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 Table of Contents  
ORIGINAL ARTICLE
Year : 2012  |  Volume : 4  |  Issue : 2  |  Page : 155-163  

Development of span 80-tween 80 based fluid-filled organogels as a matrix for drug delivery


Department of Biotechnology and Medical Engineering, National Institute of Technology, Rourkela, India

Date of Submission10-Mar-2011
Date of Decision07-Jun-2011
Date of Acceptance14-Aug-2011
Date of Web Publication10-Apr-2012

Correspondence Address:
Kunal Pal
Department of Biotechnology and Medical Engineering, National Institute of Technology, Rourkela
India
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Source of Support: National Institute of Technology, Rourkela, India, Conflict of Interest: None


DOI: 10.4103/0975-7406.94822

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   Abstract 

Background: Organogels are defined as 3-dimensional networked structures which immobilize apolar solvents within them. These gelled formulations are gaining importance because of their ease of preparation and inherent stability with improved shelf life as compared to the ointments. Aim: Development of span 80-tween 80 mixture based organogels for the first time by fluid-filled fiber mechanism. Materials and Methods: Span 80 and tween 80 were used as surfactant and co-surfactant, respectively. The surfactant mixtures were dissolved in oil followed by the addition of water which led to the formation of organogels at specific compositions. The formulations were analyzed by microscopy, X-ray diffraction (XRD), time-dependent stability test and accelerated thermal stability test by thermocycling method. Ciprofloxacin, a fourth-generation fluoroquinolone, was incorporated within the organogels. The antimicrobial activity of the drug loaded organogels and in vitro drug release from the gels was also determined. Results and Conclusions: Microscopic results indicated that the gels contained clusters of water-filled spherical structures. XRD study indicated the amorphous nature of the organogels. The release of the drug was found to be diffusion controlled and showed marked antimicrobial property. In short, the prepared organogels were found to be stable enough to be used as pharmaceutical formulation.

Keywords: Antimicrobial activity and drug release, organogel, span 80, tween 80


How to cite this article:
Bhattacharya C, Kumar N, Sagiri SS, Pal K, Ray SS. Development of span 80-tween 80 based fluid-filled organogels as a matrix for drug delivery. J Pharm Bioall Sci 2012;4:155-63

How to cite this URL:
Bhattacharya C, Kumar N, Sagiri SS, Pal K, Ray SS. Development of span 80-tween 80 based fluid-filled organogels as a matrix for drug delivery. J Pharm Bioall Sci [serial online] 2012 [cited 2019 Jul 23];4:155-63. Available from: http://www.jpbsonline.org/text.asp?2012/4/2/155/94822

Organogels may be defined as a gelled system in which the external organic phase has been immobilized by the 3-dimensional network formed by the organogelators. The formation of the networked structure may be attributed to the physical or covalent interactions amongst the gelator molecules. In general, physical gels show gel-to-sol phase transition (Tg). [1],[2],[3] This property is not shown by the gels formed due to chemical reactions. Tg has been determined by various methods including "dropping ball" technique, [4] bubble motion [5] or by the inverted test tube method. [6] The physical gels show shear thinning behavior and can be best explained by plastic flow behavior. [7] During the formation of physical organogels, there is an increase in the viscosity as aqueous phase is added to the apolar solution of the amphipaths. The classical example of this phenomenon includes lecithin organogel where the increase in the viscosity is approximately 10 4 -10 6 -fold. [8,9] Most organogels are isotropic in nature and do not allow polarized light to pass through them. [10],[11],[12] The increased applications of organogels as delivery vehicles in cosmetics, nutraceutical and pharmaceutical industries may be attributed to the thermostable nature of the organogels with improved shelf life. [13],[14] Depending on the composition of the organogels, they may be either transparent or opaque. The lecithin organogels are transparent in nature while the sorbitan monostearate organogels are opaque in nature. [9],[15],[16],[17] Till recent past, most organogels were developed using components which were not regarded as biocompatible. Keeping the long-term stability and the ability of the organogels to accommodate both lyophilic and lyophobic agents in mind, scientists are working toward the development of organogels with improved biocompatibility. [17] This has added a new dimension in the food and pharmaceutical industries because of the easy preparation of the organogels. [18] The current study reports the development and characterization of the span 80-tween 80 mixture based organogels. To the best of the knowledge of the authors, the development of the organogels using span 80-tween 80 mixtures has not been reported till date.


