Alginate Network Research Articles

Physical appearance and arsenate removal efficiency of Fe(III)-modified clinoptilolite beads affected by alginate-wet-granulation process parameters

Fe(III)-modified clinoptilolite (Fe-Clin) was encapsulated into beads using sodium alginate (NaAlg) and Ca2+ and/or Fe3+ ions by a simple wet-gelation method to obtain Fe-Clin beads. The impacts of various parameters including mixture pH, type of cross-linker, concentration of cross-linking solution and initial mass ratio of NaAlg to Fe-Clin were investigated on the appearance of beads and also their performance in As(V) removal. To increase the net negative surface charge of alginate, pH value of the mixture was essentially adjusted to the level 12–13. This strong alkaline condition increased the ability of alginate mixture to form stable and well-shaped beads. Ca2+ acting as a cross-linker showed a less impact on the beads shape than Fe3+ due to the strong tendency of Fe3+ ions to react with oxygen atoms in carboxylate groups of alginate. A loosely cross-linked Ca2+-alginate network formed during preparation of Fe-Clin beads was considered as the main reason for their lower arsenate removal efficiency of 29.4% rather than 60.5% for those cross-linked in FeCl3. In addition, there were found optimal values of FeCl3 cross-linking solution concentration and initial mass ratio of NaAlg: Fe-Clin as 2% (w/v) and 1:4, respectively to achieve the maximum As(V) removal efficiency of 82%.

Design of an Interpenetrating Polymeric Network Hydrogel Made of Calcium-Alginate from a Thermos-Sensitive Pluronic Template as a Thermal-Ionic Reversible Wound Dressing.

Polymer-based hydrogels demonstrate superior performance when used as wound dressing. An ideal dressing should possess an active healing function, absorb wound exudates, and provide a moist interface on the wound for rapid injury repair and the prevention of pain and injury during replacement of the dressing. Thus, the aim of this study was to develop a novel, reversible, smart, interpenetrating polymeric network (IPN) by utilizing the thermosensitive network of pluronic F127 (PF127) as a template to regulate the conformation of calcium-ion-crosslinked alginate. We found that the IPN hydrogels formed soft and elastic thermosensitive networks, retaining their form even after absorbing a large amount of wound exudate. The exterior of the hydrogels was made up of a rigid calcium alginate network that supported the entire hydrogel, promoting the stability of the vascular endothelial growth factor (VEGF) payload and controlling its release when the hydrogel was applied topically to wounds. Raman spectroscopy confirmed the layered structure of the hydrogel, which was found to easily disintegrate even after moderate rinsing of the wound with cold phosphate-buffered saline. Taken together, these results show that the IPN hydrogel developed in this study could be a promising delivery platform for growth factors to accelerate wound healing.

Fluidic embedding of additional macroporosity in alginate-gelatin composite structure for biomimetic application

Biomimetic characteristics of hydrogel scaffold are tuned in this study utilizing the synergy of alginate, gelatin, and microfluidically embedded voids. Superposition of alginate and gelatin polymer networks results in additional rigidity, which can be tuned by introduction of voids, and thereby allowing faster release of pore pressure through movement of aqueous phase through the pore network. More importantly, voids enabled the cells to penetrate from the surface of seeding into the depth of the scaffold and proliferate there, as demonstrated for MDA MB 231 breast cancer cells. The uniform voids, generated by the microfluidic device, self-align creating uniform macroporosity within the gel structure, get readily filled by the media due to hydrophilicity, and extend the characteristics of composite uniformly across the entire scaffold.

