Probiotics - based Dosage form Development against H. Pylori
induced Gastric Disorders

 

Shubham Gautam, Rimpy, Jaishree Sharma, Deepak Ranga, Surender Verma*

Institute of Pharmaceutical Sciences, Kurukshetra University, Kurukshetra - 136119 (Haryana), India.

*Corresponding Author E-mail: svpharma.kuk@gmail.com

 

ABSTRACT:

Background: Helicobacter pylori (H. pylori) infection is a major cause of gastric ulcers and gastric cancer. Conventional antibiotic therapy often faces limitations due to resistance and side effects. Probiotics such as Lactobacillus acidophilus can improve gastric health and enhance therapeutic efficacy. The present study aimed to develop and optimize an esomeprazole–probiotic mucoadhesive microsphere formulation for gastric delivery.

Materials and Methods: Mucoadhesive microspheres were prepared using sodium alginate and Carbopol 934 by the ionic gelation method, with calcium chloride as the crosslinking agent. A Box–Behnken design was employed to optimize key formulation variables (polymer concentration and stirring speed) with entrapment efficiency, particle size, and yield as responses. The formulations were characterized for entrapment efficiency, probiotic survival in simulated gastric fluid (pH 2), swelling index, mucoadhesion on rat gastric mucosa, FTIR compatibility, SEM morphology, and in vitro drug release kinetics. Results: The optimized formulations (OM1 and OM2) demonstrated high entrapment efficiency (>94%), strong mucoadhesive strength, and excellent probiotic stability in acidic gastric conditions. FTIR confirmed drug–polymer compatibility, and SEM revealed spherical porous microspheres. In vitro release studies showed sustained drug release over 12h, following zero-order and Korsmeyer–Peppas kinetics. Conclusion: Esomeprazole–probiotic microspheres exhibited significant probiotic protection, controlled drug release, and good gastric mucoadhesion, indicating their potential as a promising alternative strategy for the management of H. pylori–induced gastric disorders.

 

KEYWORDS: Helicobacter pylori, probiotics, esomeprazole, mucoadhesive microspheres, controlled release, sodium alginate, Carbopol 934.

 

 


1.    INTRODUCTION:

Helicobacter pylori (H. pylori) is a Gram-negative, spiral-shaped, microaerophilic bacterium infecting the gastric mucosa and implicated in chronic gastritis, peptic ulcer disease, mucosa-associated lymphoid tissue (MALT) lymphoma, and gastric carcinoma.

 

Systematic reviews show its global adult prevalence declined from approximately 52.6% before 1990 to 43.9% during 2015–2022, though rates remain elevated among adolescents (around 35.1%)ą. Current eradication therapies rely on proton pump inhibitors (PPIs) combined with antibiotics; however, increasing antimicrobial resistance, treatment side effects, and frequent relapse reduce long-term success rates1,2.

 

Probiotic supplementation has emerged as a promising adjunct therapy. An umbrella meta-analysis of 534 randomized trials reported that probiotics improved eradication rates (RR ≈ 1.10) and halved the risk of side effects (RR ≈ 0.54). Furthermore, meta-analyses incorporating Limosilactobacillus reuteri or Saccharomyces boulardii demonstrated significant improvements in eradication efficacy and notable reductions in adverse events3,4.   

Multiparticulate mucoadhesive microspheres offer targeted gastric delivery, prolong residence time, improve release kinetics, and protect encapsulated agents. Sodium alginate–based systems, often augmented with Carbopol 934, are widely used for their biocompatibility, mucoadhesive properties, and ability to shield acid-labile components such as PPIs and probiotics5.

 

Optimization of such formulations through Quality by Design (QbD), particularly using Box–Behnken response surface methodology, is well supported in pharmaceutical research. This approach enables systematic fine-tuning of variables such as polymer concentration, stirring speed, and crosslinker ratios to maximize entrapment efficiency, particle size control, and manufacturability6.

