FABRICATION AND CHARACTERIZATION OF GASTRORETENTIVE DRUG …

www.wjpps.com Vol 6, Issue 7, 2017.

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Sahu et al. World Journal of Pharmacy and Pharmaceutical Sciences

FABRICATION AND CHARACTERIZATION OF

GASTRORETENTIVE DRUG DELIVERY SYSTEM BASED IN

SUPERPOROUS HYDROGEL COMPOSITE

Aakash Sahu* and Abha Doshi

MET Institute of Pharmacy MET Complex, Bandra Reclamation, Bandra (West), Mumbai

400050, India.

ABSTRACT

Superporous hydrogels (SPHs) were originally developed as a novel

drug delivery system to retain drugs in the gastric medium. These

systems instantly swell in the stomach and maintain their integrity in

the harsh stomach environment while releasing the pharmaceutical

active ingredient. Superporous hydrogel composite (SPHC) have more

porosity and more mechanical strength compared to SPH. In the

present work, the main aim was to develop, evaluate and optimize

superporous hydrogel composite of Zinc carnosine. Acrylamide and

acrylic acid are the monomers used for the synthesis of ZnC-SPHCs.

The prepared ZnC- SPHCs were evaluated for different physical

properties and other evaluation parameters viz; equilibrium swelling ratio, equilibrium

swelling time, density, porosity, void fraction, gelation kinetics, swelling reversibility studies,

total floating time, drug content; in vitro release. All the evaluation parameters were found to

be within acceptable limits. The ZnC-SPHC showed sustained release for a period of 8 h

thereby achieving therapeutic efficacy and good patient compliance. Optimization of formula

was done by selecting 23 full factorial designs. It was employed to study the effect of

independent variables of (X1)-amount of BIS, (X2)-amount of Ac-Di-Sol, (X3)-amount of

Sodium bicarbonate, which significantly influenced the dependent variables % cumulative

release (drug release), swelling ratio and swelling time (min). The optimized ZnC-SPHC

were found to be stable when exposed to accelerated stability conditions.

KEYWORDS: Zinc carnosine (ZnC), Superporous hydrogel composite (SPHC),

Optimization, RP-HPLC.

WORLD JOURNAL OF PHARMACY AND PHARMACEUTICAL SCIENCES

SJIF Impact Factor 6.647

Volume 6, Issue 7, 575-600 Research Article ISSN 2278 – 4357

Article Received on

24 April 2017,

Revised on 14 May 2017,

Accepted on 03 June 2017

DOI:10.20959/wjpps20177-8038

*Corresponding Author’

Aakash Sahu

MET Institute of Pharmacy

MET Complex, Bandra

Reclamation, Bandra (West),

Mumbai 400050, India.


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INTRODUCTION

Oral dosage forms have really progressed from immediate release to delayed release to

sustained release and site-specific delivery as well. Conventional oral dosage forms such as

tablets, capsules provide specific drug concentration in systemic circulation without offering

any control over drug delivery and also cause great fluctuations in plasma drug levels which

may lead to therapeutic ineffectiveness of the administered drug or may produce undesirable

toxicity and side effects. Oral sustained release drug delivery systems provide drug release at

a predetermined, predictable and controlled rate.[1, 2]

Dosage forms that can be retained in the

stomach are called gastroretentive drug delivery systems (GRDDS).[3]

GRDDS can improve

the controlled delivery of drugs that have an absorption window by continuously releasing

the drug for a prolonged period of time before it reaches its absorption site.

Superporous hydrogels (SPHs) were originally developed as a novel drug delivery system to

retain drugs in the gastric medium. These systems should instantly swell in the stomach and

maintain their integrity in the harsh stomach environment, while releasing the pharmaceutical

active ingredient. SPHCs swell in shorter period and increase in size manifold as it is

superporous even after swelling its density remains lower than gastric fluid and so it floats in

the stomach for longer period of time and releases drug slowly over the period of time. Zinc-

carnosine is an artificially produced derivative of carnosine in which a zinc ion and carnosine

are bound in a 1:1 ratio to create a chelate compound. It has been used for gastritis, gastric

ulcers, and dyspepsia symptoms. It appears that the combination chelate is 3 times more

effective than each individual ingredient alone.[4]

Zinc carnosine is unique as it supports the natural cytoprotective mechanism without

interfering in natural digestive process. For its antiulcer activity it should be retained in

stomach for longer period and so we have developed gastro retentive drug delivery system of

zinc carnosine by using superporous hydrogel composite (SPHCs). Zinc carnosine unique

transport capabilities are thought to be dependent upon its ability to remain in the gastric

juice without immediately being destroyed. By prolonging its existence, zinc carnosine is

able to maintain tissue-supportive effects for a long period of time.

