Formulation and evaluation of antidiabetic mucoadhesive microspheres

Vishal Gupta¹, Navneet Garud¹, Rajendra Chauhan¹, Hemant Mourya¹,

Pawan Kushwah¹, Ramakant Joshi²*

¹School of Studies in Pharmaceutical Sciences, Jiwaji University, Gwalior, 474011, India.

²Amity Institute of Pharmacy, Amity University Madhya Pradesh, Gwalior, 474005, India.

*Corresponding Author E-mail: joshiram78@gmail.com

ABSTRACT:

The present investigation was aimed to prepare alginate-acacia microspheres by ionic cross-linking method or Ionotropic gelation method. Systematic preformulation study performed as per the standard procedure as described for the identification and authentication of drug sample. Calibration curve was prepared as spectrum of this solution was recorded in 200-400 nm range using U.V. spectrophotometer. FT-IR spectrum of standard drug was done by FT-IR from 400-4000cm^-1 by using potassium bromide. Total 8 formulations (F1-F8) were prepared. The microsphere of Vildagliptin was preparedusing ionotropic gelation system also exhibited the smallest particle size of 176.65 micrometres. Formulation F4 exhibited the highest percentage entrapment efficiency of 78.85% with the highest percentage of mucoadhesion (70.23%). Formulation F4 has a zeta potential of -36.45 mV. A zeta potential with a magnitude above 30 mV (either positive or negative) typically indicates good stability in colloidal systems. The optimized formulation of the Vildagliptin loaded acacia-sodium alginate microspheres was tested after 3 months of storage at room temperature.

KEYWORDS: Microspheres, Gastrointestinal tract, Mucoadhesive, Diabetic, Vildagliptin.

INTRODUCTION: 

Microspheres are small, sphere shaped particles generally fabricated using biocompatible and biodegradable polymers having 1 to 1000 μm size rangand incorporating drugs and other bioactive within their core¹. They proposevarious advantages e.g. protecting and masking the drugs in it from the unkind GIT environment, sustained and controlled drug release, improved stability, and bioavailability, site-specific targeting of the active therapeutic moieties, etc^2,3.

Vildagliptin is prescribed in the treatment of type II diabetes mellitus in adults⁴. It is indicated as dual therapy together with metformin, a sulphonylurea, or a thiazolidinedione in adult’s patients with insufficient glycemic control regardless of maximal tolerated dose of monotherapy⁵. Vildagliptin half-life is 3 hours. Its initial dose is 50mg twice daily.

Due to its less half-life it is necessary to develop a sustained/controlled release preparation⁶. Therefore, it would be advantageous to develop a sustained release formulation which remains at the absorption site for an extended timeperiod. Several approaches have been proposed to prolong the gastric residence time of formulation at absorption site and one of these is the development of oral controlled release bioadhesive system⁷.

The present investigation was aimed to prepare alginate- acacia microspheres by ionic cross- linking method or Ionotropic gelation method. The water based ionic cross-linking technique can provide distinctivebenefit over conventional microsphere methods which involve “all-aqueous” systems that avoidremaining solvents in microspheres⁸.

Table No. 1: Formulation of mucoadhesive microsphere of Vildagliptin

Ingredients	F1	F2	F3	F4	F5	F6	F7	F8
Vildagliptin (mg)	50	50	50	50	50	50	50	50
Sod. alginate (mg)	1000	1000	1000	1000	1000	1000	1000	1000
Acacia Nilotica (mg)	500	750	1000	1250	1500	1750	2000	2250
CaCl2 (%)	5	5	5	5	5	5	5	5
Distilled water  (ml)	30	30	30	30	30	30	30	30

MATERIALS AND METHOD:

Materials:

Vildagliptin as gift sample was provided by Century Pharmaceuticals Ltd. Vadodara, Gujarat. Sodium alginate was gifted sample from CDH (New Delhi); Acacia was obtained as a gift sample from Sardana gums and chemicals industries. All other chemicals used were of analyticalgrade and were used without additional purification.

