DNA Release from Fe 3+ ‐Cross‐Linked Alginate Films Triggered by Logically Processed Biomolecular Signals: Integration of Biomolecular Computing and Actuation

Dual Cross-Linked Stimuli-Responsive Alginate-Based Hydrogels

Sodium alginate with different molecular weights (55, 170, and 320 kg mol-1) were chemically modified by grafting methacrylic moieties onto the hydroxyl groups of the alginate backbone. The methacrylation was optimized to obtain different degrees of modification. Chemically cross-linked hydrogels were obtained following UV-light irradiation in the presence of a photoinitiator. The swelling behavior and the mechanical properties were observed to depend on both the degree of methacrylation and the alginate molecular weight. Due to the chain entanglement present in high-viscosity sodium alginate, lower degrees of modification were required to tune the hydrogel properties. Moreover, in the presence of Ca2+, secondary cross-linking was introduced by the coordination of the alginate guluronate moieties with the Ca2+ ions. The addition of this secondary cross-linking caused fast volume shrinkage and a reinforcement of the mechanical properties. The secondary cross-linking was reversible, and the hydrogels regained their original shape for at least three cycles. Additionally, the dual cross-linked network can be used to induce adhesion between hydrogels and serve as a building block for self-folding actuators.

Cell-Like Capsules with "Smart" Compartments

Eukaryotic cells have inner compartments (organelles), each with distinct properties and functions. One mimic of this architecture, based on biopolymers, is the multicompartment capsule (MCC). Here, MCCs in which the inner compartments are chemically unique and "smart," i.e., responsive to distinct stimuli in an orthogonal manner are created. Specifically, one compartment alone is induced to degrade when the MCC is contacted with an enzyme while other compartments remain unaffected. Similarly, just one compartment gets degraded upon contact with reactive oxygen species generated from hydrogen peroxide (H₂ O₂ ). And thirdly, one compartment alone is degraded by an external, physical stimulus, namely, by irradiating the MCC with ultraviolet (UV) light. All these specific responses are achieved without resorting to complicated chemistry to create the compartments: the multivalent cation used to crosslink the biopolymer alginate (Alg) is simply altered. Compartments of Alg crosslinked by Ca²⁺ are shown to be sensitive to enzymes (alginate lyases) but not to H₂ O₂ or UV, whereas the reverse is the case with Alg/Fe³⁺ compartments. These results imply the ability to selectively burst open a compartment in an MCC "on-demand" (i.e., as and when needed) and using biologically relevant stimuli. The results are then extended to a sequential degradation, where compartments in an MCC are degraded one after another, leaving behind an empty MCC lumen. Collectively, this work advances the MCC as a platform that not only emulates key features of cellular architecture, but can also begin to capture rudimentary cell-like behaviors.

Stimulation-Inhibition of Protein Release from Alginate Hydrogels Using Electrochemically Generated Local pH Changes

The electrochemically controlled release of proteins was studied in a Ca²⁺-cross-linked alginate hydrogel deposited on an electrode surface. The electrochemical oxidation of ascorbate or reduction of O₂ was achieved upon applying electrical potentials +0.6 or -0.8 V (vs Ag/AgCl/KCl 3 M), respectively, resulting in decreasing or increasing pH locally near an electrode surface. The obtained local acidic solution resulted in the protonation of carboxylic groups in the alginate hydrogel and, as a result, the formation of a hydrophobic shrunken hydrogel film. Conversely, the produced alkaline local environment resulted in a hydrophilic swollen hydrogel film. The release of the proteins was effectively inhibited from the shrunk hydrogel and activated from the swollen hydrogel film. Overall, the electrochemically produced local pH changes allowed control over the biomolecule release process. While the release inhibition by applying +0.6 V was always effective and could be maintained as long as the positive potential was applied, the release activation was different depending on the protein molecular size, being more effective for smaller species, and molecule charge, being more effective for negatively charged species. The repetitive change from the inhibited to stimulated state of the biomolecule release process was obtained upon cyclic application of oxidative and reductive potentials (+0.6 V ↔ -0.8 V). The alginate hydrogel film shrinking-swelling as well as the protein release process were studied and visualized using a confocal fluorescent microscope. In order to be observed, an external surface of the alginate film and the loaded protein molecules were labeled with different fluorescent dyes, which then produced colored fluorescent images under a confocal microscope.

