Development of metal free carbon catalyst derived from Parthenium hysterophorus for the electrochemical detection of dopamine.

Parthenium hysterophorus, one of the seven most hazardous weeds is widely known for its allergic, respiratory and skin-related disorders. It is also known to affect biodiversity and ecology. For eradication of the weed, its effective utilization for the successful synthesis of carbon-based nanomaterial is a potent management strategy. In this study, reduced graphene oxide (rGO) was synthesized from weed leaf extract through a hydrothermal-assisted carbonization method. The crystallinity and geometry of the as-synthesized nanostructure are confirmed from the X-ray diffraction study, while the chemical architecture of the nanomaterial is ascertained through X-ray photoelectron spectroscopy. The stacking of flat graphene-like layers with a size range of ∼200-300 nm is visualized through high-resolution transmission electron microscopy images. Further, the as-synthesized carbon nanomaterial is advanced as an effective and highly sensitive electrochemical biosensor for dopamine, a vital neurotransmitter of the human brain. Nanomaterial oxidizes dopamine at a much lower potential (0.13 V) than other metal-based nanocomposites. Moreover, the obtained sensitivity (13.75 and 3.31 µA µM-1 cm-2), detection limit (0.6 and 0.8 µM), the limit of quantification (2.2 and 2.7 µM) and reproducibility calculated through cyclic voltammetry/differential pulse voltammetry respectively outcompete many metal-based nanocomposites that were previously used for the sensing of dopamine. This study boosts the research on the metal-free carbon-based nanomaterial derived from waste plant biomass.

Preparation of Ultrathin and Degradable Polymeric Films by Electropolymerization of 3-Amino-l-tyrosine.

Bioderived polymers are one of many current research areas that promise a sustainable future. Due to their unique properties, the bioderived polymer polydopamine has been in the spotlight over the last decades. Its ability to adhere to virtually any surface and its stability over a wide pH range as well as in several organic solvents make it a suitable candidate for various applications like coatings and biosensors. However, strong light absorption over a broad range of wavelengths and high quenching efficiency limit its uses. Therefore, new bioderived polymers with similar features to polydopamine but without fluorescence quenching properties are highly desirable. Herein, the electropolymerization of a bioderived analog of dopamine, 3-amino-l-tyrosine, is demonstrated. The resulting polymer, poly(amino-l-tyrosine), exhibits several characteristics complementary to or even exceeding those of polydopamine and its analog, polynorepinephrine, rendering poly(amino-l-tyrosine) attractive for the development of sensors and photoactive devices. Cyclic voltammetry, spectro-electrochemistry, and electrochemical quartz crystal microbalance measurements are applied to study the electrodeposition of this material, and the resulting films are compared to polydopamine and polynorepinephrine. Impedance spectroscopy reveals increased ion permeability of poly(amino-l-tyrosine) compared to polydopamine and polynorepinephrine. Moreover, the reduced fluorescence quenching of poly(amino-l-tyrosine) supports its use as coating for biosensors and organic semiconductors.

Dopamine-polyethyleneimine co-deposition cellulose filter paper for α-Glucosidase immobilization and enzyme inhibitor screening.

In this work, cellulose filter paper (CFP), which is inexpensive and commercially available, was used as the carrier, and the immobilized α-glucosidase was obtained by two steps: firstly, the surface of CFP was modified by polydopamine/polyethyleneimine (PDA/PEI) co-deposition method to obtain CFP-PDA/PEI with a uniform coating of rich positive charge; subsequently, α-glucosidase was immobilized on the CFP-PDA/PEI by electrostatic adsorption. The free enzyme and immobilized enzyme have the same optimal temperature (70℃) and pH (8.0), and their Km is similar, which is 2.2 and 2.8, respectively. These results show that the immobilization process does not change the properties of the enzyme greatly. The immobilized enzyme still maintains 75.6% of its initial activity after 10 repeated uses, showing good reusability. The excellent repeatability (RSD = 2.2%, n = 5) and the verification of competitive inhibitor (acarbose) illustrates the reliability of the immobilized enzymes for enzyme inhibitor screening. Finally, combined with CE, a screening method based immobilized α-glucosidase was proposed and applied to screen the α-glucosidase inhibitory from 10 kinds of Traditional Chinese medicines (TCMs) in vitro. The results indicated that the method was a very effective tool for screening potential α-glucosidase inhibitors from TCMs.

Immobilization of enzyme cocktails on dopamine functionalized magnetic cellulose nanocrystals to enhance sugar bioconversion: A biomass reusing loop.

