Preparation of Cross-Linked Sodium Alginate Microspheres with Different Metal Ions Using the Microfluidic Electrospray Technology

Summary

The protocol describes the preparation of sodium alginate microspheres cross-linked with different metal ions using a microfluidic device for drug carrier design. The antimicrobial properties and slow drug release of these microspheres were also investigated.

Abstract

Microspheres are micrometer-sized particles that can load and gradually release drugs via physical encapsulation or adsorption onto the surface and within polymers. In the field of biomedicine, hydrogel microspheres have been extensively studied for their application as drug carriers owing to their ability to reduce the frequency of drug administration, minimize side effects, and improve patient compliance. Sodium alginate (ALG) is a naturally occurring linear polysaccharide with three backbone glycosidic linkages. There are two auxiliary hydroxyl groups present in each of the moieties of the polymer, which have the characteristics of an alcohol hydroxyl moiety. The synthetic ALG units can undergo chemical cross-linking reactions with metal ions, forming a cross-linked network structure of polymer stacks, ultimately forming a hydrogel. Hydrogel microspheres can be prepared using a simple process involving the ionic cross-linking properties of ALG. In this study, we prepared ALG-based hydrogel microspheres (ALGMS) using a microfluidic electrodeposition strategy. The prepared hydrogel microspheres were uniformly sized and well-dispersed, owing to accurate control of the microfluidic electrospray flow. ALGMS cross-linked with different metal ions were prepared using a microfluidic electrospray technique combining microfluidic and high electric field, and its antimicrobial properties, slow drug release ability, and biocompatibility were investigated. This technology holds promise for application in advanced drug development and production.

Introduction

Drug delivery systems are a research hotspot in the field of bio-tissue engineering, aiming to improve drug delivery efficiency and efficacy and reduce adverse reactions and side effects¹. Among these systems, hydrogel microspheres, characterized by good biocompatibility, tunable mechanical properties, and functional plasticity, are one of the most commonly used vehicles for drug loading and delivery². They can be used for both slow and controlled release of drugs, provide good protective effects for drugs, avoid or minimize non-specific effects of drugs in other tissues, and target drug delivery to specific tissue struc....

Protocol

The blood used in the experiments was obtained from SPF-grade BALB/c female mice weighing 20-25 g and approximately 7 weeks old. The Animal Experimentation Ethics Committee of Zhejiang Shuren College approved all animal care and experimental procedures.

1. Solution preparation

1. Weigh ALG and dissolve in ultrapure water by stirring in a water bath at 50 °C to obtain 2% ALG solution.
2. Separately prepare mass fraction with 5% (or molar mass concentration is 0.3 M) solutions of CaCl₂, FeCl₃, ZnSO₄, and CuSO₄ in ultrapure water. Pour each solution separately in....

Results

Characterization of ALGMS cross-linked with different metal ions
The optical morphology of Ca-ALGMS, Cu-ALGMS, Zn-ALGMS, and Fe-ALGMS is shown in Figure 2, exhibiting good sphericity, smooth surface, uniform particle size distribution (Supplementary Figure 2) and excellent monodispersity. We further performed microscopic characterization using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis. As shown in

Discussion

In this protocol, we present a method for preparing ALGMS based on microfluidic electrospray technology. The method is simple to operate and yields a large number of microspheres with uniform roundness and controllable diameter. This approach offers convenience to researchers and can promote the research and application of hydrogel microspheres. In addition, by cross-linking with different metal ions, the stability and bioactivity of the ALGMS were improved. In the antimicrobial experiments, Cu-ALGMS and Zn-ALGMS exhibit.......

Materials

Name	Company	Catalog Number	Comments
120 mesh screen	Solarbio,China	YA0946
Alcohol burner	Solarbio,China	YA2320
BALB/c mice	Wukong Biotechnology,China
Bicinchoninic Acid Assay reagent	Meilunbio,China	MA0082
Bovine Serum Albumin	Lablead,China	9048-46-8
CaCl2  powder	Aladdin,China	10043-52-4
Calcein-AM/PI	Biosharp,China	BL130A
Centrifuge tubes	Corning,America	430290
CuSO4  powder	Jnxinyuehuagong,China	7758-99-8
DMEM	Gibicol,China	C11995500BT
FeCl3  powder	Aladdin,China	7705-08-0
Fetal Bovine Serum	HAKATA,China	HN-FBS
Glass tubes	Sartorius,Germany	CC0028
Light microscopy	Evidentscientific,Japan	BX53(LED)
Microfluidic syringe pump	Longerpump,England	LSP01-3A
NIH3T3	HyGyte,China	TCM-C752
Petri dish	Thermofisher,America	150464
Phosphate buffer saline	Thermofisher,America	3002
Scanning electron microscope	Thermofisher,America	Axia ChemiSEM
Sodium alginate powder	Bjbalb,China	Y13095
ZnSO4 powder	Jnxinyuehuagong,China	7733-02-0