Optimization of the spherical integrity for sustained-release alginate microcarriers-encapsulated doxorubicin by the Taguchi method

Hepatocellular carcinoma (HCC) is a prevalent cancer often diagnosed at advanced stages. Transarterial chemoembolization (TACE) is a minimally invasive treatment delivering chemotherapeutic drugs, such as doxorubicin (Dox), into the hepatic artery. Current commercial drug-loaded microspheres are expensive and non-biodegradable, leading to complications. Biodegradable microspheres offer advantages by preventing permanent embolization and reducing complications. Sodium alginate, a biocompatible and biodegradable polymer, is a promising candidate for microcarrier fabrication due to its safety profile and hydrophilic nature. Previous studies have shown the potential of Dox-loaded alginate microspheres for delayed drug release in the liver. However, optimizing parameters for achieving high spherical integrity and sustained-release capacity is crucial. This study aimed to identify optimal parameters for fabricating calcium alginate microcarriers using the Taguchi method, a statistical technique for optimizing experimental designs.

The literature review highlights the clinical importance of TACE for HCC treatment and the limitations of existing embolic agents. It emphasizes the need for biodegradable and biocompatible alternatives. The review discusses various polymers used in drug delivery systems, focusing on sodium alginate's properties, including biocompatibility, biodegradability, and hydrophilicity. Existing research on alginate microspheres for drug delivery and their in vivo behavior is also reviewed. The challenges of achieving uniform particle size and spherical integrity in alginate microsphere fabrication are addressed, leading to the rationale for employing the Taguchi method for optimization.

This study employed the Taguchi method to optimize the fabrication of calcium alginate microcarriers for sustained Dox release. Eight parameters were investigated using an L18 orthogonal array: cross-linking volume ratio (sodium alginate:CaCl₂), sodium alginate solution concentration, CaCl₂ solution concentration, collection distance, flow rate, stirring speed, syringe needle diameter, and hardening time. A total of 18 groups of microcarriers were prepared under different conditions. Particle size was analyzed, and the spherical integrity was assessed by a scoring system after 14 days of immersion in PBS. Signal-to-noise (S/N) ratios were calculated to determine the optimal parameter combination. Fourier-transform infrared spectroscopy (FTIR) was used to characterize the chemical structure of the microcarriers. Scanning electron microscopy (SEM) examined the surface morphology. Swelling rates were measured in PBS at pH 7.4 and pH 6.5. Dox encapsulation and loading efficiencies were determined spectrophotometrically. In vitro drug release was studied in PBS and PBS containing 10% FBS. Finally, in vitro anticancer activity was evaluated using Huh-7 and Hep-3B HCC cell lines, assessing cell viability using trypan blue exclusion.

The Taguchi method identified the optimal parameters for fabricating calcium alginate microcarriers with high spherical integrity: cross-linking volume ratio (sodium alginate:CaCl₂) = 0.1, sodium alginate solution = 2.5 wt%, CaCl₂ solution = 6 wt%, collection distance = 8 cm, flow rate = 30 mL/h, stirring speed = 150 rpm, syringe needle diameter = 0.25 mm, and hardening time = 2 h. FTIR confirmed the ionic cross-linking of sodium alginate with calcium chloride. SEM revealed a rougher surface for Dox-loaded microcarriers compared to those without Dox. Swelling studies showed pH sensitivity, with lower swelling rates at pH 6.5 (simulating the tumor microenvironment). Dox encapsulation and loading efficiencies were approximately 40.62% and 3.52%, respectively. In vitro drug release showed sustained release for approximately two weeks in PBS at 37°C. The microcarriers themselves were non-toxic to HCC cells. In vitro experiments demonstrated significant inhibition of HCC cell viability (around 70%) on day 12 after treatment with the Dox-loaded microcarriers.

The study successfully optimized the fabrication of calcium alginate microcarriers for sustained Dox release, addressing the limitations of existing commercial options. The use of the Taguchi method efficiently identified the crucial parameters influencing spherical integrity and drug release. The pH sensitivity of the microcarriers is advantageous for targeted drug delivery in the acidic tumor microenvironment. The sustained-release characteristics over two weeks, coupled with the non-toxicity of the microcarriers themselves, indicate their potential as an effective drug delivery system for TACE in HCC treatment. The results support further development and in vivo evaluation of these microcarriers.

This research demonstrated the successful optimization of biodegradable calcium alginate microcarriers for sustained Dox delivery using the Taguchi method. Optimal parameters resulted in microcarriers with high spherical integrity, pH sensitivity, and sustained drug release, effectively inhibiting HCC cell viability in vitro. These findings suggest the promising potential of these microcarriers as a novel drug delivery system for TACE in HCC treatment. Future research should focus on in vivo studies to confirm efficacy and safety and explore the potential of these microcarriers for other cancer types or drug delivery applications.

The study was limited to in vitro experiments. In vivo studies are necessary to validate the findings and assess the long-term effects and biodegradability of the microcarriers. The relatively small number of parameters investigated may not encompass all variables affecting microcarrier properties. The impact of variations in alginate molecular weight was not explored. The use of only two HCC cell lines limits the generalizability of the in vitro results. Further studies should investigate the interaction of the microcarriers with other components of the tumor microenvironment.