Inelasticity increases the critical strain for the onset of creases on hydrogels

When a soft material (gel, elastomer, or biological tissue) is compressed beyond a critical strain, its smooth surface forms creases. During this process, a material particle near a crease undergoes a path of load and unload. If the material is elastic, the load and unload do not dissipate energy, and the crease sets in at a critical strain about 0.35. If the material is inelastic, however, the load and unload dissipate energy, and the crease is expected to set in at a higher critical strain. Here we study the effect of inelasticity on the onset of creases using alginate-polyacrylamide hydrogels. Such a hydrogel consists of two interpenetrating polymer networks: a polyacrylamide network of covalent crosslinks, and an alginate network of ionic crosslinks. The former is stretchy and elastic, while the latter unzips at a small stretch and causes inelasticity. We prepare alginate-polyacrylamide hydrogels with various degrees of inelasticity by varying the concentration of alginate. Our experiment confirms that larger degree of inelasticity leads to larger critical strain for crease. This study shows an example that the chemistry of materials affects the mechanics of creases.

Fabrication and characterization of Ca(II)-alginate-based beads combined with different polysaccharides as vehicles for delivery, release and storage of tea polyphenols

In order to enhance the encapsulation efficiency of tea polyphenols (TP) and retard their diffusion from alginate hydrogel beads, we structured alginate network by coating or adding fillers. In the present study, alginate-based blends consisting of inulin, Arabic gum, or chitosan were prepared for assessment of the best formulation. Results indicated that encapsulation efficiencies of TP in plain alginate bead as well as beads reinforced with inulin, Arabic gum and chitosan were 38.51%, 36.48%, 48.56% and 57.76%, respectively, revealing that selected appropriate filler materials could indeed increase the encapsulation efficiency of TP. Additionally, the release profile of TP revealed that the porosity of alginate beads could not efficiently retard the diffusion of polyphenols from beads. However, alginate bead coated by chitosan gave the most retarded release of TP both in water and in the simulated gastrointestinal conditions. Moreover, TP encapsulated in the obtained beads could partly protect them from degradation during storage. Our results suggested that selected appropriate fillers or coating materials can indeed enhance the encapsulation efficiency of TP and retard their release, which could promote the application of TP as a functional ingredient in the food industry.

Controlled release of fertilizers from Ca(II)-alginate matrix modified by yerba mate (Ilex paraguariensis) waste

Yerba mate (Ilex paraguariensis) is an infusion traditionally drunk in many countries of South America. Along its industrial manufacture, a fine yerba mate powder represents a considerable proportion of the total production, consisting of an industrial by-product not safe for human consumption, rich in minerals, that could be useful as organic compost. In line with current bioeconomic trends, here we present the recycling of yerba mate industrial by-products into urea, potassium and phosphate-containing capsules as an environmentally friendly strategy for the design of controlled-release fertilizers. The capsule matrix is based on Ca(II)-alginate with a final yerba mate powder (YMP) content of 83% w/w. The aim of this work was to study the kinetics of mineral fertilizers release both in soil and water, along with an exhaustive macro and microstructural characterization (PIM, DSC, TGA, SEM-EDX, X ray scan tomography and SAXS) to allow the analysis of structure/function relationships. The encapsulation efficiency and release in water of phosphorous were affected, being significantly lower than urea and potassium and releasing under different mechanism. Retention and degradation in soil was mainly related to capsule structure, as well as their thermal properties. The incorporation of different fertilizer induced structural changes in Ca(II)-alginate network as assessed by SAXS.

Fabricating Tough Interpenetrating Network Cryogels with DNA as the Primary Network for Biomedical Applications.

This work investigates a sequential strategy to develop DNA-based hydrogel scaffolds with interpenetrating polymeric network. The scaffolds were formed via a two-step procedure. First, a covalently cross-linked DNA-based cryogel was formed by the chemical reaction between DNA strands and a bifunctional cross-linker, polyethylene glycol diepoxide at subzero temperatures. In the second step, alginate chains were absorbed into the preformed macroporous DNA cryogel network, followed by ionic cross-linking with divalent calcium ions. The individual and synergistic effects of covalent and ionic cross-linkings on mechanical and physical properties of the IPN cryogel were tested. The IPN cryogels were able to sustain large deformations higher than 95% of strain under compressive forces without exhibiting any failure. Addition of a physically cross-linked alginate network to the covalently linked DNA cryogel significantly enhanced its toughness and energy dissipation compared to the covalent network alone. The formulated hydrogels also exhibited excellent biocompatibility with human stem cells. Overall, this DNA-based IPN cryogel has the potential to be used as a biomaterial scaffold for a diverse range of tissue engineering applications.