 

Despite these advances, few studies have co-encapsulated a PPI (e.g., esomeprazole) together with live probiotics in a mucoadhesive microsphere while also applying systematic optimization and evaluating probiotic survival, mucoadhesion, and release performance. This study addresses that gap by developing and optimizing such a formulation to enhance H. pylori treatment outcomes7.

 

2. MATERIALS AND METHODS:

2.1 Chemicals and reagents:

Esomeprazole was kindly provided by Torrent Pharmaceuticals (Baddi, Himachal Pradesh, India). Lactobacillus acidophilus culture was obtained from the Department of Pharmaceutical Sciences, Kurukshetra University, Kurukshetra. Carbopol 934P was purchased from Loba Chemie Pvt. Ltd. (Mumbai, India), and sodium alginate was obtained from Kurukshetra University. Calcium chloride and other analytical-grade reagents were procured from HiMedia Laboratories (Mumbai, India). All chemicals and reagents used were of analytical grade and were utilized without further purification.

 

2.2 Preparation of Microspheres:

Mucoadhesive microspheres containing esomeprazole and Lactobacillus acidophilus were prepared using the ionic gelation technique. Sodium alginate and Carbopol 934 were dissolved in distilled water under constant stirring to obtain a homogeneous polymeric solution. Esomeprazole and probiotic cultures were dispersed into the polymeric solution under gentle stirring to ensure uniform distribution8.

 

The resulting dispersion was extruded dropwise through a 26 G syringe, from a distance of approximately 3 cm, into a gently stirred calcium chloride solution (cross-linking agent). Microspheres were allowed to cure in the solution for 30 min to ensure complete crosslinking. The formed microspheres were collected by filtration, washed thoroughly with sodium chloride solution to remove unbound drug and probiotics, and finally dried at room temperature.

 

2.3 Experimental Design for Optimization (Box–Behnken):

A Box–Behnken design (BBD), a three-factor, three-level statistical design, was employed to optimize the formulation variables. The independent variables selected were:

A: Concentration of sodium alginate (% w/v)

B: Concentration of Carbopol 934 (% w/v)

C: Stirring speed (rpm)

 

The dependent variables (responses) were:

Y1: Entrapment efficiency (%EE)

Y2: Particle size (µm)

Y3: Practical yield (%)

 

Each factor was studied at three levels (low −1, medium 0, high +1). Experimental design and statistical analysis were performed using Design-Expert® software (Version 11, Stat-Ease Inc., USA). Response surface plots and contour plots were generated to visualize the influence of independent variables, while numerical optimization was applied to identify the most desirable formulation.

 

2.4 Calibration Curve Preparation (UV–Vis):

Stock 1 (1000µg/mL): Dissolve accurately 5mg esomeprazole in 5mL of 0.1 N HCl in a volumetric flask.

Stock 2 (100µg/mL): Dilute 1mL of Stock 1 to 10mL with 0.1 N HCl.

·       Working standards: Prepare 5, 10, 15, 20, and 25 µg/mL by appropriate dilution of Stock 2 with 0.1 N HCl.

·       Measurement: Record absorbance at λ_max = 282 nm using a UV–Vis spectrophotometer (200–400 nm range; 10 mm quartz cuvette) against reagent blank.

·       Linearity: Plot absorbance vs concentration and obtain the regression equation for subsequent quantification.

 

2.5 Solubility Studies (Esomeprazole):

Evaluate qualitative solubility/dispersion of esomeprazole in water, methanol, simulated gastric fluid (SGF, pH 1.2), and phosphate buffer (pH 6.8). For each medium, add excess drug, shake at ambient temperature, allow to equilibrate, and assess clarity/dispersion.

 

2.6 Melting Point Determination:

Determine the melting point of esomeprazole magnesium by capillary method using a calibrated melting point apparatus. Report onset and completion temperatures9.

2.7 Drug–Excipient Compatibility (FTIR):

Record FTIR spectra of esomeprazole, L. acidophilus (lyophilized), sodium alginate, Carbopol 934P, and physical mixtures (drug+excipients) using KBr pellet method (Bruker Alpha; 4000–400 cm⁻ą; 4 cm⁻ą resolution; standard scan speed). Examine spectra for characteristic peaks and potential shifts/vanishing bands suggesting interactions.