MATERIALS AND METHODS

Zinc carnosine was received as a gift sample from Puneet Laboratories Pvt. Ltd. (Mumbai,

India). Acrylamide, Acrylic acid , N, N'-Methylenebisacrylamide, Ammonium persulfate ,

N, N, N', N'-Tetramethylethylenediamine, Cross carmillose sodium [Ac-Di-Sol], Span 80,


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Sodium bicarbonate, 1-Decane sulfonic salt HPLC grade, Acetonitrile HPLC grade,

Isopropyl alcohol, Methanol HPLC grade, Potassium bromide AR grade was obtained from

SD Fine Chemicals Ltd. (Mumbai, India).

Name of Ingredients Role of each ingredient

Zinc carnosine Active ingredient

Acrylamide Monomer

Acrylic acid Monomer

BIS Cross linking agent

Span 80 Foam stabilizer

APS Polymerization initiator pair

TEMED Catalyst

Ac-Di-Sol Composite agents

Sodium bi-carbonate Gas generating agents

METHOD

A) Formulations made by using BIS and Ac-Di-Sol

Table .1: Trial formulations of ZnC-SPHCs F1 to F7.

Ingredients Formulation Code

F1 F2 F3 F4 F5 F6 F7

Zinc carnosine (mg) 75 75 75 75 75 75 75

Acrylamide (µl) 300 300 300 300 300 300 300

Acrylic acid (µl) 200 200 200 200 200 200 200

BIS (µl) 50 70 90 110 130 150 170

Span-80 (µl) 50 50 50 50 50 50 50

APS (µl) 50 50 50 50 50 50 50

TEMED (µl) 20 20 20 20 20 20 20

Ac-Di-Sol (mg) 30 40 45 50 55 60 65

Sodium bi-carbonate

(mg) 150 150 150 150 150 150 150

Table.2: Trial formulations of ZnC-SPHCs F8 to F13.


F8 F9 F10 F11 F12 F13

Zinc carnosine

(mg) 75 75 75 75 75 75

Acrylamide

(µl) 300 300 300 300 300 300

Acrylic acid

(µl) 200 200 200 200 200 200

BIS

(µl) 190 210 230 250 270 290

Span-80

(µl) 50 50 50 50 50 50

APS 50 50 50 50 50 50


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(µl)

TEMED

(µl) 20 20 20 20 20 20

Ac-Di-Sol

(mg) 70 75 80 85 90 95

Sodium bi-carbonate

(mg) 150 150 150 150 150 150

Synthesis of SPHCs using gas blowing technique[2]

Various trial batches of ZnC-SPHCs were synthesized using different amount of BIS (μl) and

Ac-Di-Sol (mg) as both these variables affect the swelling properties and porosity which

should be in harmony to yield porous hydrogels. The various amounts of BIS and Ac-Di-Sol

were selected on the basis of literature survey. The addition of composite agent (i.e. Ac-Di-

Sol) did not affect the foaming and polymerization. The different amounts (30 – 95 mg) of

Ac-Di-Sol and (50 – 290 µl) of BIS were tried to evaluate the effect on swelling studies,

density and porosity. At 50 to110 µl of BIS and 30 to 50 mg of Ac-Di-Sol non-

uniform/porous ZnC-SPHCs were obtained which might be due to decreased viscosity and

porosity which hindered the process of simultaneous crosslinking and porogenation. At 230

to 290 µl of BIS and 80 to 95 mg of Ac-Di-Sol uniform/highly porous ZnC-SPHCs were

obtained which might be due to increased viscosity and porosity which hindered the process

of simultaneous crosslinking and porogenation. Therefore ZnC-SPHCs containing 130 and

210 µl BIS and 55 to 75 mg Ac-Di-Sol, uniform & porous ZnC-SPHCs were obtained and

were used for further studies. Final composition of various ZnC-SPHCs formulations is

depicted in Table 1 and Table 2.

Fourier Transform Infrared (FT-IR) Studies

FT-IR spectra of pure Zinc carnosine and excipients were taken to assure the compatibility

between the two. Infrared spectrum was taken (Shimadzu FT-IR system, Japan) by scanning

the samples in KBr discs.

EVALUATION OF Znc-SPHC

The prepared ZnC-SPHCs were evaluated for different physical properties like equilibrium

swelling time, equilibrium swelling ratio, density, porosity, scanning electron microscopy

analysis, gelation kinetics, void fraction, swelling reversibility studies, water retention and

other evaluation parameters like drug content, in vitro release study.


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a) Equilibrium swelling ratio

Swelling experiments were conducted in double distilled water (DDW) and 0.1N HCl.

Cylindrical shape hydrogel samples were weighed and measured in diameter and length.

Samples were immersed into double distilled water (DDW) and 0.1N HCl at room

temperature. At predetermined time intervals, each sample was taken out of the water to

measure the weight, diameter and length of the swollen sample using balance and an

electronic digital caliper.[3]

The equilibrium swelling ratios were calculated based on those

measured data.