Catalyst-Based Biomolecular Logic Gates

Regulatory processes in biology can be re-conceptualized in terms of logic gates, analogous to those in computer science. Frequently, biological systems need to respond to multiple, sometimes conflicting, inputs to provide the correct output. The language of logic gates can then be used to model complex signal transduction and metabolic processes. Advances in synthetic biology in turn can be used to construct new logic gates, which find a variety of biotechnology applications including in the production of high value chemicals, biosensing, and drug delivery. In this review, we focus on advances in the construction of logic gates that take advantage of biological catalysts, including both protein-based and nucleic acid-based enzymes. These catalyst-based biomolecular logic gates can read a variety of molecular inputs and provide chemical, optical, and electrical outputs, allowing them to interface with other types of biomolecular logic gates or even extend to inorganic systems. Continued advances in molecular modeling and engineering will facilitate the construction of new logic gates, further expanding the utility of biomolecular computing.

Nanoreactor activated in situ for starvation-chemodynamic therapy of breast cancer

The nano-drug delivery system activated by tumor microenvironment (TME) can effectively treat tumors with low-toxicity. Based on high level of reductive GSH in TME and different coordination properties of Fe ions, this project intended to prepare a GSH-activated cascade catalytic nanoreactor for breast cancer treatment using Fe³⁺/Fe²⁺ as the molecular switch. In this study, the glucose oxidase (GOx) loaded iron alginate nano hydrogel (FeAlg/GOx) was prepared by the simple one-step titration method. Results showed that FeAlg/GOx could remain stable during in vivo circulation to avoid hypoglycaemia. When it reached targeted tumor site, reductive GSH can reduce Fe³⁺ to Fe²⁺. Thereafter, FeAlg/GOx nanogel was broken and GOx was released to consume the essential nutrient glucose (Glu) to achieve tumor starvation therapy. Next, the substrate H₂O₂ generated by the reaction between GOx and Glu can be catalyzed by Fe²⁺ to produce highly cytotoxic •OH in situ, which could further kill tumor cells. The in vivo pharmacodynamics results demonstrated that compared with the control group (V/V0 = 8.36 ± 1.73), FeAlg/GOx group showed the most significant anti-tumor effect with V/V0 of 3.08 ± 1.06. In conclusion, this "inactivated" FeAlg/GOx nanogel can be converted into "activated" therapeutic substances in situ to achieve starvation-chemodynamic combined treatment for breast cancer.

Current Advances in Multifunctional Nanocarriers Based on Marine Polysaccharides for Colon Delivery of Food Polyphenols

Inflammatory bowel disease (IBD) has been considered as a chronic disease that is difficult to cure and needs lifelong treatment. Marine polysaccharides with good biocompatibility and biodegradability, mucoadhesion, sensitivity to external stimuli, and targeting ability can be used as wall materials for oral colon-targeted delivery of polyphenols in nutrition intervention of IBD. This manuscript reviewed the latest progress in the design, preparation, and characterization of marine polysaccharides-derived multifunctional nanocarriers for polyphenol colon delivery. Chitosan, sodium alginate, chondroitin sulfate, and hyaluronic acid were discussed in the preparation of polyphenol delivery systems. The design strategy, synthesis methods, and structure characterization of multifunctional polyphenol carriers including stimuli-responsive nanocarriers, mucoadhesive and mucus-penetrating nanocarriers, colon targeted nanocarriers, and bioactive compounds codelivery nanocarriers were reviewed in the alleviation of IBD. The research perspectives in the preparation and characterization of delivery carriers using marine polysaccharide as materials were proposed for their potential application in food bioactive components.

