin / gelatin multilayer system for delivering various bioactive molecules such as therapeutics and growth factors. As silk fibroin acts as suitable substrate. for fibroblast cells, if fibroblast growth factors are incorporated within the multilayer structure, its cytocompatibility will be further enhanced. As this system undergoes partial degradation, therefore, it eventually may be utilized for development of whole skin substitutes.

ผลลัพธ์ (อังกฤษ) 3:

4. Discussion

Drug delivery at targeted sites and its further controlled release is dramatically helping in the treatment. Of many diseases. The layer-by-layer fabrication technique offers a straight forward mechanism for drug delivery applications. As their highly tunable properties may lead to controllable drug release behavior (Peyratout and Dahne 2004;,, Hammond 2004).Within this system it is also possible to deploy biodegradable polymer for drug delivery at predetermined rates and device,, Degradation afterwards. Pour our study we fabricated a multilayered structure by blending selfdegrading polymer with silk. Fibroin protein. Several biodegradable polymers are popularly used for this purpose such as, poly (glycol-ide), poly (lactide-co-glycolide),Poly (3-hydroxybutyrate), gelatin chitosan, alginate and, so on (Soppimath et al, 200 m, Panyam, and Labhasetwar 2003).? We employed gelatin as it is highly biocompatible and is widely used in therapeutics (Chakfe et al, 1993; Ulubayram et. Al, 2001. Drave et al, 1998; Sung et al, 1999).

.Multilayered fibroin / gelatin films of different ratios were successfully fabricated by treating each layer with, methanol. Methanol treatment induced transition from random coil to P-sheets which provided, physical crosslink between fibroin / gelatin. Giving rise to the structural stability to the layers also shown by previous groups (Gil et al, 2005 2007,).Build up of layers was monitored by UV-vis spectra which showed that absorbance at particular wavelength characteristic. Of the silk fibroin increased with increase in number of layers (Fig. 3). Methanol treatment also made the, surface hydrophobic. Which was shown by contact angle studies done by Hofmann et al. (2006). Hence it can be concluded that stacking of

.Blend layers was possible ue to hydrophobic interactions among the layers and build up of




M RS was ident KY ATR-FTIR (Fig.? 3). SEM images provide further evidence of layer formation but it was observed that in multilayer system having high gelatin. Content layers were obscure (Fig. 6). Distinct layers could only be seen in fibroin / gelatin ratio 4: 1.

.On comparison of mechanical strength of multilayer films with single, layer film it was observed that tensile strength. And young modulus increased almost twofolds. Mechanical properties also varied with concentration of gelatin. The results. Indicated that inducing multilayer and blending gelatin at low concentration were effective in improving the mechanical. Properties, Mechanical properties.Particularly tensile strength and elongation at break are important for evaluating the performance of multilayered films. For both in vitro and in vivo applications.

Present study was primarily focused in exploring silk fibroin / gelatin multilayer. System for drug delivery application.Silk fibroin is used in various delivery applications exploiting its various potentials such as control of crystallinity. To deliver nerve growth factor and at the same time maintaining NGF bioactivity even after methanol treatment (Uebersax. Et al.t 2007). In silk fibroin / Gelatin Blend multilayer films the aspect, of fibroin insolubility induced by methanol treatment. Was, employedResulting in partial degradation of the system due to dissolution of self-degradable gelatin. Thus silk fibroin provided. A rigid platform for controlled release over period of several days.

Release behavior from fibroin / gelatin multilayer film. Was studied by incorporating model compounds that varied in their molecular weights.This gave an idea so as to how compounds similar in molecular weights will behave using this system for delivery, applications. Trypan blue, a hydrophilic low molecular weight (961 Da) compound was used as it can be traced spectrophotomet-rically (Qian. Et al, 2001). Among high molecular weight molecules FITC-inulin and FITC-BSAwith molecular weights of 3.9 and 66kDa were. Used.It was observed that release was not governed by the size of the molecules as their, release profiles for similar composition. Of fibroin / gelatin multilayer were comparable Release was dependent on the degradation profile of the system except for. The first 2-3 days where release was dominated by diffusion and var-led due to molecular weight of molecules (Fig. 8A. C. And E).But later on the release profile was compliant with degradation, profile Consequently it was observed that acceleration. In polymer degradation lead to increased mobility of the model compound

within the polymeric matrix resulting in, increased. Absolute and relative release rates (Fig. 7). It was observed when gelatin content was decreased in, the systemInitial burst was suppressed and release duration was also prolonged. Addition of extra layer had also similar effect -. Moreover it also, improved the release profile of multilayer with high gelatin content by providing extra barrier layer. To assuage initial burst (Fig. 8b.D and 0 - It can be concluded that in fibroin / gelatin multilayer films release was reliant on the shielding effect of the. Layers and the gelatin content. Mathematical model was done using Ritger-Peppas equation (Ritger and Peppas, 987a.B) on the obtained experimental data sets further suggested that the release behavior to be a combined mechanism of Fick s. ' Diffusion and polymer erosion / degradation (Table 1). Fick 's second law of diffusion further elaborated the results obtained. By validating the fact of polymer degradation to be the major contributor in five-layered films for Modd compound release. (Fig. 10).