Biphasic Double-Network Hydrogel With Compartmentalized Loading of Bioactive Glass for Osteochondral Defect Repair

Periarticular injury usually causes the defects of superficial cartilage and the underlying subchondral bone. Although some efficacious outcomes have been achieved by the existing therapeutic methods both in clinics and research, like symptomatic treatment, microfracture surgery, and tissue engineering technology, they still present specific disadvantages and complications. To improve this situation, we designed a biphasic (bi-) scaffold aiming to repair the structure of cartilage and subchondral bone synchronously. The scaffold consisted of a superior double-network (DN) hydrogel layer and a lower bioactive glass (BG) reinforced hydrogel layer, and the DN hydrogel included glycol chitosan (GC) and dibenzaldhyde functionalized poly(ethylene oxide) network, and sodium alginate (Alg) and calcium chloride (CaCl2) network. To investigate its effectiveness, we applied this biphasic scaffold to repair osteochondral full-thickness defects in rabbit models. We set up six observation groups in total, including Untreated group, Microfracture group, BG only group, DN gel group, bi-DN gel group, and bi-DN/TGF-β gel group. With a follow-up period of 24 weeks, we evaluated the treatment effects by gross observation, micro-CT scan and histological staining. Besides, we further fulfilled the quantitative analysis of the data from ICRS score, O’Driscoll score and micro-CT parameters. The results revealed that neat GC/Alg DN hydrogel scaffold was only conductive to promoting cartilage regeneration and neat BG scaffold merely showed the excellent ability to reconstruct subchondral bone. While the biphasic scaffold performed better in repairing osteochondral defect synchronously, exhibiting more well-integrated cartilage-like tissue with positive staining of toluidine blue and col II immunohistochemistry, and more dense trabecular bone connecting closely with the surrounding host bone. Therefore, this method possessed the clinical application potential in treating articular injury, osteochondral degeneration, osteochondral necrosis, and sclerosis.

Molecular characterisation of hot moulded alginate gels as a delivery vehicle for the release of entrapped caffeine

This work explores the process of alginate molecule crosslinking to form cohesive gels that were induced by the addition of calcium ions at various stoichiometric equivalents. Polysaccharide gels were used as a delivery vehicle for the study of transport phenomena of entrapped caffeine as the bioactive compound. Initial physicochemical characterisation through FTIR and WAXD of the alginate matrix showed successful inclusion of caffeine in the bulk system. Rheological analysis in the form of dynamic oscillation in-shear highlighted issues of developing network integrity and its eventual collapse with increasing levels of the crosslinker. Swelling in neutral solvent (water molecules) yielded information on the molecular features of the gel, as determined by the Flory-Rehner theoretical framework. Analysis of molecular transport with modified Fickian diffusion equations showed anomalous behaviour and a sustained release of caffeine. Overall, alteration in mesh size and diffusion parameters can be ascribed to the microstructural changes controlled by calcium crosslinking and the formation of junction zones in the alginate network.

Facile fabrication of carboxylated cellulose nanocrystal–MnO2 beads for high-efficiency removal of methylene blue

As a sustainable nanomaterial, cellulose nanocrystal (CNC) based adsorbents exhibited great potential in wastewater treatment due to their high specific surface area, easy surface functionalization and excellent mechanical strength. Herein, a facile, green and energy-efficient method was proposed to fabricate the CNC/manganese dioxide (MnO2)/alginate (ALG) beads. The hybrid CNC/MnO2 nanocomposites were prepared by a simple and fine purification “one-pot” synthesis process and then anchored onto ALG networks directly to form the triphase beads in a continuous and automated mode. Interestingly, the CNC/MnO2/ALG beads exhibited excellent adsorption and oxidative degradation of methylene blue after a regeneration process. The decolorizing efficiency and capacity could reach up to 99.8% and 136.7 mg/g, respectively. Meanwhile, the CNC/MnO2/ALG beads can maintain their high efficiency (~ 95% of initial value) even after 10 cycles, indicating excellent recyclability and durability. It provides us a new route to design novel hybrid materials for environmental remediation.