   Materials and Methods Top


Materials

Span 80 (sorbitan monooleate) was procured from Loba chemie, Mumbai, India. Tween 80 (polyoxyethylene sorbitan monooleate), rhodamine B and tetracycline hydrochloride were procured from Himedia, Mumbai, India. Ciprofloxacin was obtained from Fluka Biochemika, China, and metronidazole was a gift from Aarti Drugs, Mumbai, India. Edible sunflower oil was purchased from the local market. Dialysis tubing (molecular weight cutoff: 50 kDa) was purchased from Himedia, Mumbai, India. All the experimental samples were prepared using double-distilled water.

Methods

Organogel preparation

Surfactant mixtures of span 80 and tween 80 were prepared so as to have span 80:tween 80 ratios of 1:1 (G-organogels), 1:2 (H-organogels) and 1:3 (I-organogels). Specified amounts of the surfactant mixtures were added to specified volume of sunflower oil in 15-ml culture bottles kept on magnetic stirrer. The above mixture was stirred for 20 min. Subsequently, water was added drop by drop to the surfactant-oil solution with the use of a burette until the formation of organogel or until the total fraction of water has reached 80% of the volume of the surfactant-oil-water mixture. Based on the composition of the surfactant-oil-water mixture, the systems either formed gelled structures or remained as a liquid mixture. A ternary phase diagram was plotted to find the area of the gelation. Origin 8 (Professional) software was used to plot the ternary plot.

Samples for morphology and microscopic studies were prepared in a similar manner except the use of 0.01% (w/v) rhodamine B solution in water as the aqueous phase.

The samples containing antimicrobial drugs were prepared by using drug (ciprofloxacin, metronidazole or tetracycline) suspension in oil. The rest of the procedure for the preparation of the organogels was same. The final composition of the drugs in the organogel was 1% (w/w).

Characterization of organogels

The compositions of all the prepared organogels by the above said method are summarized in [Table 1]. Of these, three samples of organogels, one each from G, H and I groups, i.e. G_1, H_1, I_1, were used for the further characterization of the organogels.
Table 1: Composition of the organogels used for stability tests

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Macroscopic study

The samples prepared with aqueous rhodamine B solution were visually examined to understand the phenomenon of the gelation. The photographs of the samples were taken with a 10 megapixel Canon DSLR camera.

Microscopic study

The samples were observed under Hund, Wetzlar Light microscope (H-600, Germany) coupled with JVC color video camera (TK-C1381, Japan). H_1 organogel was observed under Zeiss confocal microscope (LSM 500, Germany) and environmental scanning electron microscope (ESEM) (Quanta 200, FEI Company, The Netherlands).

XRD analysis

X-ray diffraction (XRD) analysis was carried out for G_1, H_1, I_1 and H_1 + D (H_1 organogel containing 1% ciprofloxacin) and ciprofloxacin. The test was performed using Cu-Kα source, with the machine operating at 30 kV and 20 mA. The samples were scanned within the range of 10°-50° 2θ at a rate of 2° 2θ per minute.

Rheological study

Rheological studies of the organogel samples were carried out using cone and plate viscometer (BOHLIN VISCO-88, Malvern, UK). The diameter of the cone was 30 mm and had an angle of 5.4°. A gap of 0.15 mm and a temperature of 25°C were maintained throughout the experiment. The samples were subjected to a shear rate sweep starting from 10 to 60 sec−1 . The results were obtained in triplicate.

Sol-gel transition study

The organogels were heated in a temperature-controlled water bath (Lauda Ecoline, RE104, Germany). The experiment was started at 30°C and the temperature was increased up to 80°C with an increment of 5°C. The samples were incubated at the specified temperature for 5 min and were observed by inverted test tube method. The temperature at which the gel started to flow was regarded as gel-to-sol transition. The study was done in triplicate.

Accelerated stability testing

Freshly prepared samples were subjected alternatively to temperatures of 50°C and −20°C for a period of 15 min. The experiment was carried out for 8 h. The samples were analyzed visually for any instability.

Stability studies on a time scale

The freshly prepared samples were kept at the ambient temperature (AT), 5°C and 37°C. The samples were visually observed at regular intervals of time for any instability.