 

2.8 Morphological Characterization (SEM):

Mount dried microspheres on aluminum stubs with double-sided tape, sputter-coat with gold under vacuum, and image by scanning electron microscopy at suitable magnifications. Record surface features (shape, porosity) for representative batches.

 

2.9 Flow Properties of Microspheres:

Evaluate bulk density (BD) and tapped density (TD) using standard funnels and tap-testers. Compute:

·       Carr’s index, CI (%) = [(TD − BD)/TD] × 100

·       Hausner ratio, HR = TD/BD

·       Angle of repose (fixed-funnel method): θ = arctan (h/r), where h = heap height, r = radius. Perform each measurement in triplicate.

 

2.10 Probiotic Encapsulation Efficiency (%EE, cells):

1.     Accurately weigh an aliquot of microspheres and lyse in phosphate buffer (pH 7.4) with gentle agitation to release entrapped cells.

2.     Perform serial dilutions and plate on MRS agar.

3.     Incubate plates at 37±0.5°C for 48 h; count CFU.

4.     Calculate: %EE (cells) = (N_e/N_t) × 100, where N_t is the initial viable count added and N_e is viable cells recovered post-encapsulation. Conduct in triplicate.

 

2.11 Stability of Encapsulated Probiotics in SGF (Acid Tolerance):

Incubate microspheres in SGF (pH 2.0) containing pepsin (3.0g/L) at 37±0.5°C. At predetermined time points, retrieve samples, neutralize, lyse, plate on MRS agar, and enumerate CFU after incubation (37°C, 48h). Express survival relative to initial count. Include free-cell controls where applicable.

 

2.12 Swelling Index (pH 1.2):

Immerse pre-weighed dried microspheres (W₀) in 0.1 N HCl (pH 1.2) at 37±0.5°C. At set intervals, remove, gently blot surface, and weigh (W_t). Compute: Swelling Index (%) = [(W_t − W₀) / W₀] × 100. Report the mean of triplicates.

 

2.13 In Vitro Mucoadhesion Test:

Use freshly excised rat gastric mucosa (ethical approval/biowaste compliance as applicable). Mount mucosa on the basket of a USP disintegration apparatus. Place a known quantity of microspheres on the mucosal surface, then subject to sequential dipping in SGF (37 °C) for a defined period/number of dips. Quantify adhered vs detached microspheres by recovery/weighing or counting. % Mucoadhesion = (Adhered/Initial) × 100.

 

2.14 In Vitro Drug Release (Dissolution):

Conduct dissolution using USP Apparatus II (paddle) with 900mL 0.1 N HCl (pH 1.2) at 37±0.5°C, 50rpm. Withdraw 5mL aliquots at predetermined intervals up to 12h, immediately filter, and analyze at 282nm using the calibration curve. Replace withdrawn volume with fresh medium maintained at 37°C to preserve sink conditions. Perform in triplicate.

 

2.15 Drug Release Kinetics (Modeling):

Fit release data to:

·       Zero-order: Qt=k0tQ_t = k_0 tQt​=k0​t

·       Higuchi: Qt=kHtQ_t = k_H \sqrt{t}Qt​=kH​t​

·       Korsmeyer–Peppas: Mt/M∞=ktnM_t/M_\infty = k t^nMt​/M∞​=ktn (fit first ~60% release; log–log transform to obtain n). Compute correlation coefficients (R˛) and compare goodness-of-fit. Interpret n (sphere geometry): ~0.43 (Fickian), 0.43–0.85 (anomalous), ~0.85 (case-II).

 

2.16 Short-Term Stability of Microspheres:

Store representative batches at ambient laboratory conditions (24–28°C) for 30 days in closed containers protected from light. Evaluate physical appearance, particle size distribution, mucoadhesion, drug content, probiotic viability, and FTIR profile at baseline and end-study, following the same methods as above.

