Evaluation Study of in-situ Gel Using Catanionic Surfactant Mixtures

D.R. Mundhada¹*, Dr A.V. Chandewar²

¹Research Scholar, P. Wadhawani College of Pharmacy, Yeotmal,

²Principal, P. Wadhawani College of Pharmacy, Yeotmal

*Corresponding Author E-mail: drmundhada@yahoo.com

Abstract:

The present study described the gelation temperature, gelation time, viscosity study, pH, properties of thermosensitive gel prepared of poloxamer 407 and carbopol 934P which are not affected by the concentration of each component. i.e. addition of Drugs or reference catanionic mixture. The use of Catanionic drug-surfactant mixtures was proven to be an efficient novel method of obtaining sustained drug release from Insitu gels. The effects of changes in the pH and ionic strength on the catanionic aggregates was also investigated, and this method of sustaining the release was found to be quite resilient to variations in both. Although the phase behavior was somewhat affected, large micelles and vesicles were still readily found. The drug release was significantly sustained even under NaCl. Comparing the diffusion coefficients for drugs being released from gels with those for drugs from catanionic mixtures in gels revealed differences in the order of magnitude of 10 to 100. This means that the release of a drug can be extended over time, for example, from 30 minutes to 12 hours, potentially improving both the efficiency of the formulation and the patient compliance.

KEY WORDS: Catanionic drug-surfactant mixtures, gelation temperature, gelation time, viscosity study, poloxamer 407, carbopol 934P.

1. Introduction:

A gel is a two-component, cross linked three-dimensional network consisting of structural materials interspersed by an adequate but proportionally large amount of liquid to form an infinite rigid network structure which immobilizes the liquid continuous phase within¹. The development of in situ gel systems has received considerable attention over the past few years. In the past few years, increasing number of in situ gel forming systems have been investigated and many patents for their use in various biomedical applications including drug delivery have been reported². In situ gel formation occurs due to one or combination of different stimuli like pH change, temperature modulation and solvent exchange³.

1.1 Approaches for in situ gelling system⁴:

The various approaches for in situ gelling system are:

A. Stimuli-responsive in situ gel system

-Temperature induced in situ gel systems

- pH induced in situ gel systems

B. Osmotically induced in situ gel systems (Ion‐activated systems)

C. Chemically induced in situ gel systems

-Ionic cross linking

-Enzymatic cross linking

-Photo-polymerization

1.2 Polymers used as in situ gelling agents⁵:

Materials that exhibit sol to gel transition in aqueous solution at temperatures between ambient and body temperature is of interest in the development of sustained release vehicles with in situ gelation properties

Some of the polymers used as in situ gelling agents are:

• Gellan gum

• Alginic acid

• Pluronic F127

• Xyloglucan

• Pectin

• Xanthum gum

• Chitosan

• Carbomer

2. MATERIAL AND METHOD:

Dexamethosone, Ketorolac Trimethamine, Ondansetron hydrochloride and Zolmitriptan was obtained as gift sample from Hindustan Bioscience Ltd, Hyderabad. Other Material like Benzalkonium Chloride, Lauryl Pyridinium Chloride, Trimathylammonium Bromide and Sodium Dodecyl Sulfate was obtained as gift sample from Qualigen Fine Chemical, Mumbai. Polymer Poloxomer 407 and Carbopol 934P was obtained as gift sample from Sigma Alderich, U.S.A.

3. PRE-FORMULATION STUDY:^6-7

Pre-formulation study was done for the following parameters –

Melting point, pH of drug solution, solubility study, drug-excipients compatibility study, pH of polymer solution.

4. PREPARATION OF GEL⁸

All the gels used in this thesis were prepared at a final concentration of 1% w/v for carbopol 934p and 20% w/v for poloxomer 407 polymer to study gelation temperature, viscosity, pH etc. of gel.