The Equilibrium swelling ratio (Qv) is defined as per equation (1).

Q = (Ms – Md) / Md …………………………… (1)

Where Ms is the Mass of the swollen hydrogel and Md is the Mass of the dried hydrogel.

b) Equilibrium swelling time

Equilibrium swelling time was calculated by immersing the ZnC-SPHCs in deionized water

and 0.1N HCl calculating the time required to attain equilibration in swelling.[3]

c) Density

For density measurement, the solvent displacement method was used. Dried ZnC-SPHCs,

which were treated with different solvents, were used for density measurements, which

actually show the apparent densities of SPHCs. Pieces of ZnC-SPHCs were taken and

weighed in order to determine the mass of each piece. A hydrophobic solvent such as hexane

that is not absorbed by SPHCs was used for this purpose. By the use of forceps, a piece of the

polymer was immersed in a predetermined volume of hexane in a graduated cylinder and the

increase in the hexane volume was measured as the volume of the polymer.

The density was calculated from the following equation (2).

Density (D) = M SPHC / V SPHC………………………………….... (2)

Where V SPHC is the volume of SPH displaced by solvent and M SPHC is the mass of

SPHC.[3]

d) Porosity

For porosity measurement, dried ZnC-SPHCs were immersed in hexane overnight and

weighed after excess hexane on the surface was blotted [60]. The porosity was calculated

from the following equation (3).


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Porosity = V P / V T……………………………………………….. (3)

Where V T is the total volume of SPH and V P= V T - V SPH, is the pore volume of SPHC.

Total volume of SPHC can be measured from its dimensions as it is cylindrical in shape.[12]

e) Void fraction

The void fraction inside super porous hydrogels (ZnC-SPHCs) was determined by immersing

the hydrogels in HCl solution (pH 1.2) up to equilibrium swelling. By using these data, the

dimensions of the swollen hydrogels, sample volumes were determined. The difference

between the weight of the swollen hydrogel and the weight of dried hydrogel gives the

amount of buffer absorbed into the hydrogels and it indicates the total volume of pores in the

hydrogels.[13]

The void fraction was calculated by the following equation.

Void Fraction = Dimensional volume of the hydrogel / Total volume of pores …….. (4)

f) Determination of gelation kinetics

As gelation (polymerization reaction) proceeded, the viscosity of the mixture continuously

increased until the full network (gel) structure was formed. Gelation time was defined as the

duration of gel formation and was measured by a simple tilting method after adjustment of

pH to 5.0 with acetic acid. This parameter was taken as the time taken until the reactant

mixture was no longer descending in the tilted tube position.[5]

g) Swelling reversibility studies

Pulsatile pH-dependent swelling of the superporous hydrogels (ZnC-SPHCs) was evaluated

by alternation of the swelling medium between the 0.1N HCl solution (pH 1.2) and phosphate

buffered solution (PBS, pH 7.4). The hydrogels were first swollen in pH 1.2 HCl solutions

for 30 min. The swollen hydrogels in the HCl solution were weighed at each given time and

transferred to the phosphate buffer solution. The same procedures were performed for

swelling in PBS before transferring the swollen hydrogels back to the HCl solution. The

hydrogels were transferred to the alternating solutions every 30 min.[6]

h) Water Retention

For determination of the water-retention capacity of the ZnC-SPHCs as a function of the time

of exposure at 37ºC, the water loss of the fully swollen polymer at timed intervals was

determined by gravimetry.[6]


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The following equation is used to determine the water retention capacity (WRt) as a function

of time.

WRt = (Wp - Wd) / (Ws - Wd) …………………………..………….. (5)

Where, Wd is the weight of the dried hydrogel, Ws is the weight of the fully swollen

hydrogel, and Wp is the weight of the hydrogel at various exposure times.

i) Drug content uniformity

20 dosages of ZnC-SPHCs were taken and each were weighed and dissolved in 100 ml water:

0.1N HCl (80:20) using sonicator. The solution was filtered and after suitable dilution

analyzed for drug zinc carnosine in HPLC at 215 nm. The experiments were carried out in

triplicate for the drug loaded SPHC of all the formulations and average values were

recorded.[7, 8]

j) Drug loading

Drug loading was carried out in all SPHC composition (SPHCs containing 75 mg zinc

carnosine). Drug (75mg) mixed with Ac-Di-Sol was directly added into reaction mixture

before addition of sodium bicarbonate. The SPHC samples were dried completely in 24 h.

k) In vitro floating time

The in vitro floating behavior of the ZnC-SPHCs was determined by floating time. The ZnC-

SPHC was placed in USP Type II dissolution apparatus containing 900 ml of 0.1N HCl with

50 rpm at 37±0.50C. Total floating time was determined.

l) In vitro drug release

In vitro release of drug from ZnC-SPHCs was evaluated in triplicate at 37±0.5ºC using the

United State Pharmacopoeia (USP) dissolution test apparatus type I (Basket method) at a

rotation speed of 50 rpm in 900 ml 0.1N HCl (pH 1.2) for 8 h. At regular time intervals, 2 ml

of the dissolution medium was withdrawn, replaced with an equivalent volume of the fresh

dissolution fluid and analyzed for the drug using the HPLC at 215 nm.

m) Mechanism of release

The mechanism of release was determined by fitting the obtained release data to the various

kinetic equations such as zero-order, first-order, Higuchi matrix and Korsmeyer-Peppas

models.[9, 10]

The best-fit model was selected by comparing the R2 values of the release

profile corresponding to each model depicted in table 12.


