Swelling characteristics of DNA polymerization gels.

The development of biomolecular stimuli-responsive hydrogels is important for biomimetic structures, soft robots, tissue engineering, and drug delivery. DNA polymerization gels are a new class of soft materials composed of polymer gel backbones with DNA duplex crosslinks that can be swollen by sequential strand displacement using hairpin-shaped DNA strands. The extensive swelling can be tuned using physical parameters such as salt concentration and biomolecule design. Previously, DNA polymerization gels have been used to create shape-changing gel automata with a large design space and high programmability. Here we systematically investigate how the swelling response of DNA polymerization gels can be tuned by adjusting the design and concentration of DNA crosslinks in the hydrogels or DNA hairpin triggers, and the ionic strength of the solution in which swelling takes place. We also explore the effect hydrogel size and shape have on the swelling response. Tuning these variables can alter the swelling rate and extent across a broad range and provide a quantitative connection between biochemical reactions and macroscopic material behaviour.

Multicomponent DNA Polymerization Motor Gels.

Hydrogels with the ability to change shape in response to biochemical stimuli are important for biosensing, smart medicine, drug delivery, and soft robotics. Here, a family of multicomponent DNA polymerization motor gels with different polymer backbones is created, including acrylamide-co-bis-acrylamide (Am-BIS), poly(ethylene glycol) diacrylate (PEGDA), and gelatin-methacryloyl (GelMA) that swell extensively in response to specific DNA sequences. A common mechanism, a polymerization motor that induces swelling is driven by a cascade of DNA hairpin insertions into hydrogel crosslinks. These multicomponent hydrogels can be photopatterned into distinct shapes, have a broad range of mechanical properties, including tunable shear moduli between 297 and 3888 Pa and enhanced biocompatibility. Human cells adhere to the GelMA-DNA gels and remain viable during ≈70% volumetric swelling of the gel scaffold induced by DNA sequences. The results demonstrate the generality of sequential DNA hairpin insertion as a mechanism for inducing shape change in multicomponent hydrogels, suggesting widespread applicability of polymerization motor gels in biomaterials science and engineering.

Photo-Enhanced Singlet Oxygen Generation of Prussian Blue-Based Nanocatalyst for Augmented Photodynamic Therapy.

Therapeutic effects of photodynamic therapy (PDT) remain largely limited because of tumor hypoxia. Herein, we report safe and versatile nanocatalysts (NCs) for endogenous oxygen generation and imaging-guided enhanced PDT. The NCs (named as PSP) are prepared by coating Prussian blue (PB) with mesoporous silica to load photosensitizer (zinc phthalocyanine, ZnPc), followed by the modification of polyethylene glycol chains. The inner PB not only acts like a catalase for hydrogen peroxide decomposition but also serves as a photothermal agent to increase the local temperature and then speed up the oxygen supply under near-infrared irradiation. The loaded ZnPc can immediately transform the formed oxygen to generate cytotoxic singlet oxygen upon the same laser irradiation due to the overlapped absorption between PB and ZnPc. Results indicate that the PSP-ZnPc (PSPZP) NCs could realize the photothermally controlled improvement of hypoxic condition in cancer cells and tumor tissues, therefore demonstrating enhanced cancer therapy by the incorporation of PDT and photothermal therapy.

In Situ One-Pot Synthesis of MOF-Polydopamine Hybrid Nanogels with Enhanced Photothermal Effect for Targeted Cancer Therapy.

Herein, a simple one-pot way is designed to prepare a type of multifunctional metal-organic framework (MOF)-based hybrid nanogels by in situ hybridization of dopamine monomer in the skeleton of MnCo. The resultant hybrid nanoparticles (named as MCP) show enhanced photothermal conversion efficiency in comparison with pure polydopamine or MnCo nanoparticles (NPs) synthesized under a similar method and, therefore, show great potential for photothermal therapy (PTT) in vivo. The MCP NPs are expected to possess T1 positive magnetic resonance imaging ability due to the high-spin Mn-N6 (S = 5/2) in the skeleton of MnCo. To improve the therapy efficiency as a PTT agent, the MCP NPs are further modified with functional polyethylene glycol (PEG) and thiol terminal cyclic arginine-glycine-aspartic acid peptide, respectively: the first one is to increase the stability, biocompatibility, and blood circulation time of MCP NPs in vivo; the second one is to increase the tumor accumulation of MCP-PEG NPs and improve their therapeutic efficiency as photothermal agent.