 

2.17 ANOVA and Model Adequacy (Design-Expert):

Analyze BBD datasets by ANOVA (α = 0.05) to assess model significance and factor effects, including linear, interaction, and quadratic terms. Evaluate lack-of-fit, residual diagnostics (normal probability plots, studentized residuals), and model adequacy metrics (R˛, adjusted R˛, predicted R˛, Adequate Precision). Apply Box-Cox transformation if required to stabilize variance and improve normality.

 

2.18 Response Surface Mapping and Overlay Plot:

Generate 3D response surface and 2D contour plots to visualize factor interactions on Y1–Y3 while holding one factor constant. Conduct numerical and graphical optimization; produce an overlay plot with constraints to identify the design space and select optimal formulations for confirmatory runs.

 

3. RESULTS AND DISCUSSION:

3.1 Optimization Results of Microspheres (OM1 and OM2):

The Box–Behnken design generated 17 experimental runs with varied concentrations of sodium alginate, Carbopol 934P, and stirring speed. The observed responses included entrapment efficiency, particle size, and practical yield. Statistical analysis revealed that polymer concentration and stirring speed significantly influenced microsphere characteristics.

Formulations R3 and R9 exhibited superior performance with high entrapment efficiency, favorable particle size, and acceptable yield.


 

Table 1. Optimization parameters for microsphere formulations

Std

Run

Factor 1

Factor 2

Factor 3

Response 1 (Y1)

Response 2 (Y2)

Response 3 (Y3)

A: Polymer Sodium Alginate

B: Polymer Carbopol934

C: Stirring Speed

Entrapment efficiency

Particle size

Practical Yield

%

%

RPM

%

(µm)

%

9

1

2

1

1000

85

0.9435

85

15

2

2

1.5

1250

75

0.844

79

10

3

2

2

1000

90

0.578

87

5

4

1

1.5

1000

69

1.22

70

14

5

2

1.5

1250

87

0.855

87

13

6

2

1.5

1250

76

0.92

82

4

7

3

2

1250

78

1.4705

71

12

8

2

2

1500

88

1.017

75

11

9

2

1

1500

85

0.9812

87

6

10

3

1.5

1000

71

0.9456

75

7

11

1

1.5

1500

77

0.7012

61

1

12

1

1

1250

80

1.15

73

2

13

3

1

1250

79

1.97

89

16

14

2

1.5

1250

71

0.81

77

3

15

1

2

1250

83

1.024

82

17

16

2

1.5

1250

78

0.8002

87

8

17

3

1.5

1500

61

2.25

73

 


Based on desirability functions, these were selected as optimized formulations and renamed as OM1(R3) and OM2(R9). Both formulations demonstrated robust manufacturing reproducibility and were carried forward for detailed characterization.

 

3.2 Calibration Curve of Esomeprazole:

The calibration curve of esomeprazole in 0.1 N HCl (λ_max = 282nm) showed a strong linear relationship between concentration (5–25µg/mL) and absorbance. The regression equation (y = mx + c) indicated excellent correlation (R˛ > 0.99), confirming the suitability of this method for accurate drug quantification during release studies.

 

Figure 1. Calibration Curve graph for Esomeprazole

 

 

 

Table 2. Prepration of Calibration curve

S. No

Conc. (µg/ml)

Absorbance

1

0

0

2

5

0.146

3

10

0.304

4

15

0.462

5

20

0.617

6

25

0.753

 

3.3 Solubility Studies:

Esomeprazole exhibited good aqueous solubility and was freely soluble in methanol, simulated gastric fluid (pH 1.2), and phosphate buffer (pH 6.8). These findings confirm its suitability for gastric-targeted delivery. The probiotic L. acidophilus showed good viability in aqueous and acidic conditions, supporting its stability in gastric formulations when properly encapsulated.

 

Table  3. Solubility Studies

Sr. No.

Solvents

Lactobacillus acidophilus

1.

Water

++

2.

Methanol

+++

3.

pH 1.2

+++

4.

pH 6.8

+++

Freely soluble =+++, Soluble= ++

 

3.4 Melting Point Determination:

The melting point of esomeprazole magnesium was found to be 153°C, in agreement with literature values. This consistency confirmed the purity and identity of the drug used for microsphere preparation.