A combined enzymatic treatment/acid hydrolysis technique was utilized to synthesize cellulose nanocrystals (CNCs) from sugar beet pulp. CNCs were functionalized with magnetite nanoparticles and dopamine making a versatile nano-carrier (DA/Fe3O4NPs@CNCs) for covalent enzyme immobilization. Oxygene/amine functionalities, high magnetization value, and specific surface area of DA/Fe3O4NPs@CNCs made it a reusable and green candidate for conjugation to hydrolytic enzyme cocktails (three cellulases, two hemicellulases, and their combinations) to prepare an innovative and practical nano-biocatalyst for biomass conversion. The conjugated enzymes showed an enhanced optimum temperature (∼ 10 °C), improved thermal stability, and shifted optimum pH toward alkaline pHs. Covalent attachment could successfully suppress the enzyme leaching and provide easy recovery/reuse of the nano-biocatalyst up to 10 cycles, with > 50% of initial activity. Application of the nano-biocatalyst in hydrolysis of rice straw and sugar beet pulp showed an increase (20-76%) in the yield of fermentable sugars compared to the free enzyme cocktails.

Neuroprotective Effects of Safflower Flavonoid Extract in 6-Hydroxydopamine-Induced Model of Parkinson's Disease May Be Related to its Anti-Inflammatory Action.

Safflower (Carthamus tinctorius. L.), a Chinese materia medica, is widely used for the treatment of cardiovascular and cerebrovascular diseases, with flavonoids being the major active components. Multiple flavonoids in safflower bind to Parkinson's disease (PD)-related protein DJ-1. Safflower flavonoid extract (SAFE) improved behavioral indicators in a 6-hydroxydopamine (6-OHDA)-induced rat model of PD; however, the underlying mechanisms remain unclear. We used a 6-OHDA-induced mouse model of PD and a primary neuron-astrocyte coculture system to determine the neuroprotective effects and mechanisms of SAFE. After three weeks of SAFE administration, behavioral indicators of PD mice were improved. SAFE regulated the levels of tyrosine hydroxylase (TH) and dopamine metabolism. It significantly inhibited the activation of astrocytes surrounding the substantia nigra and reduced Iba-1 protein level in the striatum of PD mice. SAFE reduced the plasma content of inflammatory factors and suppressed the activation of nod-like receptor protein 3 (NLRP3) inflammasome. In the coculture system, kaempferol 3-O-rutinoside and anhydrosafflor yellow B significantly improved neuronal survival, suppressed neuronal apoptosis, and reduced IL-1ß and IL-10 levels in the medium. Thus, SAFE showed a significant anti-PD effect, which is mainly associated with flavonoid anti-inflammatory activities.

Heat-Generating Iron Oxide Multigranule Nanoclusters for Enhancing Hyperthermic Efficacy in Tumor Treatment.

The development of heat-generating magnetic nanostructures is critical for the effective management of tumors using magnetic hyperthermia. Herein, we demonstrate that polyethylene glycol (PEG)-coated iron oxide (magnetite, Fe3O4) multigranule nanoclusters (PEG-MGNCs) can enhance the efficiency of hyperthermia-based tumor suppression in vitro and in vivo. MGNCs consisting of granules (crystallites) measuring 22.9 nm in diameter were prepared via the hydrothermal polyol method, followed by the surface modification of MGNCs with PEG-dopamine. The freshly prepared PEG-MGNCs exhibit 145.9 ± 10.2 nm diameter on average under aqueous conditions. The three-dimensional structures of PEG-MGNCs enhance the hyperthermic efficacy compared with PEGylated single iron-oxide nanoparticles (NPs), resulting in severe heat damage to tumor cells in vitro. In the SCC7 tumor-bearing mice, near-infrared fluorescence dye (Cy5.5)-labeled PEG-MGNCs are successfully accumulated in the tumor tissues because of NP-derived enhanced permeation and retention effect. Finally, the tumor growth is significantly suppressed in PEG-MGNC-treated mice after two-times heat generation by using a longitudinal solenoid, which can generate an alternating magnetic field under high-frequency (19.5 kA/m, 389 kHz) induction. This study shows for the first time that the PEG-MGNCs greatly enhance the hyperthermic efficacy of tumor treatment both in vitro and in vivo.

Compatibility of treprostinil sodium and dopamine hydrochloride during simulated Y-site administration.