A self-supported gel filter membrane for dye removal with high anti-fouling and water flux performance

Traditional polymer filtration membranes are easily polluted in operation. An interpenetrating polymer network (IPN) gel was designed as a self-supported filter membrane. This IPN gel was structured by a Ca2+ crosslinked alginate network and a covalently crosslinked poly(acrylamide) network. Polyethylene glycol-polyhedral oligomeric silsesquioxane (PEG-POSS) was hybridised into the gel to optimise performance. Our research demonstrated that the uniform dispersion of PEG-POSS in the matrix improved membrane performance comprehensively due to its nanoscale and amphipathicity. The membranes showed well mechanical properties and sewage treatment capacity. Under the operation pressure 2 bar, the water flux of membranes could keep 11.7 L m−2 h−1 in long-term use. When dealing with the high concentration (500 mg L−1) of Methylene blue and Congo red solution, the rejection of dye could reach 93% and 95% respectively. In anti-fouling experiments with 8000 mg L−1 protein emulsion as the fouling source, the membranes keep over 80% initial flux after 10 times of water-emulsion cycle.

Synthesis and characterization of curcumin loaded alginate microspheres for drug delivery

Curcumin loaded alginate microspheres (Cur-AMs) have the potential to be used in drug delivery system for therapeutic treatment. This study reports the development of the controlled size Cur-AMs using an emulsification/gelation method and the curcumin release mechanism. The Cur-AMs was synthesized by water-in-oil emulsion technique followed by the gelation of the emulsion droplets. The size of the microspheres was tailored by alginate concentration. The particle size, morphology, encapsulation efficiency (EE), curcumin release profile, in vitro degradation and antimicrobial activity of Cur-AMs were investigated. The Cur-AMs were in a spherical shape with the average diameter ranging from 20.2 μm to 72.3 μm. The EE was proportional to alginate concentration and reached 53.36% at 5% w/v of alginate concentration. The Cur-AMs showed a sustained drug release over 672 h. The weight loss percentage of the microspheres reached 89.6% after 42 days of degradation. The drug release mechanism of Cur-AMs initiated with the diffusion of curcumin though out the swell-able alginate network, followed by the disintegration of alginate matrix. Additionally, the Cur-AMs was susceptible to S. aureus ATCC 12600 and resistance to E. coli ATCC 25922. The obtained Cur-AMs have promising potentials in therapeutic delivery via parenteral injection route.

Encapsulation and Release Control of Fish Pathogen Utilizing Cross-Linked Alginate Networks and Clay Nanoparticles for Use with a Potential Oral Vaccination

Streptococcus parauberis is utilized as an oral vaccine by first inactivating the cells with formalin to produce formalin- killed cells (FKC) and then encapsulating them with polymer beads consisting of a cross-linked alginate-Ca2+ network. The encapsulation efficiency and media-dependent release are controlled by pre-treating the FKC with two types of clay nanoparticles: kaolinite (KA) and layered double hydroxide (LDH). The addition of LDH induced large agglomerates of FKC, and the KA enhanced the dispersion of FKC. The differences in the dispersibility of the FKC upon the use of clay nanoparticles was determined to strongly affect the encapsulation efficiency and release properties. The FKC + LDH mixture exhibited a slightly reduced encapsulation efficiency compared to the FKC alone. However, FKC + KA exhibited a dramatically improved encapsulation efficiency. In terms of the media-dependent release, the alginate beads were found to be fairly stable under gastric conditions and in deionized water with or without clay nanoparticles, preserving most of the encapsulated FKC. The intestine was the final target organ for FKC vaccination, and release at the site varied according to the use of clay nanoparticles. Both clays seemed to enhance the release of FKC, the cumulative amount being 3.6 times and 1.3 times larger for LDH and KA, respectively, than was shown with only FKC encapsulated beads.

