Rose Bengal-Chitosan Nanocomposites for Oral Administration

Abstract

Rose Bengal (RB) holds promise for therapeutic applications in the gastrointestinal (GI) tract but faces significant limitations due to poor bioavailability and stability in the GI environment. This in vitro proof-of-concept study aimed to develop an oral drug delivery system using self-assembled RB-chitosan (RBCS) nanocomposites formed via electrostatic interactions. RBCS nanocomposites exhibited high drug loading efficiency (87%) and a uniform particle size (~443 nm), with physicochemical analyses confirming molecular interactions and structural stability. However, in vitro studies revealed poor and highly variable drug release in simulated gastric fluids (SGFs), underlining the need for further optimization. To address these limitations, RBCS nanocomposites were encapsulated within well-established alginate beads (AlgBs). Among the tested systems, RBCS20-AlgBs were selected as the optimal one, forming a gastroresistant platform. Encapsulation mitigated burst release, enhanced structural integrity, and enabled sustained RB release under intestinal conditions. Swelling studies demonstrated that RBCS20-AlgBs maintained controlled hydration, preventing premature disintegration. Mathematical modeling indicated a matrix relaxation-driven release mechanism, with RBCS20-AlgBs demonstrating improved reproducibility compared to RB-loaded AlgBs (RB-AlgBs). Future studies should focus on evaluating in vivo performance to confirm the system's efficacy for oral administration.

Keywords: Rose Bengal; chitosan; gastrointestinal release; nanocomposites; oral administration.

Figure 1

Schematic representation of the formulation process for RBCS nanocomposites encapsulated in AlgBs (RBCS-AlgBs). The process involves the self-assembly of RBCS nanocomposites via electrostatic interaction (Step 1), followed by encapsulation in AlgBs (Step 2) to enhance stability and enable controlled release for oral delivery. Created with Biorender.com.

Figure 2

Methods tested for preparing RBCS-AlgBs. Method (A): RBCS were homogenized with alginate and dropped in CaCl₂ solution. Method (B): RBCS were isolated by basification and centrifugation, homogenized with alginate solution, and dropped in CaCl₂ solution. Created with Biorender.com.

Figure 3

RBCS particle size distribution. (A) Size distribution data. (B) Scatter plot showing the mean particle size (nm) for each RBCS, with statistical analysis performed using one-way ANOVA and Tukey’s post hoc test (**** p-value < 0.0001) (n = 12).

Figure 4

Microscopy characterization of RBCS-20. (A) non-freeze-dried RBCS-20, (B) freeze-dried RBCS-20 and (C) freeze-dried RBCS-20 by SEM.

Figure 5

Physicochemical characterization of RBCS-20 and raw materials. (A) DSC thermograms. (B) TGA thermograms. (C) FT-IR spectra.

Figure 6

In vitro release profiles of RBCS-20. (A) Release in buffer solutions. (B) Release in SGFs.

Figure 7

Microscopy characterization of different RB-loaded AlgBs. (A) RB-AlgBs: (A1) non-freeze-dried, (A2) freeze-dried and (A3) freeze-dried by SEM. (B) RBCS20AlgBs: (B1) non-freeze-dried, (B2) freeze-dried and (B3) freeze-dried by SEM.

Figure 8

Physicochemical characterization of different RB-loaded AlgBs and raw materials. (A) DSC thermograms. (B) TGA thermograms. (C) FT-IR spectra.

Figure 9

Swelling behavior of RB-AlgBs and RBCS20-AlgBs under simulated GI conditions over 6 h (n = 4). (A) Change in size and (B) weight over time. Data were analyzed using one-way ANOVA with Tukey’s post hoc test. Statistical significance * p < 0.05; ** p < 0.01 *** p < 0.001; **** p < 0.0001.

Figure 10

In vitro release profiles of RB-AlgBs and RBCS20-AlgBs. (A) Release in buffer solutions. (B) Release in SGFs.