5. RESULTS AND DISCUSSION:^9-10

5.1 Determination of UV absorption maxima

Table 1 : UV Absorption Maxima and R2 (Medium: Phosphate Buffer pH 7.4)

Sr. No.	Drugs	Concentration Range	UV Absorption Maxima	R^2(Standard Calibration Curve)
1	Dexamethosone	1-30 µg/mL	241 nm	0.998
2	Ketorolac	2-20 µg/mL	215 nm	0.996
3	Zolmitriptan	5-100 µg/mL	283 nm	0.996
4	Ondansetron	5-50 µg/mL	246 nm	0.998

5.2 Characterization and identification of drugs:

Table 2: Characterization of Zomitriptan:

Sr. No.	Characterization	Specifications	Result
1	Description	White Powder	Complies
2	Solubility	Water : soluble	Complies
3	Assay	98-102 %	Complies

(http://www.usp.org/sites/default/files/usp_pdf/EN/USPNF/m5354.pdf)

Table 3: Characterisation of Dexamethasone Sodium Phosphate:

Sr. No.	Characterization	Specifications	Result
1	Description	White or slightly yellow, crystalline powder; almost odourless;very hygroscopic.	White Crystalline Powder
2	pH (in 1%w/v solution)	5.7 to 6.7	Complies
3	Solubility	Water : Freely Soluble	Complies
		Methanol : Freely soluble
		Ether : Slightly insoluble
		Chloroform: Very Slightly soluble
4	Specific Optical Rotaion (1% w/v solution)	+75^0 and +83^0	Complies
5	Assay	97 to 103 %	Complies

Table 4: Characterization of Ondansetron Hydrochloride:

Sr. No.	Characterization	Specifications	Result
1	Description	White to off-white powder	Complies
2	Solubility	Freely Soluble in Water and Normal Saline	Complies
3	Assay	98-102 %	Complies

Table 5: Characterization of Ketorolac Tromethamine:

Sr. No.	Characterization	Specifications	Result
1	Description	White or almost white, crystalline powder	Almost white, crystalline powder
2	pH (in 1%w/v solution)	5.7 to 6.7	Complies
3	Solubility	Water : Freely Soluble	Complies
		Methanol : Freely soluble
		Ether : Slightly insoluble
		Methylene chloride : Practcally Insoluble
4	Assay	98.5 to 101.5 %	Complies

5.3 Drugs- excipients compatibility study:

Table 6 Compatibility study of Dexamethasone with Excipients

Conditions	Physical Observations		FTIR Study
	Initial	Final	Initial	Final
Room Temperature	White	White	No changes in main Peak and Match with the Standard	No changes in main Peak and Match with the Standard
At 30^0C and 65% RH	White	White	No changes in main Peak and Match with the Standard	No changes in main Peak and Match with the Standard
At 40^0C and 75% RH	White	White	No changes in main Peak and Match with the Standard	No changes in main Peak and Match with the Standard

Table 7 Compatibility study of Ketorolac with Excipients

Conditions	Physical Observations		FTIR Study
	Initial	Final	Initial	Final
Room Temperature	White	White	No changes in main Peak and Match with the Standard	No changes in main Peak and Match with the Standard
At 30^0C and 65% RH	White	White	No changes in main Peak and Match with the Standard	No changes in main Peak and Match with the Standard
At 40^0C and 75% RH	White	White	No changes in main Peak and Match with the Standard	No changes in main Peak and Match with the Standard

Table 8   Compatibility study of Zolmitriptan with Excipients

Conditions	Physical Observations		FTIR Study
	Initial	Final	Initial	Final
Room Temperature	White	White	No changes in main Peak and Match with the Standard	No changes in main Peak and Match with the Standard
At 30^0C and 65% RH	White	White	No changes in main Peak and Match with the Standard	No changes in main Peak and Match with the Standard
At 40^0C and 75% RH	White	White	No changes in main Peak and Match with the Standard	No changes in main Peak and Match with the Standard

Table 9 Compatibility study of Ondansetron with Excipients.

Conditions	Physical Observations		FTIR Study
	Initial	Final	Initial	Final
Room Temperature	White	White	No changes in main Peak and Match with the Standard	No changes in main Peak and Match with the Standard
At 30^0C and 65% RH	White	White	No changes in main Peak and Match with the Standard	No changes in main Peak and Match with the Standard
At 40^0C and 75% RH	White	White	No changes in main Peak and Match with the Standard	No changes in main Peak and Match with the Standard

In the present study, it has been observed that there is no chemical interaction between all the drugs of reference, the polymers and surfactants used. From the figure 1 to 18, it was observed that there were no changes in these main peaks in IR spectra of mixture of drug and polymers, which show there were no physical interactions because of some bond formation between drug and polymers.