Method of Microspheres Formulation:

The microspheres of Vildagliptin wereprepared utilizing ionotropic gelation system. Right off the bat, in this strategy essential quantity of A. nilotica gum and sodium alginate was measured⁹. Taken ingredients were blended using distilled water with the help of stirrer for 1 h and required quantity of Vildagliptin was measured and mixedwell ceaselessly in above blend and for 3 h^10-11. Resultant mixture was pushed outdrop wise with help of syringe and needle into 50 ml of calcium chloride solution at 50 rpm. After 60 min prepared microspheres were washed with distilled water and at dried at 50°C for 6h, prepared18 clumps of microspheres were stored in desiccators. Expanding the convergence of A. nilotica gum and keeping the grouping of sodium alginate and Vildagliptin consistent¹².

Mucoadhesive Test:

The in vitro mucoadhesion study of prepared microspheres was evaluated by established falling liquid film technique. Goat’snasal mucosa strip was kept on a glass slide and 25 mg of microspheres were scattered on it. This glass slide was incubated for 15 minute to allow the polymer to interact with the membrane and finally placed at an angle of 45°. Phosphate buffer saline pH 6.4 was allowed to flow over the membrane at the rate of 1 ml/min for 5 min with the help of a burette. The effluent was collected on a watch glass. At the end of this process, the detached particles collected, were dried and weighed the mucoadhesion was also found to be dependent on the surface area of particle. As the particle surface area increased, the mucoadhesion was also found to be increased as shown in Table¹³.

In vitro drug release in gastrointestinal fluids:

The prepared microspheres were evaluated for in vitro drug release at standard conditions. 0.1 N HCl (900 ml) was used as dissolution medium. The drug release of mucoadhesive microsphere was calculated with the help of UV Vis. Spectroscopy¹⁴.

RESULTS AND DISCUSSION:

Preformulation Study:

Organoleptic properties like color, nature, odor and taste have been performed on the obtained gift sample of drug sample found compiles with reported properties. The melting point showed as 152^ºC and Vildagliptin is easily soluble in DMF (di methyl formamide), methanol and 0.1M HCl, moderately soluble in ethanol and acetonitrile, soluble in water and 0.1M NaOH¹⁵.

Fig 1: UV Spectra of Pure Drug (Vildagliptin)

Infrared Spectroscopy:

The FT-IR spectra of SA polysaccharide show similar bands as shown in the literature. The bond corresponding to O-H stretching vibrations appears around 3307. CH₂ stretching is depicted at wavenumber 2928 cm^-1. The bands corresponding to symmetric C-O stretching vibrations of the carboxylate group appears at 1590 cm^-1 and 1411 cm^-1. Other vibrations like 1075 cm^-1 attributed to the C-H aliphatic stretching vibrations.
In compatibility test FT-IR spectra all the three ingredients found to be compatible with each other and do not show any kind of interaction. Drug and polymers show their individual peaks as NH stretching bond of Vildagliptin at 3294 cm^-1.

Fig. 2: FT-IR spectra of Drug-Polymer mixture

Table No. 2: Results of Percentage Yield Evaluation of Vildagliptin Microspheres

Formulation Code	Percentage Yield*	Percentage Entrapment Efficiency*	Mean particle size*	Percentage Mucoadhesion
F1	68.85±0.15	65.58±0.25	189.32±2.65	65.12
F2	63.32±0.25	70.23±0.36	210.85±3.68	64.65
F3	71.15±0.30	71.65±0.15	236.65±2.15	61.14
F4	76.65±0.10	78.85±0.22	176.65±2.36	70.23
F5	69.98±0.18	69.98±0.16	198.85±4.85	62.23
F6	63.32±0.32	66.65±0.32	245.65±3.98	68.85
F7	64.65±0.19	68.78±0.15	230.14±2.15	61.15
F8	67.52±0.22	65.23±0.18	228.85±3.25	64.95

*Average of three determinations (n=3)

Differential Scanning Calorimetry:

The thermogram of raw vildagliptin raw material exhibited the typical profile of a pure, crystalline drug (melting endothermic peak at 148^ºC) thermogram of unprocessed sodium alginate is characterized by a wide endothermic peak at 70^ºC and an exothermic peak at 250^ºC. The endothermic peak of sodium alginate may be caused by the loss of water and moisture content of the polysaccharide, and the exothermic peak corresponds to its thermal decomposition.