PURPOSE: To evaluate the physical and chemical compatibilities of treprostinil sodium and dopamine hydrochloride. METHODS: Treprostinil sodium (4,000, 76,000, and 500,000 ng/mL) were mixed with dopamine hydrochloride (0.6, 3.2, 6, and 40 mg/mL). Samples were obtained at hours 0, 1, 2, and 4 for physical compatibility and chemical stability testing. Physical compatibility was assessed by visual examination and measurements of turbidity and pH. Drug concentrations were assessed using stability-indicating liquid chromatography mass spectrophotometry (LCMS) for treprostinil sodium and stability-indicating high-performance liquid chromatography (HPLC) for dopamine hydrochloride. RESULTS: Treprostinil sodium 4,000 and 76,000 ng/mL, when mixed with dopamine hydrochloride 0.6, 3.2, 6, and 40 mg/mL, were stable for 4 hours. Treprostinil sodium 500,000 ng/mL was stable when mixed with dopamine hydrochloride 0.6 mg/mL for 4 hours, but when mixed with dopamine hydrochloride 3.2, 6, and 40 mg/mL, significant precipitation was seen. CONCLUSION: Treprostinil sodium 4,000 and 76,000 ng/mL were stable for 4 hours during simulated Y-site coadministration with dopamine hydrochloride 0.6, 3.2, 6, and 40 mg/mL. Treprostinil sodium 500,000 ng/mL is stable when mixed with dopamine hydrochloride 0.6 mg/mL.

Size-Transformable Hyaluronan Stacked Self-Assembling Peptide Nanoparticles for Improved Transcellular Tumor Penetration and Photo-Chemo Combination Therapy.

Size-transformable nanomedicine has the potential to overcome systemic and local barriers, leading to efficient accumulation and penetration throughout the tumor tissue. However, the design of this type of nanomedicine was seldom based on active targeting and intracellular size transformation. Here, we report an intracellular size-transformable nanosystem, in which small and positively charged nanoparticles (<30 nm) prepared from the self-assembly of an amphiphilic hexadecapeptide derivative was coated by folic acid- and dopamine-decorated hyaluronan (HA) to form large and negatively charged nanoparticles (∼130 nm). This nanosystem has been proven to improve the blood circulation half-life of the drug and prevent premature intravascular drug leakage from the nanocarrier. Once accumulated in the tumor, the nanoparticles were prone to HA- and folic acid-mediated cellular uptake, followed by intracellular size transformation and discharge of transformed small nanoparticles. The size-transformable nanosystem facilitated the transcytosis-mediated tumor penetration and improved the internalization of nanoparticles by cells and the intracellular release of 7-ethyl-10 hydroxycamptothecin. With an indocyanine green derivative as the intrinsic component of the amphiphilic polymer, the nanosystem has exhibited additional theranostic functions: photoacoustic imaging, NIR-laser-induced drug release, and synergistic chemotherapy and phototherapy, leading to a 50% complete cure rate in a subcutaneous B16 melanoma model. This nanosystem with multimodalities and efficient tumor penetration has shown potentials in improving anticancer efficacy.

Tyrosinase-mediated dopamine polymerization modified magnetic alginate beads for dual-enzymes encapsulation: Preparation, performance and application.

In this study, a simple and efficient method to obtain entrapment of mixtures of double enzymes is developed. As a proof of principle, double enzymes (tyrosinase (TYR) and ß-glucosidase (ß-Glu)) were co-immobilized in magnetic alginate-polydopamine (PDA) beads using in situ TYR-mediated dopamine polymerization and internal setting strategy-mediated magnetic alginate-PDA gelation. The leakage of enzymes from the magnetic alginate beads was significantly reduced by exploiting the double network cross-linking of alginate and PDA, which was induced by the d-(+)-Gluconic acid δ-lactone (GDL) and TYR, respectively. The physicochemical properties of the prepared magnetic alginate beads were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. After that, the enzymatic reaction conditions and the performance of the entrapped TYR and ß-Glu, such as enzyme kinetics and inhibition kinetics, were investigated. The Michaelis-Menten constants (Km) of the entrapped TYR and ß-Glu were determined as 2.72 and 3.45 mM, respectively. The half-maximal inhibitory concentrations (IC50) of kojic acid and castanospermine for the entrapped TYR and ß-Glu were determined as 13.04 and 56.23 µM, respectively. Finally, the entrapped double enzymes magnetic alginate beads were successfully applied to evaluate the inhibitory potency of six kinds of tea polyphenols extracts. Black tea and white tea showed high inhibition activity against TYR were (36.14 ± 1.43)% and (36.76 ± 2.35)%, respectively, while the black tea and dark tea showed high inhibition activity against ß-Glu were (37.89 ± 6.70)% and (21.28 ± 4.68)%, respectively.