Dexamethasone

Figure 1 - I.R. graph of dexamethosone sodium phosphate(initial)

Figure 2 - I.R. graph of dexamethosone sodium phosphate(Room temperature, after 6 month)

Figure 3 - I.R. graph of dexamethosone sodium phosphate(30⁰C and at 65% relative humidity (RH), after 6 month)

Figure 4 - I.R. graph of dexamethosone sodium phosphate(40⁰C and at 75% RH, after 6 month)

KETOROLAC

Figure 5- I.R. graph of ketorolac tromethamine (initial)

Figure 6- I.R. graph of ketorolac tromethamine (Room temperature, after 6 month)

Figure 7 - I.R. graph of ketorolac tromethamine (30⁰C and at 65% relative humidity (RH), after 6 month)

Figure 8 - I.R. graph of ketorolac tromethamine (40⁰C and at 75% RH, after 6 month)

ZOLMITRIPTAN

Figure 9- I.R. graph of zolmitriptan (initial)

Figure 10- I.R. graph of zolmitriptan (room temperature, after 6 month)

Figure 11- I.R. graph of zolmitriptan (30⁰c and at 65% relative humidity (rh), after 6 month)

Figure 12- I.R. graph of zolmitriptan (40⁰C and at 75% RH, after 6 month)

ONDANSETRON HYDROCHLORIDE

Figure 13 - I.R. graph of ondansetron hydrochloride (initial)

Figure 14 - I.R. graph of ondansetron hydrochloride(room temperature, after 6 month)

Figure 15 - I.R. graph of ondansetron hydrochloride(30⁰c and at 65% relative humidity (rh), after 6 month)

Figure 16 - I.R. graph of ondansetron hydrochloride(40⁰c and at 75% rh, after 6 month)

Figure 17: FT-IR of Poloxamer 407

Figure 18: FT-IR of Carbopol 934P

5.5. Preliminary evaluation parameters:

5.5.1 Gelation temperature of polymer solution:

Gelation temperature is the temperature at which liquid phase makes transition to gel. The formulated gel (Plain, With Drug and with catanionic mixture) were evaluated for Gelation temperature.

5.5.2 pH of polymer solution and Effect of Drugs and Catanionic Mixture on pH and gelation Temperature:

Table 10: Gelation Temperature and pH of formulated Carbopol gel

Sr. No	Gel Formualtions	Gelation Temperature (°C)	pH	Gelation Time (Sec)
1	Plain Carbopol (C)	26.33±0.55	5.36±0.04	56±0.14
2	C+ Dex (C1)	24.32±0.43	5.42±0.14	58±0.16
3	C+Ket (C2)	25.36±0.32	5.34±0.24	60±0.20
4	C+Zolm (C3)	26.10±0.23	5.36±0.42	62±0.18
5	C + Ond (C4)	26.45±0.67	5.29±0.23	57±0.17
6	C +  Ket/SDS (C5)	26.55±0.56	5.45±0.56	59±0.17
7	C + Ond/SDS (C6)	27.38±0.44	5.26±0.45	58±0.14
8	C + LPC/Dex (C7)	26.33±0.39	5.67±0.75	57±0.16
9	C + TTAB/Dex (C8)	27.10±0.56	5.23±0.26	58±0.16
10	C + BAC/Zolm (C9)	26.22±0.63	5.65±0.54	62±0.18
11	C + LPC/Zolm (C10)	26.76±0.22	5.25±0.10	63±0.18
12	C + BAC/Dex (C11)	26.57±0.70	5.23±0.18	58±0.16
13	C + Ket/Dex (C12)	25.88±0.45	5.53±0.17	62±0.18
14	C + Ket/Zolm (C13)	24.90±0.75	5.77±0.38	63±0.18
15	C + TTAB/Zolm (C14)	25.10±0.27	5.56±0.08	58±0.16
16	C + BAC/SDS (C15)	25.23±0.84	5.96±0.27	62±0.18

