Development and Method Validation of an Unconventional In-Vitro Test To Measure Mucoadhesive Strength of Tablets

 

Mohammed M Hussain* and Nappinai M

Pharmaceutics Dept, C.L.Baid Metha College of Pharmacy, Jyothi Nagar, Rajivegandhi Road,

Chennai 600097. India

*Corresponding Author E-mail:  hussainpublication@gmail.com

 

ABSTRACT

The mechanism of mucoadhesion involves the interpenetration of the mucus with other molecules strengthened by the formation of secondary chemical bonds between them. Literature survey showed that sophisticated instruments are required for measurement of mucoadhesive force. This work was undertaken to develop and validate a simple, economic, rapid, accurate, reproducible method for measurement of the same. A simple, unconventional test procedure using rat and sheep stomach tissues (as biological substrate) was standardized. The detachment forces per surface area in Newton/millimeter2 are reported. Mucoadhesive tablets were used as test samples for development and validation of this method.

 

KEYWORDS: Mucoadhesion, Modified balance, Mucoadhesive tablets, Detachment force.

 


INTRODUCTION:

In recent years, considerable interest has been shown in the use of mucoadhesive dosage forms with regard to enhancing the local and systemic administration of peptides and other poorly absorbed drugs from the gastrointestinal tract. The term 'bioadhesion' is used to define the attachment of synthetic or natural macromolecules to a biological substrate. When the substrate is a mucosal epithelium, this phenomenon is referred to as 'mucoadhesion'1

                          

Bioadhesiveness is the vital for optimizing performance for the the tablet containing excipients which has this property. There are many methods and instruments to measure the adhesive force and their reports of the same2.

                         

The present study, however a cost effective, simple, precise, accurate, reproducible method for the evaluation will benefit researchers. Hence the experimental technique was modified from a previously published method2. The modifications were executed in instrumental setup using simple glass wares, metal wires and weights.

 

2. MATERIALS AND METHODS:

2.1 Materials:

Rifampicin B.P was obtained as a gift sample from Spic pharma Chennai. Psyllium husk was obtained as a gift sample from Nileshwari Enterprises, Mumbai.

 

Carbopal 934, Sodium carboxymethylcellose (high viscosity), Sodium alginate, Sodium bi carbonate, Hydrochloric acid AR, Sodium hydroxide, and HPMC K100, Chitosan-H  were purchased from S.D Fine Chemicals Ltd, Mumbai and Rolex Laboratories, Chennai respectively. Poly methacrylic acid ethylacrylate, PVP-K30, talc, magnesium stereate were obtained as a gift sample from Fourts India Pvt Ltd, Chennai. 

 

2.2 Tissues collection:

2.2.1 For rat: The stomach tissue was removed intact  from the rat and immediately immersed in pH 7.4 phosphate buffer with glucose (1 % w/v) and stored under ice-cold condition.

2.2.1 For sheep: Immediately after slaughter, the stomach tissue was removed from sheep and transported to laboratory in tyrode solution2.

 

2.3 Preparation of tablets:

The tablets were prepared by using  bioadhesive polymers in different ratios (A I - Psyllium husk-9%, A II - Sodium carboxymethylcellulose (high viscosity)-6%, A III - carbopal 934-5%, A IV - Sodium alginate-9%, A V -Chitosan-H -9.5%, AVI - Polymethacrylic ethyl acrylate-18%) respectively in different 6 formulations and other excipients were common to all.


Batch code

RST

SST

DF in Tensile tester (N/mm2)

C in (gm) ± S.D

Force

F  (N)

DF  (N/mm2)

C in(gm) ± S.D

Force

F  (N)

DF (N/mm2)

RST  ± S.D

SST  ± S.D

AI

3.860±1.5

37.85

0.189

2.243±1.5

22.00

0.110

0.187±2.5

0.115±3.0

AII

1.018±1.0

9.98

0.050

1.244±1.8

12.20

0.061

0.054±1.8

0.058±1.8

AIII

3.698±1.5

36.27

0.181

2.051±2.0

20.11

0.100

0.179±3.9

0.105±2.6

AIV

1.129±1.0

11.07

0.055

2.196±1.5

21.54

0.108

0.051±2.8

0.102±1.9

AV

0.921±2.0

9.03

0.045

1.954±1.2

19.16

0.096

0.047±4.5

0.098±3.3

AVI

3.425±2.4

33.59

0.168

2.002±1.8

19.63

0.098

0.162±2.2

0.100±1.9

Control

0.243±1.5

2.38

0.012

0.323±2.0

3.17

0.016

0.010±4.8

0.014± 3.2

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 1: Tabulation for measuring detachment force:

n = 3   F - Force = m(mass = C ) X a(acceleration due to gravity- 9.80665 m/s )  RST – Rat stomach tissue      GST – Goat Stomach tissue   C -Weight of required to detach (total drops)    DF - Detachment force    S.D – Standard deviation.

 


 

 

Control tablets containing microcrystalline cellulose instead of bioadhesive polymer were also prepared. The tablets were prepared by wet granulation with PVP K30 as a binder followed by compression in a   Cadmach 8 station compression machine. The surface area of the tablet was found to be 200.29 mm2 ± 5.23 mm2 for all formulations (Mean of 20 tablets ± S.D).