 

 

 

.

3.5 FTIR Analysis (Drug–Excipient Compatibility):

FTIR spectra of esomeprazole, excipients, and physical mixtures exhibited the characteristic peaks of each component without significant shifts or disappearance. Key absorption bands of esomeprazole, such as the C=O stretching and N–H bending vibrations, remained intact. Similarly, alginate and Carbopol peaks were well preserved in the mixtures. These findings suggest the absence of any major chemical interaction between drug, excipients, and probiotics, confirming compatibility of the formulation components.

The FTIR spectra of the physical mixtures showed the characteristic peaks of esomeprazole and excipients without significant peak shifts or disappearance, suggesting the absence of chemical interactions (Figures 2–5).


 

Figure 2. IR spectra of the drug (Esomeprazole)

 

Figure 3. IR spectra of Probiotics

 

Figure 4. IR spectra of composition of drug, Probiotics and other excipients

Figure 5. FT-IR spectra of optimized formulation (OM1)


Figure 6. SEM results shows (a) perforated microsphere with surface morphology (b) Surface of Microspheres varying in size, (c) Pores in microspheres.

 

3.6 Scanning Electron Microscopy (SEM) Analysis:

SEM micrographs of the optimized microspheres revealed well-formed, spherical particles with a relatively smooth external surface. At higher magnifications, pores were observed on the surface, which may facilitate controlled drug release by enabling diffusion pathways. The uniform spherical shape indicated efficient ionic gelation, while the porous morphology was attributed to the polymer blend of sodium alginate and Carbopol 934P. These morphological features are desirable for gastro-retentive systems, as they enhance both mucoadhesion and sustained release behavior.

 

 

 

3.7 Flow Properties of Microspheres:

The flowability of microspheres was evaluated using standard pharmacopeial parameters. Both OM1 and OM2 exhibited good flow, with bulk density and tapped density values leading to low Carr’s indices (3–4%) and Hausner’s ratios close to 1.1. The angle of repose values (22–26°) fell within the range of excellent flowability. These findings suggest that the microspheres can be handled and processed easily during large-scale manufacturing without risk of aggregation or poor flow.

 

Table 4.  Flow properties of microspheres

Formulation code

Bulk density

(g/cm3)

Tapped density

(g/cm3)

Carr’s index (%)

Hausner’s ratio

Angle of repose

OM1

0.89

0.98

4.0

1.19

26.57

OM2

0.82

0.92

3.1

1.14

22.17

 

3.8 Probiotic Encapsulation Efficiency:

Encapsulation efficiency for L. acidophilus was found to be high, with OM1 achieving 95.56% and OM2 achieving 94.6%. Such high values confirm the effectiveness of the alginate–Carbopol matrix in entrapping viable probiotic cells. Efficient encapsulation is critical for ensuring that probiotics survive the harsh gastric environment and are delivered intact to the site of action.

 

Table 5. Probiotics encapsulation efficiency of OM1 and OM2.

Formulation Code

Probiotic Encapsulation efficiency

OM1

95.56%

OM2

94.6%

 

3.9 Stability of Encapsulated Probiotics in Simulated Gastric Fluid (SGF):

When exposed to SGF (pH 2.0 with pepsin), free probiotics showed rapid loss of viability, whereas encapsulated cells retained significant stability. After incubation, OM1 demonstrated a survival rate of 73.9%, while OM2 retained 79% of viable cells. This confirms that the mucoadhesive microspheres provided effective protection against acidic degradation, thus ensuring probiotic delivery to the gastric mucosa where H. pylori resides.

3.10 Swelling Index Studies:

Swelling behavior of microspheres in acidic medium (pH 1.2) was time-dependent, with OM1 exhibiting higher swelling compared to OM2. After 5 hours, OM1 showed a swelling index of approximately 40%, while OM2 reached 34%. The greater swelling observed in OM1 is likely due to the higher proportion of Carbopol 934P, which absorbs water and undergoes matrix expansion. This enhanced swelling contributes to prolonged gastric residence time and stronger mucoadhesion, ultimately improving localized drug delivery.