Three-Dimensional Bioprinting of Perfusable Hierarchical Microchannels with Alginate and Silk Fibroin Double Cross-linked Network.

Vascularization is essential for the regeneration of three-dimensional (3D) bioprinting organs. As a general method to produce microfluidic channels in 3D printing constructs, coaxial extrusion has attracted great attention. However, the biocompatible bioinks are very limited for coaxial extrusion to fabricate microchannels with regular structure and enough mechanical properties. Herein, a hybrid bioink composed of alginate (Alg) and silk fibroin (SF) was proposed for 3D bioprinting of microchannel networks based on coaxial extrusion. The rheological properties of the bioink demonstrated that the hybrid Alg/SF bioink exhibited improved viscosity and shear thinning behavior compared with either pure Alg or SF bioink and had similar storage and loss modulus in a wide range of shear frequency, indicating a sound printability. Using a coaxial extrusion system with calcium ions and Pluronic F127 flowing through the core nozzle as cross-linkers, the Alg/SF bioink could be extruded and deposited to form a 3D scaffold with interconnected microchannels. The regular structure and smooth pore wall of microchannels inside the scaffold were demonstrated by optical coherence tomography. Micropores left by the rinse of F127 were observed by scanning electron microscope, constituting a hierarchical structure together with the microchannels and printed macropores. Fourier transform infrared spectroscopy analysis proved the complete rinse of F127 and the formation of β-sheet SF structure. Thus, Alg/SF could form a double cross-linked network, which was much stronger than the pure Alg network. Moreover, cells in the Alg/SF scaffold showed higher viability and proliferation rate than in the Alg scaffold. Therefore, Alg/SF is a promising bioink for coaxial extrusion-based 3D bioprinting, with the printed microchannel network beneficial for complex tissue and organ regeneration.

Nanofibrils vs nanocrystals bio-nanocomposites based on sodium alginate matrix: An improved-performance study

To develop bio-nanocomposites using natural biopolymers, nanocomposite films were prepared based on sodium alginate and kapok nanofibrils (CNFs). CNFs when subjected to TEMPO-mediated oxidation gave rise to cellulose nanocrystals (TOCNCs), with carboxyl groups at the surface (Ka/Kb = 3.64). The differences between the two types of nanocelluloses (nanofibrils and nanocrystals) and their impact in the preparation of bio-nanocomposites, were studied. When incorporated in the matrix, the CNFs particles have the tendency to form surface aggregation (Ka/Kb = 2.37), distorting the alginate network, creating heterogeneous films, with high surface roughness (Sa = 29.37 nm), porosity (Dp = 0.087 cm2/min) and vulnerability to heat. The TOCNCs present good dispersion creating a 3D network, which forms uniform (Dp = 0.122 cm2/min) and homogeneous films, with smooth surface (Sa = 16.83 nm). The ultrasonication treatment facilitated the dispersion improving the interfacial interaction between the reinforcing phase and the matrix. The results show the reinforcement potential of kapok nanocellulose in an industrially and medically important biopolymer, sodium alginate, especially when TOCNCs and ultrasonication were used.

