Great effort has been devoted to engineering Saccharomyces cerevisiae with pentose metabolism through the oxido-reductase pathway for cellulosic ethanol production, but intrinsic cofactor imbalance ...is observed, which substantially compromises ethanol yield. Zymomonas mobilis not only can be engineered for pentose metabolism through the isomerase pathway without cofactor imbalance but also metabolizes sugar through the Entner–Doudoroff pathway with less ATP and biomass produced for more sugar to be used for ethanol production. Moreover, the availabilities of genome sequence information for multiple Z. mobilis strains and advanced genetics tools have laid a solid foundation for engineering this species, and the self-flocculation of the bacterial cells also presents significant advantages for bioprocess engineering. Here, we highlight some of recent advances in these aspects.
Zymomonas mobilis metabolizes glucose through the Entner–Doudoroff (ED) pathway, with less ATP generated and biomass accumulated for more ethanol production.
The large specific cell surface of Z. mobilis together with the ED pathway facilitates glucose uptake and ethanol fermentation.
Its metabolic characteristics and narrow substrate spectrum make Z. mobilis unsuitable for fuel ethanol production from sugar- and starch-based feedstocks, but it would be a good host to be engineered for cellulosic ethanol production.
When self-flocculated, Z. mobilis can be immobilized within fermenters for high cell density to improve ethanol productivity. Meanwhile, its tolerance to environmental stresses may be enhanced by this morphological change.
Both Z. mobilis ZM4 and its self-flocculating mutant ZM401 can tolerate more than 100g/L ethanol, which is sufficient for cellulosic ethanol production.
The slow rate of extracellular electron transfer (EET) of electroactive microorganisms remains a primary bottleneck that restricts the practical applications of bioelectrochemical systems. ...Intracellular NAD(H/
) (i.e., the total level of NADH and NAD
) is a crucial source of the intracellular electron pool from which intracellular electrons are transferred to extracellular electron acceptors via EET pathways. However, how the total level of intracellular NAD(H/
) impacts the EET rate in Shewanella oneidensis has not been established. Here, we use a modular synthetic biology strategy to redirect metabolic flux towards NAD
biosynthesis via three modules: de novo, salvage, and universal biosynthesis modules in S. oneidensis MR-1. The results demonstrate that an increase in intracellular NAD(H/
) results in the transfer of more electrons from the increased oxidation of the electron donor to the EET pathways of S. oneidensis, thereby enhancing intracellular electron flux and the EET rate.
Rational design and controllable synthesis of well‐defined nanostructures with high stability and Pt‐like activity for hydrogen evolution reaction (HER) are critical for renewable energy conversion. ...Herein, a unique pyrolysis strategy is demonstrated for the synthesis of RhPx nanoparticles (NPs) in N, P co‐doped thin carbon nanoshells (RhPx@NPC nanoshells) that display high electrocatalytic activity and stability over a wide pH range. This strategy involves simultaneous phosphorization and pyrolysis processes that can produce highly‐dispersed RhPx NPs within N, P co‐doped carbon nanoshells and at the same time induce thinning of carbon nanoshells from inside out. The resulting RhPx@NPC nanoshells not only possess Pt‐like activity for HER with low overpotentials to achieve 10 mA cm−2 (22 mV in 0.5 m H2SO4, 69 mV in 1.0 m KOH, and 38 mV in 1.0 m phosphate buffered saline (PBS)) but also provide long‐term durability in a wide pH range. The remarkable HER performance of RhPx@NPC nanoshells is ascribed to the high surface area, abundant mesoporosity, strong catalyst–support interaction, ultrathin carbon encapsulation, and N, P co‐doping. This work provides an effective strategy for designing heterostructured electrocatalysts with high catalytic activity and stability desired for reactions that may occur under harsh conditions.
A unique pyrolysis strategy is demonstrated for the synthesis of RhPx nanoparticles in N, P co‐doped carbon nanoshells that display high electrocatalytic activity and stability over a wide pH range. This strategy involves simultaneous phosphorization and pyrolysis processes that can produce highly dispersed RhPx nanoparticles within carbon nanoshells and induce thinning of carbon nanoshells from the inside out.
Lignocellulosic biomass is a sustainable feedstock for fuel ethanol production, but it is characterized by low mass and energy densities, and distributed production with relatively small scales is ...more suitable for cellulosic ethanol, which can better balance cost for the feedstock logistics. Lignocellulosic biomass is recalcitrant to degradation, and pretreatment is needed, but more efficient pretreatment technologies should be developed based on an in-depth understanding of its biosynthesis and regulation for engineering plant cell walls with less recalcitrance. Simultaneous saccharification and co-fermentation has been developed for cellulosic ethanol production, but the concept has been mistakenly defined, since the saccharification and co-fermentation are by no means simultaneous. Lignin is unreactive, which not only occupies reactor spaces during the enzymatic hydrolysis of the cellulose component and ethanol fermentation thereafter, but also requires extra mixing, making high solid loading difficult for lignocellulosic biomass and ethanol titers substantially compromised, which consequently increases energy consumption for ethanol distillation and stillage discharge, presenting another challenge for cellulosic ethanol production. Pentose sugars released from the hydrolysis of hemicelluloses are not fermentable with Saccharomyces cerevisiae used for ethanol production from sugar- and starch-based feedstocks, and engineering the brewing yeast and other ethanologenic species such as Zymomonas mobilis with pentose metabolism has been performed within the past decades. However strategies for the simultaneous co-fermentation of pentose and hexose sugars that have been pursued overwhelmingly for strain development might be modified for robust ethanol production. Finally, unit integration and system optimization are needed to maximize economic and environmental benefits for cellulosic ethanol production. In this article, we critically reviewed updated progress, and highlighted challenges and strategies for solutions.