 

Table 6. Swelling index of selected Optimized formulations

Time (hours)

OM1

OM2

0.5

2

1.9

1

4.8

3.5

2

11

6.3

3

14.5

12.5

4

31.58

19

5

40

34.28

 

3.11 In Vitro Mucoadhesion Test:

The mucoadhesion study using excised rat gastric mucosa demonstrated that both optimized microsphere formulations adhered strongly to the gastric lining. OM1 showed superior mucoadhesion (76.36%) compared to OM2 (67.27%). The higher mucoadhesive strength of OM1 can be attributed to the greater hydrogen-bonding potential of Carbopol 934P, which forms strong interactions with mucin glycoproteins. Effective mucoadhesion is a desirable property, as it ensures prolonged gastric retention, localized action, and enhanced therapeutic efficiency against H. pylori infection.

 

Figure 7. USP Disintegration apparatus for invitro muco-adhesion test using rat mucosa

 

Table 7. Percent Muco-adhesion of OM1 and OM2

Formulation Code

Percent Muco-adhesion

OM1

76.36

OM2

67.27

Figure 8. Graph representing Percent muco-adhesion of OM1 and OM2

 

3.12 In Vitro Drug Release:

Dissolution studies in 0.1 N HCl (pH 1.2) revealed sustained drug release from both formulations for up to 12hours. OM1 exhibited a gradual release pattern, reaching 93.3% cumulative release at 12h, while OM2 released 87.6% over the same period. The controlled release behavior was attributed to the polymer matrix, which regulated diffusion of esomeprazole through the swollen microsphere structure. These results indicate that the microspheres are capable of maintaining prolonged therapeutic drug concentrations in the gastric environment, which is essential for effective H. pylori eradication.

 

Table 8. Percentage Drug release of OM1 and OM2

S. No

Time

Percentage Drug release of OM1

Percentage Drug release of OM2

1

0

0

0

2

0.5

4.839344

7.726232

3

1

14.58934

12.62916

4

2

22.18984

19.46016

5

3

34.51684

28.82916

6

4

38.50009

33.4386

7

5

41.22184

44.41512

8

6

50.01184

45.98796

9

7

57.75559

56.04036

10

8

63.33334

66.24816

11

9

68.49409

68.14056

12

10

73.65259

73.11876

13

11

83.40109

84.91836

14

12

93.31009

87.68376

 

3.13 Drug Release Kinetics:

Release data were fitted to different mathematical models to determine the mechanism of drug release. OM1 and OM2 both followed zero-order kinetics (R˛ > 0.99), suggesting a constant release rate independent of drug concentration. Additionally, good correlation was observed with the Korsmeyer–Peppas model (n ≈ 0.82), indicating a non-Fickian, anomalous diffusion mechanism involving both drug diffusion and polymer relaxation. The Higuchi model also showed acceptable fit, supporting the role of diffusion through the hydrated polymer matrix. Collectively, these results confirm that the formulations achieved sustained and controlled release, a crucial attribute for gastric-targeted delivery systems.

 

Table 9.  Release kinetics

Formulation

Zero Order

Higuchi Equation

Peppa’s Equation

r2

K0

r2

KH

r2

n

OM1

0.9936

7.883

0.9852

29.85

0.9952

0.824

OM2

0.9958

7.730

0.995

22.51

0.9976

0.820

 

3.14 Stability Studies:

Stability testing over one month at ambient laboratory conditions (24–28°C) showed no significant changes in the physical appearance, particle size, mucoadhesive properties, or drug content of the microspheres. FTIR spectra remained unchanged, indicating the absence of chemical degradation or polymer–drug interaction. Furthermore, probiotic viability remained stable within acceptable limits, confirming that the microsphere matrix provided adequate protection during storage. These results suggest that the optimized formulations possess good short-term stability and are suitable for further preclinical evaluation.