Table 11: Gelation Temperature and pH of formulated Poloxamer gel

Sr. No	Gel Formualtions	Gelation Temperature (°C)	pH	Gelation Time (Sec)
1	Plain Carbopol (P)	26.76±0.22	5.36±0.04	74.33±4.50
2	P + Dex(P1)	26.57±0.70	5.42±0.14	75.33±4.38
3	P + Ketc (P2)	25.88±0.45	5.34±0.24	77.44±3.36
4	P + Zolm (P3)	26.10±0.23	5.36±0.42	76.33±3.56
5	P + Ond (P4)	26.45±0.67	5.29±0.23	79.23±4.23
6	P + Ket/SDS (P5)	26.55±0.56	5.52±0.04	76.63±5.23
7	P + Ond/SDS (P6)	24.90±0.75	5.77±0.38	74.43±5.30
8	P + LPC/Dex (P7)	25.10±0.27	5.56±0.08	76.33±3.70
9	P + TTAB/Dex (P8)	25.23±0.84	5.96±0.27	78.33±3.80
10	P + BAC/Zolm (P9)	26.33±0.55	5.36±0.04	75.43±3.75
11	P + LPC/Zolm (P10)	24.32±0.43	5.42±0.14	72.33±4.50
12	P + BAC/Dex (P11)	25.36±0.32	5.34±0.24	79.63±4.56
13	P + Ket/Dex (C12)	26.10±0.23	5.36±0.42	76.43±4.50
14	P + Ket/Zolm (P13)	26.45±0.67	5.29±0.23	77.53±4.80
15	P + TTAB/Zolm (P14)	26.67±0.70	5.23±0.28	74.33±4.33
16	P + BAC/SDS (P15)	23.89±0.79	5.83±0.70	75.33±4.57

Each value represents the mean±S.D. (n=3).

The present study described the gelation temperature, gelation time, viscosity study, pH, properties of thermosensitive gel prepared of poloxamer 407 and carbopol 934P were not affected by the concentration of each component. i. e addition of Drugs or reference catanionivc mixture.

5.6 Formation of catanionic aggregates with oppositely charged surfectants:

The mixtures of SDS and two different cationic drugs were studied. The drugs used were ketoralac and ondansetron, for which extensive, though simplified, ternary phase diagrams were composed (see Figure 19)

The white area symbolizes precipitates, the grey ones symbolize micellar/aqueous solution, the black areas symbolize vesicles and the striped ones represent multi-phase regions. The pH was left unadjusted when constructing both diagrams. The left phase diagram shows the three-component system containing ketorolac, SDS and physiological sodium chloride solution and the right one shows the system containing ondansetron, SDS and physiological sodium chloride solution.

Figure 19 Phase diagrams.

Although the ketoralac/SDS and the ondansetron/SDS system resemble each other to a certain extent, there is one large difference: the ketoralac/SDS system has a vesicle area only on the SDS rich side, whereas the ondansetron/SDS system has one vesicle area on each side of the equimolar line. Tjis is the indicative of In both systems of ondansetron, however, vesicles and large micelles were found, Vesicles and micelles characteristic for most of the catanionic drug-surfactant systems examined are shown in Figure 20.

Figure 20. Cryo-TEM micrographs of (left) vesicles in a 14/26 mM ondansetron/SDS solution and (right) micelles in an 8/32 mM ketoralac/SDS solution. The bars show 200 nm.

Interestingly, the micrographs on the micelles do not only show elongated micelles, but also branched ones, as indicated by the arrows in Figure 20. However, cryo-TEM is an excellent method for qualitatively studying the appearance of the different structures present, but not quite so good when it comes to quantifying the structures. A rheological study was, therefore, performed, as shown in Figure 21.

In further study, the number of drugs tested for catanionic formation was increased by two, to a total number of four. The selection criterion for this study was that the drugs should have either a positive or a negative charge and that their structure should “look” as though it would be surface active. The results from this study showed that both positively and negatively charged drug compounds were able to form catanionic mixtures when mixed with different oppositely charged surfactants (see Table 12).

Figure 21. The viscosity of some of the compositions examined in the Ketorolac/SDS system, The concentration SDS is plotted along the x-axis, whereas the corresponding ketorolac concentration is specified for each sample examined. Filled symbols represent vesicle phase and open symbols represent micellar/aqueous solution.

Table 12. The occurrence of catanionic interactions tabulated according to systym examined.