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n) Stability studies

ZnC-SPHC of the optimized formulation was tested for stability under two conditions for a

period of three months. All the ZnC-SPHC were kept in air tight glass containers and stored

in stability chambers maintained at 40ºC/75% RH and room temperature. Formulation was

evaluated for their physical parameter like appearance and other parameters equilibrium

swelling ratio, equilibrium swelling time, density, porosity, void fraction, in vitro drug

release and content of active ingredient at the end of 30 days, 60 days and 90 days of storage

period.

Parameter like equilibrium swelling ratio, equilibrium swelling time, density, porosity, void

fraction, in vitro drug release and content of active ingredient was determined.

RESULTS AND DISCUSSION

EVALUATION

The various evaluation tests were carried out on ZnC-SPHCs of 400 mg. All the observations

represent the mean ± S.D. (standard deviation) and n = 20 for drug content uniformity and n

= 3 for others.


The swelling ratio of all formulations in 0.1N HCl solution are represented in Table 3 and

Fig. 1. The swelling ratio of the prepared formulations in 0.1N HCl solution was found to

increase with time. Swelling was also found to be dependent on concentration of BIS and Ac-

Di-Sol. The swelling ratio of ZnC-SPHCs decreases by increasing the cross-linking density

and porosity, as tighter networks were formed at higher concentration of cross-linking agents

and composite agent. As tighter networks were formed as the pores are closed by composite

agent, reducing the flexibility of polymeric chains retarding their swelling. The BIS and Ac-

Di-Sol concentration was effective at optimum concentration in the solution mixture.

Optimum crosslinking and porosity results in uniform and porous ZnC-SPHCs which resulted

in better swelling properties.

Equilibrium swelling ratio was observed in all the prepared trial formulations.


The equilibrium swelling time of the ZnC-SPHCs varied. The slow swelling in F1 to F6 is

due to lower amount of BIS and Ac-Di-Sol. This might be due to decrease in crosslinking and


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porosity. This results in hardening and rigidity of polymer network which contributes to

maintenance of capillary channels. The fast swelling in F7 to F13 is due to higher amount of

BIS and Ac-Di-Sol. This might be due to increase in crosslinking and porosity. This results in

highly porous and crossliking SPH of polymer network which contributes to maintenance of

capillary channels. The addition of composite agent reduces the time for equilibrium swelling

as observed in ZnC-SPHC. The reason may be again that physical crosslinking by composite

agent to primary polymeric network maintains the capillary channels of hydrogel which

provide easy absorption of solvent, thereby reduces the swelling time. Increase in composite

agent however did not further affect the equilibrium swelling time as observed for F1 to F13

in table 3 and fig 1.

Table 3: Equilibrium swelling time of trial formulations F1-F13.

Formulation Time (min) Swelling ratio (Q)

F1 30 ± 2 330.26 ± 0.0105

F2 30 ± 1 342.01 ± 0.0115

F3 35 ± 2 337.54 ± 0.079

F4 35 ± 2 339.47 ± 0.001

F5 30 ± 2 335.43 ± 0.016

F6 30 ± 1 300.6 ± 0.0045

F7 20 ± 2 350.26 ± 0.001

F8 25 ± 2 331.92 ± 0.001

F9 20 ± 3 268.42 ± 0.001

F10 20 ± 2 252.01 ± 0.0065

F11 20 ± 2 293.42 ± 0.0087

F12 25 ± 2 239.73 ± 0.032

F13 25 ± 2 229.47 ± 0.0143

Fig 1: Equilibrium swelling time of trial formulations F1-F13.


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c) Density

The apparent densities of the various ZnC-SPHCs ranged between 0.050 ± 0.057 g/cm3. ZnC-

SPHCs have density lower than that of the swelling media, DDW and SGF and so all float on

the swelling medium. Since the hydrogels are very porous, the measured density is related to

the porosity of the polymer and can be defined as apparent density. The actual density of the

polymer is the same but when the polymer has many pores, the occupied volume will be

more, thus resulting in low apparent density. Table 4 shows density of all trial formulation.

d) Porosity

ZnC-SPHCs showed porosities ranging from 86.29 ± 2.1% to 93.73 ± 0.90%. High porosity

values suggest the formation of superpores which were formed due to addition of Ac-Di-Sol,

BIS and most importantly sodium bicarbonate. SEM images support the formation of

interconnected pores and capillary channels. A higher concentration of BIS produces a larger

degree of polymer chains branching and generates an additional network. Thereby, with the

BIS content increasing, the crosslinking density increases. Table 4 shows porosity of all trial

formulation.

e) Void fraction

There is directed correlation of density and porosity with the void fraction. Formulation F5-

F8 was showing more void fraction compared to other formulation. The increase in void

volume led to an increase in the amount of uptake of water into the structure, resulting in

increase in the swelling ratio (vice versa). Table 4 shows void fraction of all trial formulation.

