This work was supported by a Zhejiang Shuren University research project (2023R053 and 2023KJ237).

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
<ol>
	<li>Weigh ALG and dissolve in ultrapure water by stirring in a water bath at 50 &#176;C to obtain 2% ALG solution.</li>
	<li>Separately prepare mass fraction with 5% (or molar mass concentration ...

Developing Sodium Alginate Hydrogel Microspheres for Biomedical Use

<ol>
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No conflicts of interest are to be disclosed.

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...

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 structures3. Therefore, hydrogel microspheres have become a new and efficient drug delivery system, with research in this field gradually emerging4.
Hydrogel microspheres are typically synthesized from biodegradable materials, including polysaccharides, proteins, and natural polymers5. Among them, ALG is a biocompatible, biodegradable polysaccharide extracted from marine brown algae6. Its molecular chain contains free hydroxyl and carboxyl groups that can crosslink with most divalent or multivalent cations to form a water-insoluble hydrogel structure with a three-dimensional network5. The hydrogel microspheres formed by ALG can be converted into negatively charged polyelectrolytes in neutral and alkaline solutions. This repulsion between negative charges causes the microspheres to swell, allowing the release of the encapsulated active ingredient or drug. These properties have led to the consideration of ALG microspheres as promising drug carriers widely used for drug loading and controlled release7.
Various methods exist for the preparation of hydrogel microspheres. Traditional ALGMS preparation methods usually include the sol-gel method or the emulsion-sol method. These methods involve steps such as precipitation, co-precipitation, and gelation reactions to obtain the target microspheres8. In recent years, with the continuous development of microfluidic technology, the microfluidic electrospray method has gradually become an efficient and precise microsphere preparation method9. This method utilizes microfluidic technology to electrospray a polymer solution through a microfine nozzle to form micrometer-sized droplets and microspheres during the subsequent curing or cross-linking process10. Compared to the traditional method, microfluidic electrospray offers precise control of microsphere particle size and morphology by adjusting parameters such as solution flow rate, voltage, and fine nozzle size11. It also enables high-speed continuous preparation of microspheres, improving preparation efficiency and maintaining mild reaction conditions. In addition, ALGMS can be prepared to possess various functions, such as controlled-release drugs and loaded catalysts, enabling their easy application in various fields.
Here, we present a protocol for the preparation of ALG microspheres using the microfluidic electrospray method. The process involves passing an ALG solution through a microfluidic device and subjecting it to electrospray. The resulting droplets were collected in the solution containing different metal ions (Ca2+, Cu2+, Zn2+, and Fe3+) to initiate the cross-linking reaction. This reaction improves the stability and adhesion of the microspheres and endows them with different functionalities. This method is easy to perform, and the synthesized microspheres exhibit good size uniformity in their morphology. In addition, we investigated their antimicrobial properties, slow drug-release ability, and biocompatibility. This protocol will be useful for further drug development and production.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>120 mesh screen</td>
			<td>Solarbio,China</td>
			<td>YA0946</td>
			<td></td>
		</tr>
		<tr>
			<td>Alcohol burner</td>
			<td>Solarbio,China</td>
			<td>YA2320</td>
			<td></td>
		</tr>
		<tr>
			<td>BALB/c mice</td>
			<td>Wukong Biotechnology,China</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Bicinchoninic Acid Assay reagent</td>
			<td>Meilunbio,China</td>
			<td>MA0082</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine Serum Albumin</td>
			<td>Lablead,China</td>
			<td>9048-46-8</td>
			<td></td>
		</tr>
		<tr>
			<td>CaCl2&#160; powder</td>
			<td>Aladdin,China</td>
			<td>10043-52-4</td>
			<td></td>
		</tr>
		<tr>
			<td>Calcein-AM/PI</td>
			<td>Biosharp,China</td>
			<td>BL130A</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge tubes</td>
			<td>Corning,America</td>
			<td>430290</td>
			<td></td>
		</tr>
		<tr>
			<td>CuSO4&#160; powder</td>
			<td>Jnxinyuehuagong,China</td>
			<td>7758-99-8</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>Gibicol,China</td>
			<td>C11995500BT</td>
			<td></td>
		</tr>
		<tr>
			<td>FeCl3&#160; powder</td>
			<td>Aladdin,China</td>
			<td>7705-08-0</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum</td>
			<td>HAKATA,China</td>
			<td>HN-FBS</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass tubes</td>
			<td>Sartorius,Germany</td>
			<td>CC0028</td>
			<td></td>
		</tr>
		<tr>
			<td>Light microscopy</td>
			<td>Evidentscientific,Japan</td>
			<td>BX53(LED)</td>
			<td></td>
		</tr>
		<tr>
			<td>Microfluidic syringe pump</td>
			<td>Longerpump,England</td>
			<td>LSP01-3A</td>
			<td></td>
		</tr>
		<tr>
			<td>NIH3T3</td>
			<td>HyGyte,China</td>
			<td>TCM-C752</td>
			<td></td>
		</tr>
		<tr>
			<td>Petri dish</td>
			<td>Thermofisher,America</td>
			<td>150464</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate buffer saline</td>
			<td>Thermofisher,America</td>
			<td>3002</td>
			<td></td>
		</tr>
		<tr>
			<td>Scanning electron microscope</td>
			<td>Thermofisher,America</td>
			<td>Axia ChemiSEM</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium alginate powder&#160;</td>
			<td>Bjbalb,China</td>
			<td>Y13095</td>
			<td></td>
		</tr>
		<tr>
			<td>ZnSO4 powder</td>
			<td>Jnxinyuehuagong,China</td>
			<td>7733-02-0</td>
			<td></td>
		</tr>
	</tbody>
</table>

preparation of cross-linked sodium alginate microspheres with different metal ions using the microfluidic electrospray technology

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.

Author Spotlight: Advancing Therapeutics with Biocompatible Sodium Alginate Hydrogel Microspheres

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

Hydrogen microspheres are characterized by good compatibility, design flexibility, and high degree of customization. They have a broad application protector in biomedical fields such as therapeutic drug delivery and the construction of TC repair discoveries. In this study, we prepared hydrogen microspheres using a simple microfluidic device.Recently we have been trying to use hydrogen microspheres loaded with some small molecules from traditional Chinese medicine to promote all the healing. In this study, we found that zinc and copper ion cross-link the sodium alginate microspheres have good anti-microbial properties and thus copper ARGMS, and zinc ARGMS are suitable for the treatment of bacterial infectious diseases.

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 <strong clas...

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.

Microspheres are micrometer-sized particles that can load and gradually release drugs via physical encapsulation or adsorption onto the surface and within ...

preparation-cross-linked-sodium-alginate-microspheres-with-different

Research

JoVE Journal

Bioengineering

701 Views.  Zhejiang Shuren University. Hydrogen microspheres are characterized by good compatibility, design flexibility, and high degree of customization. They have a broad application protector in biomedical fields such as therapeutic drug delivery and the construction of TC repair discoveries. In this study, we prepared hydrogen microspheres using a simple microfluidic device.Recently we have been trying to use hydrogen microspheres loaded with some small molecules from traditional Chinese medicine to promote all the hea...