 

3.2. Description of Equipment/Balance: 

In this setup, instead of metal pan, glass beakers with smooth exterior surface, both of exactly same weights were fixed as shown in fig 1.

A – Centre balancing wire

B and C – Left and right side arms holding beaker.

D – Watch glass on water bath stand.

E – Water bath.

F – Stomach tissues (rat and sheep).

G – Bath containing 7.4 pH Phosphate buffer maintained at 37ºC.

F – IV Infusion setup.  

 

Fig no 1: Diagrammatic representation of experimental setup (Modified balance)

 

3.3. Validation of flow rate and drop weight:

After balancing the two beakers, the flow rate of infusion apparatus was validated by measuring the drop speed, drop weight and change of drops weight using distilled water by altering the flow rate. By repeated trials, the flow rate was fixed as 3ml/min. This flow rate was optimal for measurement (for drop weight and drop weight). The average weight of a drop was calculated (20 drops ± S.D).

 

4. Measurement of Bio-Mucoadhesiveness:

The experimental technique is a modification of a previously published method4 Fig 1 shows the arrangement.

The stomach tissue was pasted to the flat watch glass D (facing the air interface) using cyanoacrylate adhesive. The watch glass was fixed with a stand in shaking water bath. This was to maintain the temperature of 37ºC throughout the experiment. The test formulation was fixed to the bottom with adhesive. Weights were added or removed to balance both arms (B and C).                      

 

Fig no 2: Comparison of detachment force measurement in rat stomach tissue by using developed method and (standard) tensile tester.

 

The watch glass with attached tissue (D) was placed such that the stomach tissue was bathed in pH 7.4 Phosphate buffer at a temperature of 37ºC. Then 2 to 3 ml of 0.1 N HCL was spread on mucous layer of stomach to induct the secretion of mucin or mucous ( to mimic in-vivo). A weight of 20 gm was placed on the left side arm (B). This was enable the tablet to come in contact with stomach tissue.

                    

After a contact time of 60 seconds, the weight was removed2. The infusion was started with a constant flow rate of 3ml/min flowing in to (C). The flow was maintained untill the tablet detached from stomach tissue. The bio-mucoadhesive force (N) (or) the detachment force (N/mm2- Force/ Surface area), was determined from the minimal weights that detached the tablet from the stomach tissue2. Fresh stomach tissue pieces were used for each measurement. The accuracy of developed experimental procedure was determined by evaluating bioadhesion of formulations using an universal tensile tester (Lloyd Instruments, LR 50K model, UK). The calculated values shown in Table 1. The comparison of detachment force measurement of developed method with standard tensile tester shown in Fig 2 and 3 respectively.

 

Fig no 3: Comparison of detachment force measurement in sheep stomach      tissue by using developed method and (standard) tensile tester.

 

RESULT AND DISCUSSION:  

Analysis of results obtained in Table 1 shows that calculated detachment force obtained from test procedure not significantly different from the values obtained using universal tensile tester. Students t-test was applied p < 0.01. This shows the accuracy and precision of developed method. Measurements were executed six times and S.D observed in the test was only 4.8. This shows the reproducibility of the evaluation.

 

CONCLUSION:

It was concluded that the developed and validated method is reproducible, accurate and precise. The method was sensitive and can be successfully applied for all tablets containing mucoadhesive polymers.

 

ACKNOWLEDGEMENTS:

The author wishes to acknowledge Mr.P.Siva kumar (pharmaceutics dept) and Mr.G.Manoj (Pharmacology dept) C.L.Baid Metha college of Pharmacy, Chennai for their help and assistance in this work.

 

REFERENCE:

1.      Gu JM, Robinson JR. and Leung SHS. Binding of acrylic polymers to mucin/epithelial surfaces: structure property relationships. CRC Crit Ret, Ther Drug Carrier Systems.1988; 5: 21-67.

2.      Jimenez-Castellanos MR, Zia H and Rhodes CT. Mucoadhesive drug delivery systems. Drug Dev Ind Pharm.1993; 19: 143-194.

3.      Vyas SP and Khar RK. Bioadhesive drug delivery systems. Controlled drug delivery concepts and advances, published by vallabh prakashan. Delhi. 2002; 1st ed: pp. 279 -281.

4.      Hongyi Qi and Wenwen Chen. Development of polaxamer avalogs- based in situ gelling and mucoadhesive pothalmic delivery system for puerarin. Int J pharm. 2007; 337: 178-187.

5.      Choi HG, Oh YK, Kim CK. In situ gelling mucoadhesive liquid suppository containing acetaminophen: enhanced bioavailability. Int J Pharm. 1998; 165: 23-32.

6.      Choi HG, Jung JH, Ryu JM, Yoon SJ, Oh YK. Development of In situ gelling and mucoadhesive acetaminophen liquid suppository. Int J Pharm. 1998; 165: 33-44.

7.      Ch'ng HS, Park H, Kelly P, Robinson JR, Bioadhesive polymers as platforms for oral controlled drug delivery: II. Synthesis and evaluation of some swelling, water-insoluble bioadhesive polymers. J Pharm Sci. 1985; 74: 399-405.

 

 

 

 

Received on 25.02.2009  Modified on 02.03.2009

Accepted on 15.03.2009  © RJPT All right reserved

Research J. Pharm. and Tech.2 (2): April.-June.2009; Page 363-365