Table 4: Density, porosity, void fraction of trial formulations F1-F13.

Formulation Density (gm/cc) Porosity

(%)

Void

fraction

F1 0.057 ± 0.057 91.26279 7.7

F2 0.052 ± 0.0577 90.29199 6.1

F3 0.0572 ± 0.057 88.92274 6.3

F4 0.0537 ± 0.057 91.26279 6.2

F5 0.0506 ± 0.0577 93.73335 10.4

F6 0.0546 ± 0.057 91.54463 11.8

F7 0.0572 ± 0.057 89.75035 12.8

F8 0.0574 ± 0.057 91.26279 9.6

F9 0.0538 ± 0.057 92.92286 8.5

F10 0.0574 ± 0.057 93.2513 5.7

F11 0.057 ± 0.057 93.44709 7.5

F12 0.057 ± 0.057 90.29199 8.7

F13 0.0572 ± 0.057 89.51535 8.5


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f) Gelation kinetics

The gelation kinetics gives good information for determining the introduction time of

blowing agent (sodium bicarbonate). The most salient property of a superporous hydrogel is

its fast swelling ability, because of the presence of large and uniform pores within the

polymer structure which are produced due to the formation of foam at the time of

polymerization. In order to produce large and uniform pores, the blowing agent must be

introduced when the reactants have appropriate viscosity. Bubbles cannot maintain their

shape for a long time if a gas blowing agent is added too early or if gelation time is relatively

longer. On the other hand, bubbles cannot even be formed if porogen is introduced too late or

the gelation time is extremely short because, the reaction system becomes viscous at such a

short period that the added porogen cannot produce bubbles. The foaming reaction took place

only under the acidic condition (pH 5.0–5.2). The polymerization proceeded rapidly and the

gelling usually started within 30 sec. Hence sodium bicarbonate was introduced 30 seconds

after the addition of APS and TEMED.

Table 5 shows the gelation kinetics of ZnC-SPHCs.

Table 5: Gelation kinetics of trial formulations F1-F13.

Formulation Time in sec

F1 35 ± 3

F2 35 ± 2

F3 30 ± 4

F4 30 ± 3

F5 33 ± 4

F6 33 ± 3

F7 32 ± 4

F8 34 ± 5

F9 35 ± 6

F10 34 ± 4

F11 33 ± 4

F12 34 ± 3

F13 34 ± 4

g) Swelling reversibility studies

Fig. 2 shows the swelling reversibility of the ZnC-SPHC between pH 1.2 and pH 7.4

solutions. The structure of the superporous hydrogel composite with large numbers of pores

connected to one another to form capillary channels was favorable for easy diffusion of the

swelling medium into the polymeric matrix, thus contributing to its quick response toward pH

change. It was observed that ZnC-SPHCs at pH 1.2 have particular swelling capacity. As pH


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was changed from 1.2 to 7.4, there was considerable increase in swelling of ZnC-SPHCs.

Again when pH was decreased, there was deswelling of the polymer, which was shown as

decrease in swelling ratio. (F6, F7, F8 and F9 is selected batches).

Fig 2: Swelling reversibility studies of trial formulations F6-F9.

h) Water Retention capacity (degradation kinetics)

WRt was calculated by using equation (3). Fig 3 shows the degradation kinetics of ZnC-

SPHCs. Lower the concentration of crosslinking agent in the hydrogel, faster and greater is

the water loss. Higher concentration of crosslinking agent and composite a chain support

water retention.

Wd = wt. of dried SPH

Ws = wt. of SPH at swollen state

Wp = wt. of SPH at various exposure time

Fig. 3: Water Retention of trial formulations F1-F13.


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The drug content was observed to be high and uniform in all the formulations and was

observed in the range 97.35-99.21%.

Table 6: Drug content of trial formulations F1-F13.