Strong alginate/reduced graphene oxide composite hydrogels with enhanced dye adsorption performance

The alginate/reduced graphene oxide composite hydrogels with hierarchical network structures were synthesized through the hydrothermal treatment of graphene oxide and alginate in an aqueous solution followed by ionically cross-linking of metal ions. The network of reduced graphene oxide was prepared via self-assembly of graphene nanosheets in the presence of alginate during the hydrothermal process; then, the polymer network of alginate was obtained by ionically cross-linking, forming the composite hydrogel. The effect of metal ions on the physical properties of the composite hydrogels was investigated. The prepared alginate/reduced graphene oxide composite hydrogel cross-linked by Fe3+ ions showed higher compression strength and lower swelling ratio. Moreover, due to the synergetic interaction between graphene and alginate, the composite hydrogels exhibited the improved dye adsorption performance, especially for cationic dyes. Even after ten adsorption/desorption cycles, the composite hydrogels can retain more than 90% dye adsorption capacity. The results indicated that the composite hydrogel with good stability, adsorption and regeneration ability could be a promising candidate for dye removal from waste aqueous solutions.

Polyvinyl Alcohol/Sodium Alginate Hydrogels Incorporated with Silver Nanoclusters via Green Tea Extract for Antibacterial Applications

ABSTRACT Silver-based nanoparticles and biomaterials have extensive biomedical applications owing to their unique antimicrobial properties. Thus, green and facile synthesis of such materials is highly desirable. This study reports an antibacterial hydrogel based on polyvinyl alcohol/sodium alginate network with the incorporation of silver nanoparticles (AgNPs), which is greenly synthesized by reductive metabolites obtained from the leaves of green tea. The ‘flower-shape’ AgNPs were acquired, it formed a mono-disperse system with a distinct uniform interparticle separation. The average size of AgNPs varied from 129.5 to 243.6 nm, which could be regulated by using different volumes of the green tea extract. Zeta potentials of the AgNPs were from −39.3 mV to −20.3 mV, indicating the moderate stability of the particles in water. In the next stage, the antibacterial polyvinyl alcohol/sodium alginate hydrogels were fabricated by incorporating prepared AgNPs. Scanning Electron Microscopy (SEM) images showed that the porous structure was obtained, and Energy Dispersive X-Ray (EDX) analysis confirmed that the AgNPs were uniformly dispersed in the polymer network. The hydrogels exhibited superior water absorption properties, which were characterized by a high swelling ratio (500–900%) and fast equilibrium. The hydrogels also exhibited good antimicrobial activity in assays with Gram-positive bacteria Escherichia coli and Gram-negative bacteria Staphylococcus aureus. To sum up, a process for the green preparation of antibacterial hydrogels based on AgNPs derived from tea leaves as a conveniently available cheap local agricultural product was established.

Tough, stretchable and compressive alginate-based hydrogels achieved by non-covalent interactions.

In this study, two alginate-based hydrogels with good mechanical strength, toughness and resilience were synthesized by hydrophobic interaction and coordination bonding. Sodium alginate/poly(acrylamide) semi-interpenetrating network (NaAlg/PAM semi-IPN) hydrogels were first synthesized through the micelle copolymerization of acrylamide and stearyl methacrylate in the presence of sodium alginate, then calcium alginate/poly(acrylamide) double network (CaAlg/PAM DN) hydrogels were prepared by immersing the as-prepared NaAlg/PAM semi-IPN hydrogels in a CaCl2 solution. FT-IR and XPS results revealed NaAlg/PAM semi-IPN hydrogels and CaAlg/PAM DN hydrogels were successfully synthesized through non-covalent interactions. The tensile strength of CaAlg/PAM DN hydrogels could reach 733.6 kPa, and their compressive strengths at 80% strain are significantly higher than those of the corresponding NaAlg/PAM semi-IPN hydrogels, which is attributed to the alginate network crosslinked by Ca2+. The dual physically crosslinked CaAlg/PAM DN hydrogels can achieve fast self-recovery, and good fatigue resistance, which is mainly assigned to energy dissipation through dynamic reversible non-covalent interactions in both networks. The self-healing ability, swelling behavior and morphology of the synthesized alginate-based hydrogels were also evaluated. This study offers a new avenue to design and construct hydrogels with high mechanical strength, high toughness and fast self-recovery properties, which broadens the current research and application of hydrogels.