In vitro drug release studies

Accurately weighed 1 g of the organogel samples (G_1 + D, H_1 + D, I_1 + D), containing 1% (w/w) ciprofloxacin, were put into dialysis tubings (molecular weight cutoff: 50 kDa), whose one end was secured by a knot. After filling the samples within the tubing, the other end was also secured by a knot. The tubings were dipped into a beaker containing 50 ml of double-distilled water, which served as a dissolution medium. Until the first hour completion, the sample tubings were taken out from the beaker and were put into another beaker containing fresh 50 ml of water at every 15 min interval. After 1 h, the changeover was done at an interval of 30 min. Two milliliters of the dissolution medium containing the drug was collected at the above-mentioned intervals in a test tube for further studies and the rest was discarded. The experiment was carried out for a period of 8 h. By using the collected samples, the amount of ciprofloxacin released from the organogels into the dissolution medium was measured at λmax of 237 nm using UV-visible spectrophotometer (Shimadzu UV 1601 r). The experiments were carried out in triplicates.

Antimicrobial test

Gram-positive bacterium Bacillus subtilis (MTCC 121) and gram-negative bacterium  Escherichia More Details coli (NCIM 5051) were used for antimicrobial study using nutrient agar solid medium as the culture medium. Warm, sterilized medium was poured into the Petri plates and was allowed to solidify. One milliliter of the cell suspension (containing 10−6 to 10−7 cfu/ml, approx.) was spread over the surface of the nutrient solid agar medium. Thereafter, wells of diameter 9 mm were made into the agar plates using a borer to accommodate 0.5 g of antimicrobial loaded H_1 organogels. The Petri plates were incubated at 35°C for 18 h. The zone of inhibition was measured by a ruler. The H_1 samples of organogels without drug served as control for the counterpart with drug.


   Results and Discussion Top


Preparation of the organogels

The organogels were prepared by dissolving the surfactant mixture in sunflower oil followed by the addition of water. With the initial addition of water, the mixture turned into a white turbid solution. As further amount of water was added, the samples either formed a gelled structure or remained as turbid solution. The samples were regarded as organogels if the surfactant-sunflower oil-water mixture did not flow when the culture bottles were inverted [Figure 1]. The samples which formed gelled structures released heat, indicating an exothermic reaction as the gels were developed. This indicates that the samples attain low energy state as they undergo transition into gelled structures and may be regarded as thermodynamically stable. In general, the developed organogels were white to pale yellow in color depending on the composition and were opaque in nature. They were having slight odor and were oily to touch.th

Ternary phase diagrams were prepared for the G, H and I type organogels [Figure 2]. Each arm of the phase diagram represents the proportion of a particular component. The formation of the organogel was dependent on the concentration of all the three components, viz. surfactant mixture, sunflower oil and water. From the experimental results, it can be concluded that the composition of the surfactant mixture played an important role in governing the phenomenon of gelation as can be visualized from the area of gelation in the ternary phase diagram. [Table 2] identifies the % gelled area, given by the formula:

Figure 1: Organogel samples of different composition

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Figure 2: Ternary phase diagrams of the (a) G, (b) H and (c) I organogels

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Table 2: Percentage gelled area of the organogel groups

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where W G = weight of the paper representing the gelled area and W T = weight of the paper representing the total area.

Initially, the % gelation area increased from G to H type organogels. It may be attributed to the increase in the tween 80 (water soluble surfactant) fractions, which may result in the increased water uptake, thereby resulting in the increased gelled phase. [12] With the further increase in the tween 80 fraction from H to I type organogel, there was a slight decrease in the % gelled area. This may be attributed to the further increase in the hydrophilicity with the subsequent alteration in the intergelator hydrophobic bonding. [19]

Macroscopic study

The macroscopic study was done by using the samples whose aqueous phase contained rhodamine B solution. [Figure 3] indicates that the aqueous phase constitutes the internal phase, indicating that the organogel is a water-in-oil emulsion. From [Figure 3], it seems that the surfactant molecules self-assembled into spherical shaped structures, [16] which then underwent physical interactions so as to form agglomeration of the self-assembled structures resulting in the formation of a networked structure. The networked structure, so formed, immobilized the external oil phase, leading to the formation of the organogel. The gels were oily to touch which confirmed that the external phase is apolar in nature.
Figure 3: Morphological observation of (a) G_1, (b) H_1 and (c) I_1 organogels