Formulation Drug content (%) Formulation Drug content (%)

F1 98.41 ± 0.36 F8 98.96 ± 0.18

F2 98.88 ± 0.24 F9 97.35 ± 0.41

F3 98.64 ± 0.13 F10 99.21 ± 0.21

F4 99.11 ± 0.07 F11 98.33 ± 0.20

F5 98.41 ± 0.07 F12 98.12 ± 0.15

F6 99.47 ± 0.29 F13 99.21± 0.06

F7 99.05 ± 0.12

j) Drug loading

75 mg zinc carnosine was used for drug loading in ZnC-SPHCs formulations. F1- F13 was

successfully prepared by direct addition of drug. The dried ZnC-SPHCs were very light

weight and have porous networks. Hexane dehydration was carried out as it takes less time

for drying.

k) In vitro floating time

All the formulations floated for more than 24 hrs. in 0.1 N HCl (pH 1.2). It shows ZnC-SPHC

have required density which is due to superporous nature of the polymer.

l) In vitro release study

The release profile of Znc-SPHC shows release of the extended period of time. Fig. 4 give the

corresponding drug release at that particular time interval for the different trial formulations.

Fig 4: In vitro release profiles at 50 rpm (Basket) of trial formulations F1-F13.


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1. F1 and F2

Formulation F1 contains BIS 50µl and Ac-Di-Sol 30mg, whereas F2 contains BIS 70µl and

Ac-Di-Sol 40mg. Both the formulations showed good equilibrium swelling ratio but they

were taking more time (30min.) for swelling compared to F7-F13 formulations. Dissolution

rate studies were performed for 8 h which showed 68% drug release for F1 and 85.2% for F2.

2. F3 and F4

Formulation F3 contains BIS 90µl and Ac-Di-Sol 45mg, whereas F4 has BIS 110µl and Ac-

Di-Sol 50mg. Both the formulations showed good equilibrium swelling ratio but they were

taking more time (30min.) for swelling compared to F7-F13 formulations. Dissolution rate

studies were performed for 8 h which showed 83.8 % drug release for F3 and 85.2% for F4.

3. F5 and F6


Di-Sol 60mg both the formulations showed good equilibrium swelling ratio but they were

taking more time (30min.) for swelling compared to F7-F13 formulations. Dissolution rate

studies were performed for 8 h which showed 82.5% drug release for F5 and 82.7% for F6.

4. F7 and F8

Formulation F7 contains BIS 170 µl and Ac-Di-Sol 65 mg, whereas F8 has BIS 190µl and

Ac-Di-Sol 70mg. Both the formulations showed good equilibrium swelling ratio and less

time was taken to swell. Dissolution rate studies were performed for 8 h which showed 86.6

% drug release for F7 and 79.5% for F8.

5. F9 and F10


Di-Sol 80mg. Both the formulations showed good equilibrium swelling ratio and less time

was taken to swell. Dissolution rate studies were performed for 8 h which showed 78.5%

drug release for F9 and 83.1% for F10.

6. F11 and F12

Formulation F11 contains BIS 230µl and Ac-Di-Sol 85mg, whereas F13 has BIS 250µl and

Ac-Di-Sol 90mg. Both the formulations showed good equilibrium swelling ratio and less

time was taken to swell. Dissolution rate studies were performed for 8 h which showed

86.4% drug release for F11 and 79.5% for F12.


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F13

Formulation F13 contains BIS 270µl and Ac-Di-Sol 95mg. The formulations showed good

equilibrium swelling ratio and less time was taken to swell. Dissolution rate study was

performed for 8 h which showed 79.5% drug release.

The F7 formulations of ZnC-SPHC showed sustain release profile and drug release was

found to be 86.6%. It was showing maximum equilibrium swelling ratio, porosity, void

fraction and was taking less time for swelling amongst all formulations. Therefore

formulation F7 was selected for optimization.

Selection of batch for optimization study by Design Expert Stat Ease Software.

F7 containing BIS 170µl and Ac-Di-Sol 65mg showed desired equilibrium swelling ratio in

minimum time, steady and uniform dissolution profile for 8 h. Main objective was to

optimize batch considering (+1) high level, (-1) low level of three independent variables and

study outcome of dependent variables.

OPTIMIZATION OF FORMULATION

Formulation F7 from the trial formulations was considered for optimization using 23

full

factorial design. The three factors were evaluated; each at 3 levels and experimental trials

were performed on all 8 possible combinations by using Stat-Ease Design Expert software

8.0.7.1 trial version. The amounts, (X1)-amount of BIS, (X2)-amount of Ac-Di-Sol, (X3)-

amount of Sodium bicarbonate, were selected as independent variables as shown in Table 7.

The responses % cumulative release (drug release), swelling ratio and swelling time (min)

were selected as dependent variables.

Table 7: Amount of variables in formulations by 23 factorial design.

Levels Factors - Actual values

X1(µl) X2(mg) X3(mg)

1 180 67.5 160

-1 160 62.5 140

Where X1-amount of BIS, X2-amount of Ac-Di-Sol, X3 -amount of Sodium bicarbonate,

(+1) high level of X1, X2 & X3, (-1) low level of X1, X2, & X3.

a) Fourier Transform Infrared (FT-IR) Studies

FT-IR spectra of pure Zinc carnosine and excipients


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Fig. 5: FT-IR spectra of zinc carnosine.