Preparation of electrospray ALG/PDA-PVP nanocomposites and their application in cancer therapy.

In this study, sodium alginate (ALG)/poly dopamine (PDA)-polyvinylpyrrolidone (PVP) nanocomposites was synthesized via a one-step electrostatic spraying method. The spinning solution of ALG and dopamine was electrostatically sprayed into an alkaline solution of PVP, calcium chloride and tris buffer (pH = 8.5), in which the gelation of ALG and the polymerization of dopamine could be simultaneously triggered. PDA hence produced possesses a high photothermal conversion efficiency, while the PVP that was facilely conjugated onto the surface of nanocomposites improves the colloidal stability and compatibility of the material. Moreover, the ALG renders the nanocomposite excellent drug (doxorubicine, DOX) loading capacity. Promisingly, the temperature increment during the PTT process could promote the DOX release, thus enhancing its therapeutic effect. The in vitro/in vivo biosafety and tumor treatment experiments further corroborate that the ALG/PDA-PVP nanocomposites have remarkable biocompatibility and synergism for tumor hyperthermia and chemotherapy. Consequently, such a one-step electrospray strategy provides a new way for designing nanomaterials and is expected to significantly promote the development of organic photothermal therapeutic agents with excellent bio-compatibility.

Synthesis, Purification, and Selective ß2-AR Agonist and Bronchodilatory Effects of Catecholic Tetrahydroisoquinolines from Portulaca oleracea.

A green, biomimetic, phosphate-mediated Pictet-Spengler reaction was used in the synthesis of three catecholic tetrahydroisoquinolines, 1, 2, and 12, present in the medicinal plant Portulaca oleracea, as well as their analogues 3-11, 13, and 14, with dopamine hydrochloride and aldehydes as the substrates. AB-8 macroporous resin column chromatography was applied for purification of the products from the one-step high-efficacy synthesis. It eliminated the difficulties in the isolation of catecholic tetrahydroisoquinolines from the aqueous reaction system and unreacted dopamine hydrochloride. Activity screening in CHO-K1/Gα15 cell models consistently expressing α1B-, ß1-, or ß2-adrenergic receptors indicated that 12 and 2, compounds that are present in P. oleracea, possessed the most potent ß2-adrenergic receptor agonist activity and 2 was a selective ß2-adrenergic receptor agonist at the concentration of 100 µM. Both 12 and 2 exhibited dose-dependent bronchodilator effects on the histamine-induced contraction of isolated guinea-pig tracheal smooth muscle, with EC50 values of 0.8 and 2.8 µM, respectively. These findings explain the scientific rationale of P. oleracea use as an antiasthmatic herb in folk medicine and provide the basis for the discovery of novel antiasthma drugs.

A design for the photoelectrochemical detection of miRNA-221 based on a tungsten diselenide-cysteine-dopamine nanoprobe coupled with mismatched catalytic hairpin assembly target recycling with ultra-low background noise.

A strategy for the photoelectrochemical detection of miRNA with ultra-low background noise was developed using tungsten diselenide-cysteine-dopamine (WSe2/Cys/DA) as a nanoprobe coupled with mismatched catalytic hairpin assembly target recycling. A superior detection limit of 3.3 aM toward miRNA-221 was achieved.

Injectable and Near-Infrared-Responsive Hydrogels Encapsulating Dopamine-Stabilized Gold Nanorods with Long Photothermal Activity Controlled for Tumor Therapy.