 

3.15 ANOVA Results:

Statistical analysis of the Box–Behnken design confirmed the significance of the selected models for all three responses (entrapment efficiency, particle size, and practical yield). For entrapment efficiency (Y1), the model F-value indicated strong influence of polymer interactions. Particle size (Y2) was significantly affected by both sodium alginate concentration and stirring speed, whereas practical yield (Y3) was largely governed by combined effects of polymer concentrations and stirring conditions. In all cases, the lack-of-fit was non-significant, validating the adequacy of the models. These results confirm the reliability of the experimental design for formulation optimization.

 

Table 10. ANOVA results for the response variable Y1 (entrapment efficiency).

Source

Sum of Squares

df

Mean Square

F-value

p-value

Model

731.88

9

81.32

10.10

0.0030

A-Polymer Alginate

2.00

1

2.00

0.2483

0.6335

B-Polymer Carbopol934

17.40

1

17.40

2.16

0.1850

C-Stirring Speed

0.4050

1

0.4050

0.0503

0.8290

AB

90.25

1

90.25

11.21

0.0123

AC

90.25

1

90.25

11.21

0.0123

BC

0.3600

1

0.3600

0.0447

0.8386

46.55

1

46.55

5.78

0.0472

484.32

1

484.32

60.13

0.0001

21.79

1

21.79

2.71

0.1440

Residual

56.38

7

8.05

Lack of Fit

10.51

3

3.50

0.3055

0.8213

Pure Error

45.87

4

11.47

Cor Total

788.26

16

 

3.16 Response Surface Mapping and Overlay Plot:

Three-dimensional response surface plots and two-dimensional contour plots illustrated the interactive effects of sodium alginate, Carbopol 934P, and stirring speed on formulation responses. Entrapment efficiency increased with higher polymer concentrations, while particle size was positively correlated with sodium alginate levels and stirring speed. Practical yield also improved with balanced polymer ratios.

 

The overlay plot highlighted a well-defined design space, with the yellow-shaded region representing optimal conditions. OM1 and OM2 formulations fell within this space, confirming their desirability. This optimization approach provided clear guidance on the critical process parameters necessary to achieve robust, reproducible, and clinically relevant formulations.

 

Table 11. ANOVA results for the response variable Y2 (Particle size)

Source

Sum of Squares

df

Mean Square

F-value

p-value

Model

3.04

9

0.3375

74.23

< 0.0001

significant

A-Polymer Alginate

0.8070

1

0.8070

177.50

< 0.0001

B-Polymer Carbopol

934

0.1141

1

0.1141

25.08

0.0016

C-Stirring Speed

0.1992

1

0.1992

43.81

0.0003

AB

0.0349

1

0.0349

7.67

0.0277

AC

0.8310

1

0.8310

182.77

< 0.0001

BC

0.0403

1

0.0403

8.85

0.0206

0.9642

1

0.9642

212.06

< 0.0001

0.0264

1

0.0264

5.82

0.0466

0.0086

1

0.0086

1.89

0.2116

Residual

0.0318

7

0.0045

Lack of Fit

0.0229

3

0.0076

3.41

0.1337

not significant

Pure Error

0.0090

4

0.0022

Cor Total

3.07

16

 

Table 12.  ANOVA results for the response variable Y3 (Practical Yield)

Source

Sum of Squares

df

Mean Square

F-value

p-value

Model

600.01

9

66.67

313.49

< 0.0001

significant

A-Polymer Alginate

22.88

1

22.88

107.60

< 0.0001

B-Polymer Carbopol

934

39.60

1

39.60

186.23

< 0.0001

C-Stirring Speed

130.98

1

130.98

615.89

< 0.0001

AB

92.16

1

92.16

433.36

< 0.0001

AC

3.01

1

3.01

14.15

0.0071

BC

56.25

1

56.25

264.50

< 0.0001

96.44

1

96.44

453.46

< 0.0001

130.71

1

130.71

614.65

< 0.0001

40.09

1

40.09

188.52

< 0.0001

Residual

1.49

7

0.2127

Lack of Fit

0.0227

3

0.0076

0.0207

0.9953

not significant

Pure Error

1.47

4

0.3665

Cor Total

601.50

16

 