Fig. 6: FT-IR spectra of Zinc carnosine, Acrylamide and BIS.

Table 8: Optimized formulations of Zinc carnosine.


B1 B2 B3 B4 B5 B6 B7 B8

Zinc carnosine

(mg) 75 75 75 75 75 75 75 75

Acrylamide

(µl) 300 300 300 300 300 300 300 300

Acrylic acid

(µl) 200 200 200 200 200 200 200 200

BIS

(µl) 180 180 180 160 160 160 160 180

Span-80 50 50 50 50 50 50 50 50


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(µl)

APS

(µl) 50 50 50 50 50 50 50 50

TEMED

(µl) 20 20 20 20 20 20 20 20

Ac-Di-Sol

(mg) 62.5 67.5 62.5 62.5 67.5 67.5 62.5 67.5

Sodium bi-carbonate

(mg) 140 140 160 160 140 160 140 160


Fig. 7 shows the equilibrium swelling ratio of the optimized formulations. Optimized

formulations B1-B8 started to swell within a minute when kept in gastric fluid. The swelling

ratio increased with increase in concentrations of BIS and Ac-Di-Sol in formulation. The

equilibrium swelling ratio of the formulations was observed for a period of 30 min.


Optimized formulations B1-B8 started to swell within a minute when kept in gastric fluid.

The rate of swelling increased with increase in concentrations of sodium bicarbonate and

there was no effect of BIS and Ac-Di-Sol on swelling time while increasing the amount. The

swelling time of the formulations were observed for a period of 30 min and B2 showed

maximum swelling ratio and minimum swelling time of formulation. The equilibrium

swelling time of the formulations were determined for a period of 30 min as shown in Fig 7.

Fig 7: Equilibrium swelling time of optimized formulations.


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c) Density

The apparent densities of the optimized ZnC-SPHCs ranged between 0.060 ± 0.069 g/cm3,

indicating higher the concentration of BIS lower was the density.

d) Porosity

Table 9 shows the porosity of the optimized formulations. ZnC-SPHCs showed porosities

ranging from 87.41± 0.4% to 93.56 ± 0.2%, reflecting the increase in porosity with increase

in the concentration of Ac-Di-Sol and BIS, which was due to increase in number of pores..

e) Void fraction

Table 9 shows the void fraction of the optimized formulations. Among all the formulations,

B2 showed higher void fraction.

Table 9: Density, porosity and void fraction of optimized formulations.

Formulation Density

(gm/cc)

Porosity

(%)

Void

fraction

B1 0.063 93.56 6.8

B2 0.060 92.92 12.3

B3 0.062 92.29 9.6

B4 0.069 89.32 11.2

B5 0.066 87.41 7.5

B6 0.068 90.29 7.7

B7 0.066 89.85 6

B8 0.061 93.56 5

f) Determination of gelation kinetics

Table 10 shows the gelation time of the optimized formulations. The foaming reaction takes

place only under the acidic condition and therefore the pH was adjusted between 5.0-5.2. The

polymerization reaction is very fast and so the gelling usually started within 30 sec, hence

sodium bicarbonate was introduced 30 seconds after the addition of polymerization initiator

APS and polymerization catalyst TEMED.

Table 10: Gelation time for optimized formulations.

Formulation Time in sec

B1 30 ± 2

B2 30 ± 3

B3 32 ± 4

B4 34 ± 5

B5 30 ± 4

B6 33 ± 3


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B7 28 ± 2

B8 34 ± 4

g) Swelling reversibility studies (degradation kinetics)

Fig 8 shows the swelling reversibility of the optimized formulations. All formulation have

less swelling ratio in 0.1N HCl.

Fig. 8: Swelling reversibility of optimized formulations in 0.1N HCl and PBS.

h) In vitro floating time

All the formulations floated for more than 24 hrs. in 0.1 N HCl (pH 1.2). It shows ZnC-SPHC

have required density which is due to superporous nature of the polymer.


The drug content was observed to be high and uniform in all the formulations and was

observed in the range 97.15-98.71% (table 11).

Table 11: Drug content of trial formulations B1-B8

Formulation Drug content (%) Formulation Drug content (%)

B1 98.33 ± 0.13 B5 98.64 ± 0.42

B2 98.26 ± 0.73 B6 98.21 ± 0.83

B3 97.15 ± 0.13 B7 98.71 ± 0.12

B4 98.65 ± 0.6 B8 98.54 ± 0.34


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j) Scanning electron microscopy analysis

The scanning electron microscopic image of SPH composite shows presence of pores in the

prepared SPH composite (Fig.9). Also it can be noticed in the image that the pores are

connected to each other to form extensive capillary channels, which help the dried gels to

swell to near equilibrium size in a matter of minutes.