Gold nanorods (AuNRs) are confirmed to have excellent and repeated photothermal properties under near-infrared (NIR)-light irradiation above 780 nm. However, AuNRs easily leaked out from local pathological tissues and circulated in the body, reducing photothermal therapy (PTT) efficacy. By complexing AuNRs with a scaffold via interactions, AuNRs might be dispersed in the scaffold and fixed in the tumor site. Thus, based on the mussel-mimetic adhesion concept, AuNRs were designed to be coated with polydopamine (PDA), and then the prepared polydopamine-coated AuNRs (AuNR-PDA) were incorporated into a thermosensitive injectable hydrogel composed of ß-glycerophosphate-bound chitosan (CGP) and dopamine-modified alginate (Alg-DA) efficiently. Due to the strong interactions between PDA and polymers, AuNR-PDA could be immobilized stably and evenly into the obtained CGP/Alg-DA/AuNR composite hydrogel, which can avoid overheating locally or leaking out. The sol-gel transition temperature of the composite hydrogel was adjusted to the body temperature at around 37 °C to be conveniently injectable in vivo. With NIR irradiation at 808 nm of wavelength, the composite hydrogel was locally heated quickly to over 50 °C depending on controlling the irradiation powers and times. Moreover, the in vitro cytotoxicity test of the composite hydrogel showed good biocompatibility to normal cells but obvious suppression to tumor cells' growth under multiple times of photothermal therapy. Furthermore, the in vivo antitumor test demonstrated the obvious suppression to tumor growth of the CGP/Alg-DA/AuNR composite hydrogel under multiple PTTs. Therefore, the injectable CGP/Alg-DA/AuNR hydrogel could be a promising candidate for the long-term repeated photothermal treatment of tumors.

A carbon paste electrode modified with Al2O3-supported palladium nanoparticles for simultaneous voltammetric determination of melatonin, dopamine, and acetaminophen.

The authors have modified a carbon paste electrode with Al2O3-supported palladium nanoparticles (PdNP@Al2O3) to obtain a sensor for simultaneous voltammetric determination of melatonin (MT), dopamine (DA) and acetaminophen (AC). The PdNP@Al2O3 was characterized by scanning electron microscopy and energy-dispersive X-ray spectra. The sensor can detect DA, AC, MT and their mixtures by giving distinct signals at working voltages of typically 236, 480 and 650 mV (vs. Ag/AgCl), respectively. Differential pulse voltammetric peak currents of DA, AC and MT increase linearly in the 50 nmol L-1 - 1.45 mmol L-1, 40 nmol L-1 -1.4 mmol L-1, and 6.0 nmol L-1 - 1.4 mmol L-1 concentration ranges. The limits of detection are 36.5 nmol L-1 for DA, 36.5 nmol L-1 for AC, and 21.6 nmol L-1 for MT. The sensor was successfully used to detect the analytes in (spiked) human serum and drug samples. Graphical abstract Schematic presentation of Al2O3-supported palladium nanoparticles (PdNP@Al2O3) for modification of a carbon paste electrode (CPE) to develop a voltammetric sensor for the simultaneous determination of dopamine (DA), acetaminophen (AC) and melatonin (MT).

A tyrosinase-induced fluorescence immunoassay for detection of tau protein using dopamine-functionalized CuInS2/ZnS quantum dots.

Rapid, highly sensitive detection of tau protein and other neurodegenerative biomarkers remains a significant hurdle for diagnostic tests for Alzheimer's disease. In this work, we developed a novel tyrosinase (TYR)-induced tau aptamer-tau-tau antibody (anti-tau) sandwich fluorescence immunoassay to detect tau protein that used dopamine (DA)-functionalized CuInS2/ZnS quantum dots as the fluorophore. CuInS2/ZnS core/shell quantum dots with high luminescence, low toxicity, and excellent biocompatibility were successfully fabricated and decorated with DA through amide conjugation. Meanwhile, TYR was conjugated with anti-tau by a click reaction. When DA-functionalized CuInS2/ZnS quantum dots were added to the sandwich system, TYR catalyzed the transformation of DA to dopamine quinone, which acted as an effective electron acceptor and triggered fluorescence quenching. The fluorescence intensity of the immunoassay based on DA-functionalized CuInS2/ZnS quantum dots shows good performance in terms of linearity with the logarithm of tau protein concentration, with a linear concentration range from 10 pM to 200 nM. This work is the first to use a TYR-induced fluorescence immunoassay for the rapid detection of tau protein, paving a new way for the detection of disease biomarkers. Graphical abstract.

Rapid and Superior Bacteria Killing of Carbon Quantum Dots/ZnO Decorated Injectable Folic Acid-Conjugated PDA Hydrogel through Dual-Light Triggered ROS and Membrane Permeability.