Cationic component	Catanionic interactions	Catanionic vesicles	Catanionic high-viscosity micelles	Anionic component
Ketoralac	X	X	X	SDS
Ondansetron	X	X	X	SDS
LPC				Dexamethosone
TTAB				Dexamethosone
BAC	X			Zolmitriptan
LPC	X			Zolmitriptan
BAC	X			Dexamethosone
Ketoralac	X			Dexamethosone
Ketoralac	X			Zolmitriptan
TTAB	X		X	Zolmitriptan
BAC	X			SDS

Figure 22. An example of drug release profiles. To the left is the ketoralac/SDS system, where (1) marks  the 14 mM ketoralac reference in 1% C940, (2) is the 8/32 mM micellar composition in 1% C940 and (3) is the 14/26 mM vesicular composition in 1% C940. To the right is the ondansetron/SDS system, where (1) marks the 14 mM ondansetron reference in 1% Poloxomer, (2) is 14 mM ondansetron reference in 1% C940, (3) is the 26/14 mM vesicular composition in 1% Poloxomer, (4) is the 14/26 mM vesicular composition in 1% C940 and (5) is the 14/26 mM vesicular composition in 1% Poloxomer.

5.7 In vitro drug Release:

5.7.1 Release Study of Drugs from Catanionic Aggregates from Gel 

The  several  compositions  of  four  different  catanionic  drug surfactant systems were tested to examine the extent of the prolongation of the drug release All systems examined indicated that using catanionic systems is a very efficient method of obtaining prolonged release from gels.

Some drug release results are shown in Figure 22.

Rheological measurements were performed to investigate to identify any catanionic effects on the Carbopol gels. The micrographs, some of which are shown  in Figure 23, confirmed  that  both  the  vesicles  and  the  micelles seemed unaffected by the presence of the polymer.

Figure 23. Cryo-TEM micrographs of (left) vesicles in a 14/26 mM ondansetron/SDS mixture and (right) micelles in an 8/32 mM ketoralac/SDS mixture, both in 1% C940. The bar indicates 200 nm.

Figure 24 An illustration of the extent to which the drug release was slowed for the different catanionic mixtures.

A demonstration of the diffusion coefficients for each mixture examined, compared with its corresponding reference, is shown in Figure 24.

Each column shows the reference diffusion coefficient (i.e., when the drug was not mixed with an oppositely charged surfactant) divided by the diffusion coefficient from the catanionic mixture indicated on the xaxis and therefore provides a direct comparison of the relative increase in the timeover which the drug is released. The bars show the confidence interval for each comparison.

5.8 Electrodynamic investigations

The diffusion was investigated in two 1% C940 gels, one containing  only 14  mM  ketoralac  and  the  other  containing a 14 mM ketoralac / 26 mM SDS vesicle mixture. The methods used in this investigation were dielectric spectroscopy and transient current measurements. The aim of the study was actually two-fold, to explore the release mechanism of course, but also to determine whether these methods could be applied as characterization tools at all in this instance. In dielectric spectroscopy, a sinusoidal voltage is applied across the sample between two electrodes, whilst varying the frequency of the applied voltage. In the transient current measurements, the same set-up was used, but a constant voltage step was applied.

Figure 25. Current response from a 1% C940 gel containing 14 mM ketorolac, after application of a potential step from 0-1 V. Two exponentially decaying regions are apparent.

Figure 26 is a plot of the results from the transient current measurements performed on the gel containing the 14 mM ketorolac and 26 mMSDS vesicle composition.

Figure 26. Current response from a 1% C940 gel containing 14 mM ketorolac and 26 mM SDS, after application of a potential step from 0-1 V.

6. CONCLUSION:

The present study described the gelation temperature, gelation time, viscosity study, pH, properties of thermosensitive gel prepared of poloxamer 407 and carbopol 934P were not affected by the concentration of each component. i. e addition of Drugs or reference catanionic mixture. it has been observed that there is no chemical interaction between all the drugs of reference, the polymers and surfactants used. From the figure 1 to 18, it was observed that there were no changes in these main peaks in IR spectra of mixture of drug and polymers, which show there were no physical interactions because of some bond formation between drug and polymers.

7. REFERENCES:

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Received on 21.07.2016       Modified on 23.08.2016

Accepted on 30.08.2016      ©A&V Publications All right reserved

Research J. Science and Tech. 2016; 8(4):165-178.

DOI: 10.5958/2349-2988.2016.00025.5