Fig. 3: DSC thermogram of Drug Polymer Mixture

Formulation of Vildagliptin Mucoadhesive Microspheres:

Fig. 4: Formulation of Vildagliptin Mucoadhesive Microspheres

Percentage Yield: 

Formulation F4 demonstrated the highest percentage yield of 76.65 ± 0.10%. This suggests that the production process for F4 was efficient, resulting in a relatively high yield of Vildagliptin microspheres. Formulation F3 also showed a substantial percentage yield of 71.15 ± 0.30%, indicating that the manufacturing process for F3 was efficient in producing a significant amount of microspheres¹⁶.

Mean Particle Size:

Formulation F4 exhibited the smallest mean particle size of 176.65 micrometres. Smaller particle sizes are often desirable for drug delivery systems as they can provide a larger surface area for drug release and potentially faster dissolution. Formulation F1 also had a relatively small mean particle size of 189.32 micrometres, which is advantageous for drug delivery. Formulation F5 and F2 had mean particle sizes of 198.85 and 210.85 micrometres, respectively, falling within an acceptable range for microspheres¹⁷.

Fig. 5: Mean particle size of formulations

Drug Entrapment Efficiency (DDE):

Formulation F4 exhibited the highest percentage entrapment efficiency of 78.85%. This suggests that F4 was highly effective in encapsulating Vildagliptin within the microspheres, making it a promising formulation for controlled drug release. Formulation F3 also showed a substantial entrapment efficiency of 71.65%, indicating efficient drug encapsulation within the microspheres.

Fig. 6: % Entrapment efficiency of formulations

Percentage of Mucoadhesion:

Formulation F4 stands out with the highest percentage of mucoadhesion (70.23%). This suggests that it has a strong ability to adhere to mucous membranes, potentially providing extended contact with the absorption site and enhanced drug absorption. Formulation F6 also shows relatively high mucoadhesion (68.85%), indicating strong adhesion properties.

Fig. 7: Mucoadhesion properties of formulations

Determination of zeta potential:

Formulation F4 has a zeta potential of -36.45 mV. A zeta potential with a magnitude above 30 mV (either positive or negative) typically indicates good stability in colloidal systems. In this case, the negative zeta potential suggests that the microspheres in F4 have a net negative charge on their surface, which can help prevent particle aggregation and improve stability in suspension.

In-vitro drug release studies:

Fig. 8: Cumulative percentage drug release of formulations

Stability Studies:

The optimized formulation of the Vildagliptin loaded acacia-sodium alginate microspheres was tested after 3 months of storage at room temperature. The stability test indicates no significant change in the appearance, vildagliptin content and dissolution microspheres. Therefore, these studies demonstrate excellent stability results over the period of months¹⁸.

CONCLUSION:

The work demonstrates the successful development and optimization of the Vildagliptin loaded sodium alginate-acacia microspheres. The formulation is based on linear sodium alginate and highly branched acacia gum using ionotropic gelation method for the controlled oral drug delivery system. The advantage of the formulation includes availability of polymers, low cost, reproducibility and easily controlled method for fabrication. A DSC study shows that there was no any chemical interaction between drug and polymers whereas all the materials show their identical peaks. Mean particle size analysis indicates microspheres are of specialized size and drug is properly dispersed within the polymeric matrix. Increase in polymer concentration leads to slight decrease in percentage yield increase in drug entrapment efficiency, particle size and degree of swelling, while in vitro release and mucoadhesivity of microspheres are pH dependant. Possible molecular interactions in the optimized matrix microspheres are identified using FTIR analysis which confirms the chemical stability of the drug molecule in the formulation. The stable structure of the optimized Vildagliptin loaded sodium alginate and acacia microspheres results in high drug entrapment efficiency and good stress relaxation properties controlled by a pH-dependant swelling behaviour.

CONFLICT OF INTEREST:

The authors have no conflicts of interest regarding this investigation.

ACKNOWLEDGMENTS:

The authors would like to thank SCAN Research Laboratory, Bhopal for their kind support during evaluation and all other lab studies.

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Received on 15.12.2023      Revised on 06.05.2024

Accepted on 09.08.2024   Published on 24.12.2024

Available online from December 27, 2024

Research J. Pharmacy and Technology. 2024;17(12):5944-5948.

DOI: 10.52711/0974-360X.2024.00901

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