Alginate-Based Smart Materials and Their Application: Recent Advances and Perspectives

Nature produces materials using available molecular building blocks following a bottom-up approach. These materials are formed with great precision and flexibility in a controlled manner. This approach offers the inspiration for manufacturing new artificial materials and devices. Synthetic artificial materials can find many important applications ranging from personalized therapeutics to solutions for environmental problems. Among these materials, responsive synthetic materials are capable of changing their structure and/or properties in response to external stimuli, and hence are termed "smart" materials. Herein, this review focuses on alginate-based smart materials and their stimuli-responsive preparation, fragmentation, and applications in diverse fields from drug delivery and tissue engineering to water purification and environmental remediation. In the first part of this report, we review stimuli-induced preparation of alginate-based materials. Stimuli-triggered decomposition of alginate materials in a controlled fashion is documented in the second part, followed by the application of smart alginate materials in diverse fields. Because of their biocompatibility, easy accessibility, and simple techniques of material formation, alginates can provide solutions for several present and future problems of humankind. However, new research is needed for novel alginate-based materials with new functionalities and well-defined properties for targeted applications.

Biomolecule Release from Alginate Composite Hydrogels Triggered by Logically Processed Signals

Alginate composite hydrogels that exhibit highly sensitive stimuli-responsive behavior were used for signal-stimulated release of pre-loaded insulin. The alginate pores, particularly located at the periphery, were blocked by interpenetration of polyvinyl alcohol (PVA) cross-linked with 1,3-benzenediboronic acid (IPN), thus, significantly reducing uncontrolled leakage of the entrapped biomolecules. The beads were loaded with insulin and various enzymes mimicking different Boolean logic gates (AND, OR, NOR, IMP, INHIB). The enzymes were activated with biologically relevant input signals applied in four logic combinations: 0,0; 1,0; 0,1; 1,1, having the production of H₂ O₂ as the result of the biocatalytic reactions. The "successful" combination of the input signals leading to the H₂ O₂ production was different for different logic gates, following the corresponding truth tables of the logic gates. When H₂ O₂ was produced, boronate ester bonds were oxidized and the IPN was irreversibly degraded, thus re-opening the original pores of the hydrogel. This process allowed release of insulin from the alginate beads. The smart soft material that we have developed tackled well-known limitations of these systems and it may prove valuable in future medical diagnostics or treatments.

A Critical Review on the Synthesis of Natural Sodium Alginate Based Composite Materials: An Innovative Biological Polymer for Biomedical Delivery Applications

Sodium alginate (Na-Alg) is water-soluble, neutral, and linear polysaccharide. It is the derivative of alginic acid which comprises 1,4-β-d-mannuronic (M) and α-l-guluronic (G) acids and has the chemical formula (NaC6H7O6). It shows water-soluble, non-toxic, biocompatible, biodegradable, and non-immunogenic properties. It had been used for various biomedical applications, among which the most promising are drug delivery, gene delivery, wound dressing, and wound healing. For different biomedical applications, it is used in different forms with the help of new techniques. That is the reason it had been blended with different polymers. In this review article, we present a comprehensive overview of the combinations of sodium alginate with natural and synthetic polymers and their biomedical applications involving delivery systems. All the scientific/technical issues have been addressed, and we have highlighted the recent advancements.

