You are hereFormulation and In-vitro characterization of Gelatin Micro spheres loaded with Lisinopril dihydrate

Formulation and In-vitro characterization of Gelatin Micro spheres loaded with Lisinopril dihydrate


RESULTS AND DISCUSSION
All the microspheres were prepared by Coacervation Phase Seperation process. Formaldehyde was selected as cross linking agent to prepare the microspheres. This method was selected to formulate the microspheres as because it is quick, easy and cost effective. The composition of all prepared formulations is depicted in Table-1.

                  Table.No.1.Formulation Design of Microparticles

Batch No.

Lisinopril

Dihydrate

(mg)

Gelatin

(gm)

Carbopol

     (gm)

Sodium alginate

(gm)

Formaldehyde

(ml)

F1

20

1

-

-

0.5

F2

20

1.5

-

-

0.5

F3

20

0.75

0.25

-

0.5

F4

20

0.50

0.50

-

0.5

F5

20

0.75

-

0.25

0.5

F6

20

0.50

-

0.50

0.5

Micromeritic Properties of Microspheres
Flow properties of the prepared microspheres were determined by conducting Angle of repose, Bulk density determinations shown inTable No.2,3. Angle of repose of F1, F4& F6 formulations are below 25 and shows excellent flow properties remaining are having good flow properties.The prepared Lisinopril Dihydrate microspheres were subjected to bulk density test and the result indicates good packing property. Among all formulations F6 has shown good micromeritic properties.

Table.No.2 Angle of Repose of Microparticles

S.No

Formulation

Angle of repose

1

F1

25º 40’

2

F2

26º 28’

3

F3

26 º44’

4

F4

24 º48’

5

F5

25º 34’

6

F6

24º 26’

Table.No.3 Bulk Density of Formulations

       Batch no.

Bulk density (gm/ml)

F1

0.55

F2

0.56

F3

0.65

F4

0.46

F5

0.53

F6

0.46

Percentage Yield of Formulations
The percentage yield of microspheres of all the formulations was in the range of 78.90% to 88.53% shown in the Table No.4

Table No.4 Percentage yield of formulations

Formulation


Percentage yield (%)

F1

82.64

F2

78.90

F3

80.95

F4

88.53

F5

80.50

F6

84.16

Drug Entrapment Efficiency of Microspheres
The entrapment efficiency was in the range of 60.78 to 88.24% shown in Table No.5. The formulations F6 and F5 were shown high entrapment efficiency of 83.24% & 82.76% which were made by combination of gelatin and Carbopol polymers.

        Table.No.5  Drug entrapment Efficiency of Microparticles

Formulations

Drug Entrapment Efficiency (%)

F1

60.78

F2

65.30

F3

77.86

F4

80.23

F5

82.76

F6

83.24

Particle size analysis
The mean particle sizes of formulations were in the range of 67.2-76.4 µm. It was mentioned in Table No.6. The mean particle size of optimized formulation was found to be 67.2 µm.

Table.No.6 Mean Particle size of microsphere formulations

S.No

Formulation

Particle size (µm)

1

F1

67.9

2

F2

76.4

3

F3

69.2

4

F4

73.7

5

F5

68.5

6

F6

67.2

Drug Polymer Interaction (FTIR) Study
To check the compatibility of the drug with various polymers, IR spectra of the drug, polymers and combination of the drug and polymers were taken. The IR spectra of the drug and their combinations with polymers are shown in Graph No.1-4. The characteristic major peaks of Lisinopril dihydrate were obtained at 3296.32 cm-1, 3555cm-1, 1658.99cm-1, 1302.02cm-1 and 1420.69cm-1. The values of peaks of drug and its combination with polymers were shown in the Table No.7.It was observed that all the major peaks of Lisinopril dihydrate were intact when it was in combination with polymers and no considerable changes in the IR peaks were observed. So FT-IR spectra indicate the stable nature of Lisinopril in combination with polymers.

Table No.7 Comparision of IR Spectra of Lisinopril dihydrate and in combination with polymers   

S.No.

System

-NH stretch

(cm-1)

-NH2 stretch

(cm-1)

-C=N stretch

(cm-1)

-COOH stretch

(cm-1)

C=C

stretch

(cm-1)

1

Lisinopril dihydrate (LDH)

3296.32

3555.59

1658.99

1343.12

2964.39

2

LDH + Gelatin


3295.51

3556.59

1658.48

1343.11

2964.02

3

LDH + Carbopol


3295.45

3556.48

1658.90

1343.14

2964.15

4

LDH + Sodium alginate

3296.33

3555.16

1658.95

1343.10

2964.10

LDH - Lisinopril dihydrate.

Graph No.1 FT-IR graph of Lisinopril dihydrate (pure drug)

Graph No.2 FT-IR graph of Lisinopril dihydrate + Gelatin

Graph No.3 FT-IR graph of Lisinopril dihydrate+ Gelatin +carbopol

Graph No.4 FT-IR graph of Lisinopril dihydrate+ Gelatin +sodium alginate

Morphological Examination
Morphology of the microspheres was investigated by scanning electron microscopy. The photograph of formulation F6 taken by scanning electron microscope was shown in the Figure No.1. The microspheres were spherical in shape and free flowing.