Biodegradable Core-shell Dual-Metal-Organic-Frameworks Nanotheranostic Agent for Multiple Imaging Guided Combination Cancer Therapy.

Metal-organic-frameworks (MOFs) possess high porosity, large surface area, and tunable functionality are promising candidates for synchronous diagnosis and therapy in cancer treatment. Although large number of MOFs has been discovered, conventional MOF-based nanoplatforms are mainly limited to the sole MOF source with sole functionality. In this study, surfactant modified Prussian blue (PB) core coated by compact ZIF-8 shell (core-shell dual-MOFs, CSD-MOFs) has been reported through a versatile stepwise approach. With Prussian blue as core, CSD-MOFs are able to serve as both magnetic resonance imaging (MRI) and fluorescence optical imaging (FOI) agents. We show that CSD-MOFs crystals loading the anticancer drug doxorubicin (DOX) are efficient pH and near-infrared (NIR) dual-stimuli responsive drug delivery vehicles. After the degradation of ZIF-8, simultaneous NIR irradiation to the inner PB MOFs continuously generate heat that kill cancer cells. Their efficacy on HeLa cancer cell lines is higher compared with the respective single treatment modality, achieving synergistic chemo-thermal therapy efficacy. In vivo results indicate that the anti-tumor efficacy of CSD-MOFs@DOX+NIR was 7.16 and 5.07 times enhanced compared to single chemo-therapy and single thermal-therapy respectively. Our strategy opens new possibilities to construct multifunctional theranostic systems through integration of two different MOFs.

Rapid Adsorption Enables Interface Engineering of PdMnCo Alloy/Nitrogen-Doped Carbon as Highly Efficient Electrocatalysts for Hydrogen Evolution Reaction.

The catalytic performance of Pd-based catalysts has long been hindered by surface contamination, particle agglomeration, and lack of rational structural design. Here we report a simple adsorption method for rapid synthesis (∼90 s) of structure-optimized Pd alloy supported on nitrogen-doped carbon without the use of surfactants or extra reducing agents. The material shows much lower overpotential than 30 wt % Pd/C and 40 wt % Pt/C catalysts while exhibiting excellent durability (80 h). Moreover, unveiled by the density functional theory (DFT) calculation results, the underlying reason for the outstanding performance is that the PdMnCo alloy/pyridinic nitrogen-doped carbon interfaces weaken the hydrogen-adsorption energy on the catalyst and thus optimize the Gibbs free energy of the intermediate state (ΔGH*), leading to a remarkable electrocatalytic activity. This work also opens up an avenue for quick synthesis of a highly efficient structure-optimized Pd-based catalyst.

Magnetically guided delivery of DHA and Fe ions for enhanced cancer therapy based on pH-responsive degradation of DHA-loaded Fe3O4@C@MIL-100(Fe) nanoparticles.

Dihydroartemisinin (DHA) has been investigated in cancer therapy for its reactive oxygen species (ROS) based cytotoxicity originated from interacting with ferrous ions that may reduce or eliminate the multidrug resistance commonly associated with conventional chemotherapy agents. However, synchronously delivery of hydrophobic DHA and Fe (Ⅲ) ions into tumor cells remains a major challenge. In this work, we develop novel Fe3O4@C@MIL-100(Fe) (FCM) nanoparticles for synchronously delivery of DHA and Fe (Ⅲ) for cancer therapy. The MOFs structure based on Fe (Ⅲ) carboxylate materials MIL-100 (Fe) holds great potential for storage/delivery of hydrophobic drug DHA. As a unique nanoplatform, the hybrid inorganic-organic drug delivery vehicles show pH-responsive biodegradation and synchronous releasing of DHA and Fe (Ⅲ) upon reaching tumor sites. The intracellular Fe (Ⅲ) will be reduced further to ferrous ion and interact with DHA to increase its cytotoxicity. The potential of this alternative anti-tumor modality is demonstrated in vivo due to an increased intracellular accumulation of DHA in tumor and activated mechanism via co-release of DHA and Fe (Ⅲ), especially under the guidance of an external applied magnetic field.