Self-powered molecule release systems activated with chemical signals processed through reconfigurable Implication or Inhibition Boolean logic gates

The Implication (IMPLY) and Inhibition (INHIB) Boolean logic gates were realized using switchable chimeric pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH-Clamp) containing a fused affinity clamp unit recognizing a signal-peptide. The second component of the logic gate was the wild-type PQQ-glucose dehydrogenase working cooperatively with the PQQ-GDH-Clamp enzyme. The IMPLY and INHIB gates were realized using the same enzyme composition activated with differently defined input signals, thus representing reconfigurable logic systems. The logic gates were first tested while operating in a solution with optical analysis of the output signals. Then, the enzymes were immobilized on a buckypaper electrode for electrochemical transduction of the output signals. The switchable modified electrodes mimicking the IMPLY or INHIB logic gates were integrated with an oxygen-reducing electrode modified with bilirubin oxidase to operate as a biofuel cell activated/inhibited by various input signal combinations processed either by IMPLY or INHIB logic gates. The switchable biofuel cell was used as a self-powered device triggering molecule release function controlled by the logically processed molecule signals.

Electrophoretic deposition of polymers and proteins for biomedical applications

This review is focused on new electrophoretic deposition (EPD) mechanisms for deposition biomacromolecules, such as biopolymers, proteins and enzymes. Among the rich literature sources of EPD of biopolymers, proteins and enzymes for biomedical applications we selected papers describing new fundamental deposition mechanisms. Such deposition mechanisms are of critical importance for further development of EPD method and its emerging biomedical applications. Our goal is to emphasize innovative ideas which have enriched colloid and interface science of EPD during recent years. We describe various mechanisms of cathodic and anodic EPD of charged biopolymers. Special attention is focused on in-situ chemical modification of biopolymers and crosslinking techniques. Recent innovations in the development of natural and biocompatible charged surfactants and film forming agents are outlined. Among the important advances in this area are the applications of bile acids and salts for EPD of neutral polymers. Such innovations allowed for the successful EPD of various electrically neutral functional polymers for biomedical applications. Particularly important are biosurfactant-polymer interactions, which facilitate dissolution, dispersion, charging, electrophoretic transport and deposit formation. Recent advances in EPD mechanisms addressed the problem of EPD of proteins and enzymes related to their charge reversal at the electrode surface. Conceptually new methods are described, which are based on the use of biopolymer complexes with metal ions, proteins, enzymes and other biomolecules. This review describes new developments in co-deposition of biomacromolecules and future trends in the development of new EPD mechanisms and strategies for biomedical applications.

Construction and research on size and phase 'fixed-point remodelling' intelligent drug delivery system

It is important to enhance penetration depth of nanomedicine and realise rapid drug release simultaneously at targeted tumour for improving anti-tumour efficiency of chemotherapeutic drugs. This project employed sodium alginate (Alg) as matrix material, to establish tumour-responsive nanogels with particle size conversion and drug controlled release functions. Specifically, tumour-targeting peptide CRGDK was conjugated with Alg first (CRGDK-Alg). Then, doxorubicin (DOX) was efficiently encapsulated in CRGDK-FeAlg nanogel during the cross-linking process (CRGDK-FeAlg/DOX). This system was closed during circulation. Once reaching tumour, the particle size of nanogels was reduced to ∼25 nm, which facilitated deep penetration of DOX in tumour tissues. After entering tumour cells, the size of nanogels was further reduced to ∼10 nm and DOX was released simultaneously. Meanwhile, FeAlg efficiently catalysed H₂O₂ to produce •OH by Fenton reaction, achieving local chemodynamic therapy without O₂ mediation. Results showed CRGDK-FeAlg/DOX significantly inhibited tumour proliferation in vivo with V/V0 of 1.13 after treatment, significantly lower than that of control group with V/V0 of 4.79.