Fig 9: Scanning electron microscopic image of optimized B2 ZnC-SPHC.

k) In vitro release study in 0.1 N HCl

The release rate of ZnC-SPHCs was determined using USP Type I Apparatus. The drug

release test was performed using 900 ml of 0.1N HCl, at 37 ± 0.5˚C at 50 rpm for 8 h. A 5 ml

sample was withdrawn from the dissolution apparatus at specified time points and the

samples were replaced with fresh dissolution medium. The samples were filtered through a

0.45 µm membrane filter and 2ml of above solution diluted with water to 10 ml and drug

concentration was measured by HPLC. Percentage cumulative drug release of B1-B8 is

shown in Fig 10.

The in vitro drug release profiles of the formulations for optimization in 0.1 N HCl is shown

in Fig 10. The in vitro drug release studies were performed for 8 hours and steady release

patterns were observed in all the formulations. The optimized formulation B2 showed the

highest release 88.6 %. It is observed that the release of drug increases with the increase in

concentration of BIS. This could be explained by the ability of hydrophilic polymers to

absorb water, thereby promoting dissolution and hence the release of the drug.


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Fig. 10: In -vitro release profiles of formulations B1-B8 for optimization in 0.1 N HCl.

l) Kinetic analysis of in vitro release data.

Table 12 gives the release mechanisms of the formulations B1-B8 for optimization. The

interpretation of release kinetics data was based on the value of the resulting coefficients of

determination. The release kinetics of zinc carnosine followed first order. To understand the

mechanism of release of ZnC from the SPHC; the drug release data was fitted into

Korsmeyer-Peppas and Higuchi model and it showed the highest R2 value for Korsmeyer-

Peppas model, closely followed by Higuchi model, indicating diffusion to be predominantly

by the non-Fickian type as the ‘n’ values lies between 0.45-0.89.

Table no 12: Kinetic analysis of in vitro drug release data of optimized formulations

Formulation

code

Zero

order

First

order

Higuchi

model

Hixen

crowell

Korsmeyer-

Peppas Best fit model

(R2) (R

2) (R

2) (R

2) (R

2) n

B1 0.6644 0.8436 0.8444 0.1445 0.9433 0.2596 Korsmeyer-Peppas



B4 0.5619 0.7204 0.7637 0.1919 0.9148 0.2232 Korsemeyers- peppas


B6 0.8108 0.9265 0.9578 0.6289 0.9175 0.4336 Higuchi model

B7 0.8179 0.9203 0.9467 0.7552 0.9183 0.5519 Higuchi model

B8 0.8750 0.9258 0.9356 0.6676 0.9328 0.3703 Higuchi model


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m) Surface response and Contour plots.

Fig 11: Surface response plot for % cumulative drug release.

Fig 12: Contour plot depicting % cumulative drug release.


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Fig 13: Surface response plot for equlibrium swelling ratio.

Fig 14: Contour plot depicting equlibrium swelling ratio.


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Fig 15: Surface response plot for equlibrium swelling time.

Fig 16: Contour plot depicting equlibrium swelling time.


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Fig 17: Overlay plot of optimized formulation.

n) Stability studies

Table 13: Stability study results of optimized formulation B2 at room temp. and 40°C

Physical Parameter Condition 0 day 30th

day 60th

day 90th

day

Appearance 40ºC/75% RH ++ ++ ++ ++

RT ++ ++ ++ ++

Equilibrium swelling

ratio

40ºC/75% RH 219 ± 0.02 210 ± 0.05 205 ±0.3 187 ±0.7

RT 219 ± 0.02 218 ± 0.04 200± 0.04 177± 0.04

Equilibrium swelling time

(min)

40ºC/75% RH 10 10 10 10

RT 10 10 10 10

Density (gm/cc) 40ºC/75% RH 0.060 0.060 0.057 0.072

RT 0.060 0.060 0.052 0.078

Porosity (%) 40ºC/75% RH 92.92 92.71 92.44 86.5

RT 92.92 92.70 92.57 84.8

% Drug content 40ºC/75% RH 98.26 97.96 97.40 92.5

RT 98.26 97.77 97.34 91.7

CONCLUSION

It may be concluded that ZnC-SPHC would be a promising drug delivery system for

administration of Zinc carnosine (ZnC). The studies reveal that the drug can be successfully

delivered via the specific site. The ZnC-SPHC were of matrix type giving sustained release

and were prepared by gas blowing method by direct addition of drug. The hydrophilic

polymers showed good swelling characteristics. The statistical approach for optimization of

formula is a useful tool, particularly when two or more variables are to be evaluated


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simultaneously. The results of optimization studies showed that formulation containing 180

µl of BIS, 67.5 mg of Ac-Di-Sol and 140 mg of sodium bicarbonate were the most acceptable

formulation and proved as a satisfactory carrier for gastroretentive drug delivery of zinc

carnosine. The optimized formulation showed good swelling ratio and sustained drug release

for 8 h.

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