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Microscopic study

Light microscopy revealed that G_1, H_1 and I_1 organogels are having granular structures [Figure 4]. But the main problem with the light microscope is that it provides images from all the focal lengths. Hence, no conclusion could be drawn from the micrographs. Subsequently, the samples were analyzed under confocal and environmental electron scanning microscopes [Figure 5]. The micrographs indicated the presence of aggregated granular structures which lead to the formation of a 3-dimensional network structure. [16] The apolar fluid phase remained entrapped within this gelled network. [17] With the increase in the concentration of surfactant mixture, there was a corresponding increase in the 3-dimensional networked structure as visualized under light microscope [Figure 4]. [20]
Figure 4: Micrographs of (a) G_1, (b) H_1 and (c) I_1 organogels without rhodamine B

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Figure 5: Micrographs of H_1 organogel as visualized under (a) confocal microscope and (b) ESEM

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XRD analysis

The XRD profile of the organogels and ciprofloxacin is shown in [Figure 6]. The XRD of ciprofloxacin alone indicated sharp peaks at 10.4°, 11.2°, 13.5°, 14.5°, 16.5°, 17.8°, 19.2°, 20.8°, 22.2°, 22.6°, 23.3°, 24.5°, 25.4° and 26.5° 2θ. The presence of sharp peaks indicates the crystalline nature of ciprofloxacin, which may be attributed to the highly ordered molecular structure. The G_1, H_1 and I_1 organogels showed a broad peak at 20° 2θ (approx.), though the intensity of the peaks and the profile for the diffractogram were considerably different. The presence of the peaks at the same position indicates that the composition of the organogels is same. The H_1 + D organogel also showed a broad peak at 20° 2θ. This indicates that either ciprofloxacin is present as solution in oil or present within the networked structure of the gelators. It was found experimentally that 1% (w/v) ciprofloxacin in sunflower oil forms a suspension, which indicates that the suspended ciprofloxacin got entrapped within the networked structure and was not available on the surface for detection by XRD technique.
Figure 6: XRD graphs of G_1, H_1, I_1, H_1 + D and ciprofloxacin

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The width of the peak at half maximum (FWHM) is dependent on the crystallinity of the sample, which in turn is dependent on hydrophobic interactions amongst the gelator molecules responsible for the formation of an ordered structure. For the determination of the FWHM, the XRD profile data was smoothened using Savitzky-Golay filter. The smoothening was done using 50 points of window and polynomial order of 5. Subsequently, the smoothened curve was normalized and the width of the curve at 50% normalized intensity was calculated which gave the FWHM [Figure 7]. The FWHM for the G_1, H_1, I_1 and H_1 + D was found to be 9.5, 8.28, 9.39 and 10.66, respectively. In general, lower FWHM values indicate higher crystallinity and vice versa. This indicates that there is an initial increase in the crystallinity with a subsequent increase in tween 80. But as the proportion of tween 80 is further increased, there is a reduction in the hydrophobic interactions, resulting in a decrease in the intensity of the peak of the I_1 organogel. The FWHM of the H_1 + D organogels was highest (10.66), supporting the fact that the ciprofloxacin molecules are present within the networked structures and interact with the gelator molecules, thereby resulting in the decrease in the interactions amongst the gelator molecules. This result shows decrease in the ordered structure of the organogels, and hence the increased FWHM.
Figure 7: Normalized XRD graphs of G_1, H_1, I_1 and H_1 + D organogels

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Rheological study of the organogel

The viscosity profile of the organogels indicates a decrease in the viscosity of the organogels with an increase in the shear rate [Figure 8]. The viscosity profile of the organogel showed an elastic phase followed by a non-elastic phase. The presence of the elastic phase may be attributed to the elastic nature of sorbitan ester organogels. [12] In this region, the physical interactions amongst the gelator molecules are stronger and the applied shear is not able to dislodge the gelator molecules involved in the formation of the gelled structures via fluid-filled microstructures. As the applied shear is increased, the hydrophobic interactions are not able to keep the fluid-filled microstructures together. This results in the transition of the system from the gelled phase to the free-flowing liquid phase, marked by the disruption of the 3-dimensional networked structures. [12]
Figure 8: Viscosity profile of the organogels