Design of injectable hydrogels of gelatin and alginate with ferric ions for cell transplantation

The objective of this study is to design bioabsorbable injectable hydrogels based on the physico-chemical interaction between biocompatible polymers and ferric ions, and evaluate the survival, proliferation, and osteogenic differentiation of cells encapsulated in the hydrogels. The injectable hydrogels were prepared by simply mixing mixed alginate/gelatin solution at various ratios and FeCl₃ solution. The hydrogels prepared disappeared within a few days in the phosphate buffered-saline solution (PBS) with containing collagenase although the disappearance rate increased with an increase of the gelatin ratio in the hydrogel. For the hydrogel of alginate/gelatin low ratio, the survival and proliferation of cells in the hydrogel-encapsulated condition were significantly high compared with those of hydrogel at the higher ratios. The cells collected 3 days after cultured in the hydrogel also proliferated to a significantly higher extent than those collected from other hydrogels. The proliferation ability of cells was similar that of cells cultured on the standard tissue culture polystyrene (TCPS) dish. When evaluated to compare with cells cultured on the TCPS dish, the expression of runt-related transcription factor-2 (RUNX2) gene, the alkaline phosphatase (ALP) activity, and the calcium precipitation were significantly high. The cells were encapsulated by the mixed alginate/gelatin and FeCl₃ hydrogel and injected in the back subcutis of mice, the percentage of cells retained in the injected site was higher than that of cells injected in the PBS suspension. It is concluded that the injectable hydrogel prepared by simple mixing mixed alginate/gelatin solution and FeCl₃ solution is a promising material for the cell transplantation. STATEMENT OF SIGNIFICANCE: Injectable hydrogels prepared by simple mixing mixed alginate/gelatin solution at various ratios and FeCl₃ solution. For the hydrogel of alginate/gelatin low ratio, the survival, the proliferation, and the differentiate properties of cells in the hydrogel-encapsulated condition were similar those of cells cultured on the TCPS dish. When the cells encapsulated hydrogels were injected in the back subcutis of mice, the percentage of cells retained in the injected site was higher than that of cells injected in the PBS suspension. It is concluded that the present injectable hydrogel is a promising material for the cell transplantation.

Not-XOR (NXOR) Logic Gate Realized with Enzyme-Catalyzed Reactions: Optical and Electrochemical Signal Transduction

The studied enzyme-based biocatalytic system mimics NXOR Boolean logic gate, which is a logical operator that corresponds to equality in Boolean algebra. It gives the functional value true (1) if both functional arguments (input signals) have the same logical value (0,0 or 1,1), and false (0) if they are different (0,1 or 1,0). The output signal producing reaction is catalyzed by pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH), which is inhibited at acidic and basic pH values. Two other reactions catalyzed by esterase and urease produce acetic acid and ammonium hydroxide, respectively, shifting solution pH from the optimum pH for PQQ-GDH to acidic and basic values (1,0 and 0,1 input combinations, respectively), thus switching the enzyme activity off (output 0). When the input signals are not applied (0,0 combination) or both applied compensating each other (1,1 combination) the optimum pH is preserved, thus keeping PQQ-GDH running at the high rate (output 1). The biocatalytic cascade mimicking the NXOR gate was characterized optically and electrochemically. In the electrochemical experiments the PQQ-GDH enzyme communicated electronically with a conducting electrode support, thus resulting in the electrocatalytic current when signal combinations 0,0 and 1,1 were applied. The logic gate operation, when it was realized electrochemically, was also extended to the biomolecular release controlled by the gate. The release system included two electrodes, one performing the NXOR gate and another one activated for the release upon electrochemically stimulated alginate hydrogel dissolution. The studied system represents a general approach to the biocatalytic realization of the NXOR logic gate, which can be included in different catalytic cascades mimicking operation of concatenated gates in sophisticated logic circuitries.

Experimental Realization of a High-Quality Biochemical XOR Gate

We report an experimental realization of a biochemical XOR gate function that avoids many of the pitfalls of earlier realizations based on biocatalytic cascades. Inputs-represented by pairs of chemicals-cross-react to largely cancel out when both are nearly equal. The cross-reaction can be designed to also optimize gate functioning for noise handling. When not equal, the residual inputs are further processed to result in the output of the XOR type, by biocatalytic steps that allow for further gate-function optimization. The quality of the realized XOR gate is theoretically analyzed.