One of the most difficult challenges in the biomedical field is bacterial infection, which causes tremendous harm to human health. In this work, an injectable hydrogel is synthesized through rapid assembly of dopamine (DA) and folic acid (FA) cross-linked by transition metal ions (TMIs, i.e., Zn2+ ), which was named as DFT-hydrogel. Both the two carboxyl groups in the FA molecule and catechol in polydopamine (PDA) easily chelates Zn2+ to form metal-ligand coordination, thereby allowing this injectable hydrogel to match the shapes of wounds. In addition, PDA in the hydrogel coated around carbon quantum dot-decorated ZnO (C/ZnO) nanoparticles (NPs) to rapidly generate reactive oxygen species (ROS) and heat under illumination with 660 and 808 nm light, endows this hybrid hydrogel with great antibacterial efficacy against Staphylococcus aureus (S. aureus, typical Gram-positive bacteria) and Escherichia coli (E. coli, typical Gram-negative bacteria). The antibacterial efficacy of the prepared DFT-C/ZnO-hydrogel against S. aureus and E. coli under dual-light irradiation is 99.9%. Importantly, the hydrogels release zinc ions over 12 days, resulting in a sustained antimicrobial effect and promoted fibroblast growth. Thus, this hybrid hydrogel exhibits great potential for the reconstruction of bacteria-infected tissues, especially exposed wounds.

Highly photoluminescent N, P doped carbon quantum dots as a fluorescent sensor for the detection of dopamine and temperature.

In recent times, fluorescent carbon quantum dots (CQDs) as an optical sensor have attained massive attention owing to their excellent optical properties. In current investigation, our group presented an easy and economical methodology to synthesize the nitrogen and phosphorous doped carbon quantum dots (N, P doped CQDs) for sensing dopamine (DA) and temperature in aqueous medium. The synthesized CQDs were characterized by using XRD, XPS, TEM, UV-Vis, FT-IR and fluorescence techniques. The N, P doped CQDs were synthesized via one-step microwave digestion method by using citric acid, ethylenediamine and urea phosphate as precursors. This method established the noble water solubility, good optical performances and fluorescence thermosensitivity of N, P doped CQDs. Also, N, P doped CQDs demonstrated a wide linear range of 10-500 µM (R2 = 0.994) and offered an electrifying detection limit of 0.021 µM for quantifying the dopamine. Moreover, this sensor possessed a good sensitivity, reversibility and linearity in the range of 10-70 °C. In addition, the CQDs sensing system repel the interference from probable foreign substances in real sample analysis, and attained good recoveries, which revealed the tremendous selectivity and adequate accuracy of the carbon quantum dots for sensing dopamine. The proposed N, P doped CQDs are simple as well as effective optical nanosensor and clasps venerable potential to widen the applications in analysis of biomolecules and other areas.

Hexagonal polypyrrole nanosheets from interface driven heterogeneous hybridization and self-assembly for photothermal cancer treatment.

Hexagonal polypyrrole (PPy) nanosheets with highly ordered lateral orientation were developed by the generation and directed self-assembly of dopamine induced FeOOH-PPy heterostructures on nanoscale THF/water interfaces. The size-controlled nanosheets possess attractive photothermal conversion properties, which facilitate efficient photothermal inhibition of cancer cells.

Preparation and properties of dopamine-modified alginate/chitosan-hydroxyapatite scaffolds with gradient structure for bone tissue engineering.

Three-dimensional (3D) homogenous scaffolds composed of natural biopolymers have been reported as superior candidates for bone tissue engineering. There are still remaining challenges in fabricating the functional scaffolds with gradient structures to similar with natural bone tissues, as well as high mechanical properties and excellent affinity to surround tissues. Herein, inspired by the natural bone structure, a gradient-structural scaffold composed of functional biopolymers was designed to provide an optimized 3D environment for promoting cell growth. To increase the interactions among the scaffolds, dopamine (DA) was employed to modify alginate (Alg) and needle-like nano-hydroxyapatite (HA) was prepared with quaternized chitosan as template. The obtained dopamine-modified alginate (Alg-DA) and quaternized chitosan-templated hydroxyapatite (QCHA) were then used to fabricate the porous gradient scaffold by "iterative layering" freeze-drying technique with further crosslinking by calcium ions (Ca2+ ). The as-prepared Alg-DA/QCHA gradient scaffolds were possessed seamlessly integrated layer structures and high levels of porosity at around 77.5%. Moreover, the scaffolds showed higher compression modules (1.7 MPa) than many other biopolyermic scaffolds. The gradient scaffolds showed appropriate degradation rate to satisfy with the time of the bone regeneration. Both human chondrocytes and fibroblasts could adhesive and growth well on the scaffolds in vitro. Furthermore, an excellent osteogenetic activity of the gradient scaffold can effectively promote the regeneration of the bone tissue and accelerate the repair of the bone defects in vivo, compared with that of the scaffold with the homogenous structure. The novel multilayered scaffold with gradient structure provided an interesting option for bone tissue engineering. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1615-1627, 2019.