A conductive PEDOT/alginate porous scaffold as a platform to modulate the biological behaviors of brown adipose-derived stem cells.

The development of three-dimensional conductive scaffolds is vital to support the adhesion, proliferation and myocardial differentiation of stem cells in cardiac tissue engineering. Herein, we describe a facile approach for preparing a poly(3,4-ethylenedioxythiophene)/alginate (PEDOT/Alg) porous scaffold with a wide range of desirable properties. In the PEDOT/Alg scaffold, chemically crosslinked alginate networks are formed using adipic acid hydrazide as the crosslinker, and PEDOT is synthesized in situ in the alginate matrix simultaneously. PEDOT exists in the alginate matrix as particles and its morphology can be modulated by adjusting the ratio of PEDOT/alginate. The results also show that the swelling properties, degradation behaviors, mechanical strength and conductivity of the PEDOT/Alg scaffold can be controlled via adjusting the PEDOT/alginate ratio. The introduction of PEDOT can overcome the brittle nature of the pure alginate scaffold. Moreover, the PEDOT/Alg scaffold exhibits excellent conductivity (as high as 6 × 10-2 S cm-1). The introduction of PEDOT improves the protein absorption capacity of the alginate scaffold. To explore its potential application in cardiac tissue engineering, brown adipose-derived stem cells (BADSCs) are seeded in the prepared PEDOT/Alg porous scaffold. The results suggest that the PEDOT/Alg porous scaffold can support the attachment and proliferation of BADSCs. Moreover, it is beneficial for the cardiomyogenic differentiation of BADSCs, especially under electrical stimulation. Overall, we conclude that the PEDOT/Alg porous scaffold may represent an ideal platform to modulate the biological behaviors of BADSCs.

Transcriptome sequencing of Saccharina japonica sporophytes during whole developmental periods reveals regulatory networks underlying alginate and mannitol biosynthesis

BackgroundAlginate is an important cell wall component and mannitol is a soluble storage carbon substance in the brown seaweed Saccharina japonica. Their contents vary with kelp developmental periods and harvesting time. Alginate and mannitol regulatory networks and molecular mechanisms are largely unknown.ResultsWith WGCNA and trend analysis of 20,940 known genes and 4264 new genes produced from transcriptome sequencing of 30 kelp samples from different stages and tissues, we deduced that ribosomal proteins, light harvesting complex proteins and “imm upregulated 3” gene family are closely associated with the meristematic growth and kelp maturity. Moreover, 134 and 6 genes directly involved in the alginate and mannitol metabolism were identified, respectively. Mannose-6-phosphate isomerase (MPI2), phosphomannomutase (PMM1), GDP-mannose 6-dehydrogenase (GMD3) and mannuronate C5-epimerase (MC5E70 and MC5E122) are closely related with the high content of alginate in the distal blade. Mannitol accumulation in the basal blade might be ascribed to high expression of mannitol-1-phosphate dehydrogenase (M1PDH1) and mannitol-1-phosphatase (M1Pase) (in biosynthesis direction) and low expression of mannitol-2-dehydrogenase (M2DH) and Fructokinase (FK) (in degradation direction). Oxidative phosphorylation and photosynthesis provide ATP and NADH for mannitol metabolism whereas glycosylated cycle and tricarboxylic acid (TCA) cycle produce GTP for alginate biosynthesis. RNA/protein synthesis and transportation might affect alginate complex polymerization and secretion processes. Cryptochrome (CRY-DASH), xanthophyll cycle, photosynthesis and carbon fixation influence the production of intermediate metabolite of fructose-6-phosphate, contributing to high content of mannitol in the basal blade.ConclusionsThe network of co-responsive DNA synthesis, repair and proteolysis are presumed to be involved in alginate polymerization and secretion, while upstream light-responsive reactions are important for mannitol accumulation in meristem of kelp. Our transcriptome analysis provides new insights into the transcriptional regulatory networks underlying the biosynthesis of alginate and mannitol during S. japonica developments.