Controllable synthesis of dual-MOFs nanostructures for pH-responsive artemisinin delivery, magnetic resonance and optical dual-model imaging-guided chemo/photothermal combinational cancer therapy.

Theranostic nanoagents which integrate diagnostic and therapeutic moieties into a single platform have attracted broad attention in cancer therapy, however the development of more effective and less toxic diagnostic and therapeutic interventions is still of great urgency. Herein, novel core-shell PB@MIL-100(Fe) dual metal-organic-frameworks (d-MOFs) nanoparticles are fabricated and their combined theranostic effects in vitro and in vivo are investigated. The d-MOFs nanoparticles can serve as a T1-T2 dual-modal magnetic resonance imaging (MRI) contrast and fluorescence optical imaging (FOI) agent due to the existence of inner PB MOFs and outer MIL-100(Fe) MOFs. The artemisinin (a traditional Chinese anticancer medicine) with a high loading content of 848.4 mg/g is released from the d-MOFs upon tumor cellular endocytosis due to the pH-responsive degradation of outer MOFs in low pH lysosomes of tumor cells. Furthermore, the inner PB MOFs can be utilized for photothermal therapy due to its strong absorbance in NIR region. Under the guidance by such dual-modal imaging, in vivo photothermal and chemotherapy is finally carried out, achieving effective tumor ablation in an animal tumor model. Furthermore, histological analysis revealed that the drug delivery system had no obvious effect on the major organs of mice due to the low toxicity of both d-MOFs and artemisinin. The distinctive multimodal imaging capability, excellent synergistic therapy effect through the combined chemo-photothermal therapy together with the low toxicity of both d-MOFs and artemisinin endow the theranostic nanoagent a promising next generation of nanomedicine for efficient and safe cancer therapy.

Active and Durable Hydrogen Evolution Reaction Catalyst Derived from Pd-Doped Metal-Organic Frameworks.

The water electrolysis is of critical importance for sustainable hydrogen production. In this work, a highly efficient and stable PdCo alloy catalyst (PdCo@CN) was synthesized by direct annealing of Pd-doped metal-organic frameworks (MOFs) under N2 atmosphere. In 0.5 M H2SO4 solution, PdCo@CN displays remarkable electrocatalytic performance with overpotential of 80 mV, a Tafel slope of 31 mV dec(-1), and excellent stability of 10 000 cycles. Our studies reveal that noble metal doped MOFs are ideal precursors for preparing highly active alloy electrocatalysts with low content of noble metal.

Fe3O4@carbon@zeolitic imidazolate framework-8 nanoparticles as multifunctional pH-responsive drug delivery vehicles for tumor therapy in vivo.

Controlled drug release is a promising approach for cancer therapy due to its merits of reduced systemic toxicity and enhanced antitumor efficacy. Here, multifunctional Fe3O4@carbon@zeolitic imidazolate framework-8 (FCZ) hybrid nanoparticles (NPs) were successfully constructed. Owing to the porosity and acid-sensitivity of zeolitic imidazolate framework-8 (ZIF-8), FCZ NPs not only displayed an improved drug loading capacity compared to most of the polymeric nanocarriers, but also exhibited excellent pH-triggered release of doxorubicin (DOX) in vitro. Moreover, carbon dots (CDs) embedded in the porous carbon shell and superparamagnetic iron oxide nanocrystals could simultaneously function as intracellular fluorescence imaging and T2*-weighted magnetic resonance imaging (MRI) contrast agents, respectively. The results obtained from the MTT assay demonstrated good biocompatibility of FCZ NPs. DOX release experiments showed pH regulation-dominated drug release kinetics: a weak acidic pH in tumor areas could trigger sustained drug release, suggesting that FCZ NPs are ideal drug delivery systems. Moreover, the remarkable inhibition of tumor growth without side effects was confirmed in vivo. These results provide convincing evidence establishing the multifunctional FCZ NPs as promising candidates for tumor therapy.