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Thermal study

The organogels were subjected to increasing temperatures starting from 30°C. An increment of 5°C was made after 5 min incubation at the previous temperature. The samples were considered to have undergone gel-sol transition when they started to flow (determined by inverted test tube method). The gel-to-sol transition temperatures were found to be at 60°C, 70°C and 65°C for G_1, H_1 and I_1 organogels, respectively [Figure 9]. As the temperature is increased, there is a corresponding increase in the surface free energy with a subsequent increase in the mobility of the self-assembled structures formed by the gelators. With further increase in the temperature, the interaction amongst the self-assembled structures gets abolished, and hence results in the disruption of the networked structure, which causes the system to flow freely. [16] The results are in conjunction with the XRD results, which showed highest crystallinity for H_1 followed by I_1 and G_1. The energy needed for the disruption of a gel is expected to be higher, so as the samples with higher crystallinity. The organogels loaded with ciprofloxacin showed lower transition temperatures of 55°C, 65°C and 60°C for G_1 + D, H_1 + D and I_1 + D organogels, respectively [Figure 9]. This may be attributed to the interaction of the ciprofloxacin molecules with the gelator molecules, resulting in decreased interaction amongst the gelator molecules.
Figure 9: Gel-sol transition temperatures of organogels

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Accelerated stability testing

The accelerated stability testing of the G_1, H_1 and I_1 organogels was carried out by the thermocycling method. The organogels may be considered as water-in-oil emulsion. Emulsions, in general, are considered as a complex system whose stability cannot be studied by Arrhenius relationship which is usually used for stability testing of various simple pharmaceutical, nutraceutical and cosmetic formulations. The simplest method of conducting the same is to use a freeze-thaw method. The method employs continuous exposure of the samples to a freeze-thaw cycle at short intervals of time. The freezing temperature should be ≤−5°C, whereas the thawing temperature is dependent on the type of formulation. This method only provides a prediction and does not give us an absolute value. This has been attributed to the process of destabilization only during freeze-thaw cycles and not under storage conditions. [21] The testing considers the probable change in the properties of the surfactants at elevated temperatures, which in turn may alter the partitioning property of the surfactant and the probable rupture of the surfactant layer in the presence of ice crystals at lower temperatures. In either of the case, the samples will become unstable. In general, it is considered that the samples should withstand at least five cycles of freeze-thawing process. [22] The developed organogels were able to sustain much more than five cycles, indicating their inherent stability. The observations of the experiment are tabulated in [Table 3].
Table 3: Observations of the accelerated stability test

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Stability studies on time scale

The samples of organogels were kept at AT, 5°C and 37°C. The composition of the samples used for the stability studies is given in [Table 1]. The observations of the test are reported in [Table 4], [Table 5], and [Table 6]. In general, it was found that the samples kept at 5°C were stable for a prolonged period of time. The samples kept at 37°C showed destabilization of the organogels within a period of 1 week, whereas the samples kept at AT showed stability for an intermediate period of time. The H_1 organogels were more stable for prolonged periods of time at AT compared to others. This may be attributed to the crystallinity of the sample. The stability and % crystallinity of organogels follow the same order, i.e. H_1 > I_1 > G_1. The study indicates that if the developed organogels are stored either in a cold or cool place, they can have considerably longer shelf life and may be used in formulating drug delivery systems.
Table 4: Observations of the stability test for G organogels

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Table 5: Observations of the stability test for H organogels

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Table 6: Observations of the stability test for I organogels

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In vitro drug release

The release rate of drug from organogel systems depends on the drug partition coefficient and drug solubility in the oil and aqueous phases. [11] Ciprofloxacin as a model drug was incorporated within organogels and its release rate was studied. G_1 + D [G_1 organogel containing 1% (w/w) ciprofloxacin] organogel showed maximum percentage of drug release at the end of 8 h, followed by the release of the drug from I_1 + D [I_1 organogel with 1% (w/w) ciprofloxacin] and H_1 + D [H_1 organogel with 1% (w/w) ciprofloxacin] organogels [Figure 10]. With the increase in crystallinity of the organogel, there is a decrease in the release behavior of the drug. As the crystallinity of samples increases, there is a corresponding increase in the crystallite regions which act as crosslinked sites, and hence an increase the crosslinking density. [11] The hindrance to the diffusion of solutes is higher in matrices with higher crosslinking density. This results in the decrease in the flux of the drug from the organogel. This phenomenon is confirmed in majority of the reported systems. [23] As per XRD results, the H_1 organogels are more crystalline than the others and these results are in accordance with the in vitro drug release pattern of the gels. The % cumulative release of the drug from H_1 + D organogels is about 5% compared to I_1 + D's 12% and G_1 + D's 18% of the total drug incorporated. The G_1 organogels are less crystalline, so they have released the drug in higher concentrations in vitro. The order of % cumulative drug release is G_1 + D > I_1 + D > H_1 + D.
Figure 10: In vitro drug release data for ciprofloxacin