Figure 9. 2D and 3D response surface plot showing the relationship between various levels of Sodium alginate Concentration and Carbopol 934 Concentration on entrapment efficiency

 

 

Figure 10. 2D and 3D response surface plot showing the relationship between various levels of Sodium alginate Concentration and Carbopol 934 Concentration on particle size

 

 

Figure 11. 2D and 3D response surface plot showing the relationship between various levels of Sodium alginate Concentration and Carbopol 934 Concentration on Practical Yield

 

4.16.1 Overlay Plot of the selected model:

The desirable region was also selected using overlay plotting, wherein the constraints for choosing an optimum formulation were further narrowed down, as indicated in Fig.12

Figure 12. Overview plot design space for the optimized formulations in two-dimensional regions

 

The optimized formulations were identified through graphical optimization. In the overlay plot (Fig. 12), the yellow-shaded region represents the design space, indicating the combination of factor levels that satisfy the desired criteria. The grey area corresponds to non-optimal experimental regions. The contour lines illustrate the boundary limits for each response variable. Within the design space, the selected polymer concentrations yielded microspheres with reduced particle size, high entrapment efficiency, and satisfactory practical yield, confirming the robustness of the optimization approach.

 

5. CONCLUSION:

The present study successfully developed and optimized mucoadhesive microspheres co-encapsulating esomeprazole and Lactobacillus acidophilus using a sodium alginate–Carbopol 934P matrix. Application of a Box–Behnken design enabled systematic optimization of formulation variables, leading to two robust formulations, OM1 and OM2, with high entrapment efficiency (>94%), excellent flow properties, and reproducible yields.

 

 

The microspheres demonstrated sustained drug release for up to 12 hours, following zero-order and non-Fickian diffusion kinetics, while maintaining strong mucoadhesion and significant probiotic protection in simulated gastric fluid. SEM confirmed a spherical porous morphology, and FTIR studies indicated compatibility among drug, probiotic, and excipients. Short-term stability evaluation confirmed that the formulations remained physically and chemically stable during storage.

 

Overall, the findings highlight the potential of probiotic-loaded mucoadhesive microspheres as a promising alternative strategy for the management of Helicobacter pylori–associated gastric disorders. By combining a proton pump inhibitor with probiotics in a controlled-release gastroretentive system, this approach addresses the limitations of conventional therapy, including poor stability of probiotics and frequent relapse due to incomplete eradication.

 

Future work should include in vivo studies to evaluate pharmacokinetics, colonization efficiency, and therapeutic efficacy, followed by clinical validation to establish translational potential.

 

Abbreviations                  

H. pylori                            Helicobacter pylori

SGF                                     Simulated Gastric Fluid

FTIR                                   Fourier Transform Infrared
                                             Spectroscopy

SEM                                    Scanning Electron Microscopy

UV                                       Ultraviolet

ANOVA                              Analysis of Variance

rpm                                     Revolutions Per Minute

µg/ml                                  Micrograms per Milliliter

μm                                       Micrometer

%EE                                   Percent Entrapment Efficiency

sIgA                                     Secretory Immunoglobulin A

IgG                                      Immunoglobulin G

 

6. ACKNOWLEDGEMENTS:

Authors are thankful to the Department of Pharmaceutical Sciences, Kurukshetra University, Kurukshetra for the support provided.

 

7. AUTHORS INFORMATION:

Authors and Affiliations

Department of Pharmaceutical Sciences, Kurukshetra University, Kurukshetra-136119, Haryana, India

Shubham Gautam, Rimpy Dahiya, Jaishree Sharma , Deepak Ranga & Surender Verma

 

8. CONTRIBUTIONS:

SB, RD, JS, DR and SV have equally contributed to this work. The authors read and approved the final manuscript.

 

9.COMPETING INTERESTS:

The authors declare that they have no competing interests.

 

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Received on 12.07.2025      Revised on 16.08.2025

Accepted on 17.09.2025      Published on 20.01.2026

Available online from January 27, 2026

Asian J. Pharm. Tech. 2026; 16(1):81-90.

DOI: 10.52711/2231-5713.2026.00012

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