Figure No.1 SEM of Formulation F6 under Low Magnification

In vitroDrug Release Studies
Dissolution profile of gelatin containing Lisinopril dihydrate Microspheres in Phosphate buffer pH 7.4 showed that Micro spheres with low amount of gelatin released 85.0% (F1) of Lisinopril after 18 hrs while Micro spheres prepared with high amount of gelatin released only 79.4% (F2) of Lisinopril. The dissolution profiles of all formulations upto 18 hrs  were shown in the Table No.8. The In-vitro Dissolution profile of gelatin-carbopol containing Lisinopril dihydrate Microspheres in Phosphate buffer pH 7.4 showed that Microspheres with high amount of carbopol were most effective in slowing down the drug release 82.5% (F4), while the Micro spheres containing high amount of sodium alginate were released 72.1% (F6) of Lisinopril for 18 hrs at controlled rate. Comparative dissolution of all 6 formulations were sown in Figure No.2. So F6 was taken as optimized formulation for its high entrapment efficiency and controlled release.

Table.No.8 Comparative cumulative percentage release profile of                                                 formulations   F1-F6

Time

(hrs)

Cumulative percentage drug release (%)

F1

F2

F3

F4

F5

F6

2

11.3

13.8

11.3

9.2

12.1

14.7

4

25

21.3

20

26

21.8

27.4

6

50.5

40.8

45

46.3

38.1

33.8

8

57.3

55.7

60.8

53.7

49.7

46.5

10

63.4

62.3

63.1

60.5

       55.9

54.9

12

69.1

68.2

66.7

66.3

60.7

65

14

74.2

71.8

69.3

71.4

65.3

66.3

16

79.7

75.9

70.5

76.8

70.5

69.2

18

85

79.4

72.8

82.5

75.2

72.1

Fig.No.2 Comparative dissolution profile of formulations

kinetic studies         
The data obtained from the in-vitro dissolution studies was subjected for kinetic treatment to obtain the order of release and best fit model for the formulations.              
The data obtained in the in-vitro dissolution studies were grouped in to modes of data treatments as follows:
*Cumulative percent drug release v/s time (Zero order).
* Cumulative percent drug release v/s square root of time (Higuchi Matrix Model).
* Log cumulative percent drug retained v/s time (first order).
*Log cumulative percent drug release v/s log time (krosmeyer peppas model).

The results of the in vitro dissolution studies of formulations F1 to F6 are shown in Table No.8. The plots of cumulative percentage drug release v/s time, log cumulative percentage drug retained v/s time and cumulative percent drug release v/s square root of time, log cumulative percent drug release v/s log time were drawn and represented graphically. All the formulations exhibited anomalous non-fickian diffusion (n value is in between 0.5 to 1.0) mechanism and it was shown in the TableNo.9. The drug release mechanism was diffusion controlled as the plot of higuchi model is linear. The kinetic graphs of F6 formulation are shown in the Graph No.5-8.

Table No.9 Kinetic Release Data of Formulations

Formulations

Zero order plots

First order plots

Higuchi plots

Korsmeyer-peppas plot

Possible drug release mechanism

R2

R2

R2

R2

n

F1

0.9618

0.9899

0.9908

0.9836

0.5892

Non-fickian, higuchi

F2

0.9136

0.8885

0.9701

0.9801

0.5962

Non-fickian, higuchi, first order.

F3

0.9604

0.9913

0.9882

0.9882

0.5847

Non-fickian, first order, higuchi.

F4

0.9414

0.9774

0.9768

0.9849

0.5834

Non-fickian, higuchi, first order.

F5

0.9666

0.8539

0.9950

0.9877

0.5728

Non-fickian, higuchi, first order.

F6

0.9416

0.9018

0.9782

0.9948

0.5475

Non-fickian, higuchi, zero order.

ACCELERATED STABILITY STUDIES
Stability study was carried out for the formulations F1 and F5 at 37°C ± 1°C & 60°C for a period of 45 daysand the results were noted in Table No.10. The decrease in the percentage yield of formulations F1 and F5 were less, after 45 days of stability studies and they were considered as stable products

Table No.10 Stability Studies of Percentage Drug Content of Formulation F1 & F5

Days

F1

F5

37?C&65%RH

60?C

37?C&65%RH

60?C

1

60.74

60.70

83.20

83.09

7

59.57

58.23

82.12

81.98

14

56.29

55.03

81.09

80.02

21

55.09

54.18

80.45

79.23

38

54.13

53.21

78.97

78.54

45

52.06

50.98

77.05

76.37

Conclusion
The Micro encapsulation of Lisinopril Dihydrate  with gelatin,  gelatin –carbopol and gelatin-Sodium alginate by co-acervation phase separation technique utilizing temperature change and cross linking with formaldehyde, was able to sustain the drug release efficacy. The microspheres having gelatine-sodium alginate and gelatin-carbopol polymers mixtures (F6&F3) provides the best sustained release formulations and other formulations (F1, F2) may be suitable for prolonged action formulations. These studies compared the release behaviour of gelatin, gelatin-sodium alginate and gelatin –carbopol controlled release system of Lisinopril microspheres. The F3 & F6 formulations had more pronounced controlled release effects compared with other formulations and F6 formulation is considered as optimised formulation among all formulations.

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