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Antimicrobial studies

The bioactive agents having antimicrobial properties were incorporated within the organogels. A bore of 9 mm diameter was made in the nutrient agar plates containing the specific microorganism. [Table 7] shows the results of the test. It was found that the bioactive agents were able to diffuse out of the organogels and showed their antimicrobial property for a period of 18 h. On the other hand, control organogel samples did not show any zone of inhibition. This indicates that the organogels may be used as a controlled delivery system, where they can deliver the bioactive agents for a prolonged period of time.
Table 7: Antimicrobial test results

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   Conclusion Top


This study reports the successful development of novel span 80-tween 80 mixture based organogels for the first time. The gels were developed by fluid-filled mechanism. The developed organogels were found to be stable in nature and were able to sustain heat shocks for prolonged period. The drug release study from the organogels indicated diffusion-dependent release. Since the organogels were prepared using FDA approved components, the organogels are expected to be biocompatible. Based on the preliminary studies, it seems that the span 80-tween 80 mixture based organogels may be tried as a drug carrier for transdermal bioactive agent delivery.


   Acknowledgments Top


The authors acknowledge the funding received from National Institute of Technology, Rourkela, India, during the completion of the work. Authors also express their thanks to Prof. G. R. Satpathy, Prof. B. P. Nayak and Prof. S. Paria for giving access to their laboratory during the study.

 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]


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Julian R. Silverman,George John
Journal of Agricultural and Food Chemistry. 2015; 63(48): 10536
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5 Effects of micro and nano ß-TCP fillers in freeze-gelled chitosan scaffolds for bone tissue engineering
Nadeem Siddiqui,Krishna Pramanik
Journal of Applied Polymer Science. 2014; 131(21): n/a
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6 Palm oil-based organogels and microemulsions for delivery of antimicrobial drugs
Suryakant Pradhan,Satish S. Sagiri,Vinay K. Singh,Kunal Pal,Sirsendu S. Ray,Dillip K. Pradhan
Journal of Applied Polymer Science. 2014; 131(6)
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7 Development and Characterization of Sorbitan Monostearate and Sesame Oil-Based Organogels for Topical Delivery of Antimicrobials
Vinay K. Singh,Krishna Pramanik,Sirsendu S. Ray,Kunal Pal
AAPS PharmSciTech. 2014;
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8 Guar gum and sesame oil based novel bigels for controlled drug delivery
Vinay K. Singh,Indranil Banerjee,Tarun Agarwal,Krishna Pramanik,Mrinal K. Bhattacharya,Kunal Pal
Colloids and Surfaces B: Biointerfaces. 2014;
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9 An innovative hydrogel of gemcitabine-loaded lipid nanocapsules: when the drug is a key player of the nanomedicine structure
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Soft Matter. 2014; 10(11): 1767
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10 Thermal, electrical, and mechanical properties of tween 80/span 80-based organogels and its application in iontophoretic drug delivery
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Journal of Applied Polymer Science. 2014; : n/a
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11 Development and Characterization of Soy Lecithin and Palm Oil-based Organogels
Nirod Baran,Vinay K. Singh,Kunal Pal,Arfat Anis,Dillip K. Pradhan,Krishna Pramanik
Polymer-Plastics Technology and Engineering. 2014; 53(9): 865
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12 Stability mechanisms of liquid water-in-oil emulsions
F.Y. Ushikubo,R.L. Cunha
Food Hydrocolloids. 2014; 34: 145
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13 Olive oil based novel thermo-reversible emulsion hydrogels for controlled delivery applications
Vinay K. Singh,Sowmya Ramesh,Kunal Pal,Arfat Anis,Dillip K. Pradhan,Krishna Pramanik
Journal of Materials Science: Materials in Medicine. 2014; 25(3): 703-721
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14 Encapsulation of animal wax-based organogels in alginate microparticles
Sai S. Sagiri,Kunal Pal,Piyali Basak
Journal of Applied Polymer Science. 2014; : n/a
[Pubmed] | [DOI]
15 Development of mustard oil- and groundnut oil-based span 40 organogels as matrices for controlled drug delivery
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Designed Monomers and Polymers. 2013; : 1
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16 Castor oil and sorbitan monopalmitate based organogel as a probable matrix for controlled drug delivery
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Journal of Applied Polymer Science. 2013; 130(3): 1503
[Pubmed] | [DOI]



 

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