Microscale cell carriers have recently garnered enormous interest in repairing tissue defects by avoiding substantial open surgeries using implants for tissue regeneration. In this study, the highly ...open porous microspheres (HOPMs) are fabricated using a microfluidic technique for harboring proliferating skeletal myoblasts and evaluating their feasibility toward cell delivery application in situ. These biocompatible HOPMs with particle sizes of 280–370 µm possess open pores of 10–80 µm and interconnected paths. Such structure of the HOPMs conveniently provide a favorable microenvironment, where the cells are closely arranged in elongated shapes with the deposited extracellular matrix, facilitating cell adhesion and proliferation, as well as augmented myogenic differentiation. Furthermore, in vivo results in mice confirm improved cell retention and vascularization, as well as partial myoblast differentiation. These modular cell‐laden microcarriers potentially allow for in situ tissue construction after minimally invasive delivery providing a convenient means for regeneration medicine.
Highly open porous microspheres (HOPMs) are conveniently designed using a microfluidic setup and evaluated for their feasibility toward minimally invasive cell delivery‐based tissue regeneration. These biocompatible HOPMs with interconnected paths facilitate a high cell proliferation rate, and partial differentiation of skeletal myoblasts. These modular cells‐laden microcarriers provide a convenient means for in situ repair of tissue defects and applications in regenerative medicine.
Display omitted
Developing transition metal-based electrocatalysts with rich active sites for water electrolysis plays important roles in renewable energy fields. So far, some strategies including ...designing nanostructures, incorporating conductive support or foreign elements have been adopted to develop efficient electrocatalysts. Herein, we summarize recent progresses and propose in-situ electrochemical activation as a new pretreating technique for enhanced catalytic performances. The activation techniques mainly comprise facile electrochemical processes such as anodic oxidation, cathodic reduction, etching, lithium-assisted tuning and counter electrode electro-dissolution. During these electrochemical treatments, the catalyst surfaces are modified from bulk phase, which can tune local electronic structures, create more active species, enlarge surface area and thus improve the catalytic performances. Meanwhile, this technique can couple the atomic, electronic structures with electrocatalysis mechanisms for water splitting. Compared to traditional chemical treatment, the in-situ electrochemical activation techniques have superior advantages such as facile operation, mild environment, variable control, high efficiency and flexibility. This review may provide guidance for improving water electrolysis efficiencies and hold promising for application in many other energy-conversion fields such as supercapacitors, fuel cells and batteries.
Despite their advantageous morphological attributes and attractive physicochemical properties, mesoporous silica nanoparticles (MSNs) are merely supported as carriers or vectors for a reason. ...Incorporating various metal species in the confined nanospaces of MSNs (M‐MSNs) significantly enriches their mesoporous architecture and diverse functionalities, bringing exciting potentials to this burgeoning field of research. These incorporated guest species offer enormous benefits to the MSN hosts concerning the reduction of their eventual size and the enhancement of their performance and stability, among other benefits. Substantially, the guest species act through contributing to reduced aggregation, augmented durability, ease of long‐term storage, and reduced toxicity, attributes that are of particular interest in diverse fields of biomedicine. In this review, the first aim is to discuss the current advancements and latest breakthroughs in the fabrication of M‐MSNs, emphasizing the pros and cons, the confinement of various metal species in the nanospaces of MSNs, and various factors influencing the encapsulation of metal species in MSNs. Further, an emphasis on potential applications of M‐MSNs in various fields, including in adsorption, catalysis, photoluminescence, and biomedicine, among others, along with a set of examples is provided. Finally, the advances in M‐MSNs with perspectives are summarized.
Despite their captivating physicochemical properties, mesoporous silica nanoparticles are only supported as carriers. To enrich their performance, various metal species are encapsulated in their nanospaces for diverse functionalities. This review provides an overview highlighting the attractive features of these innovative constructs and a synopsis of the current advancements and latest breakthroughs in their potential catalytic and various biomedical applications.
Biodegradable nanoparticles (NPs) have been frequently used as insulin transdermal delivery vehicles due to their grand bioavailability, better encapsulation, controlled release and less toxic ...properties. However, the skin's barrier properties prevent insulin-loaded NP permeation at useful levels. Nowadays, microneedles have been spotlighted as novel transdermal delivery systems due to their advantages such as painlessness, efficient penetration and no hazardous residues. Herein, we introduce polymeric nanocarriers based on carboxymethyl chitosan (CMCS) for insulin delivery, combining with microneedle therapy systems, which can rapidly deliver insulin (INS) into the skin. The resulting CMCS-based nanocarriers are spherical nanoparticles with a mean size around 200 nm, which could generate supramolecular micelles to effectively encapsulate insulin (EE% = 83.78 ± 3.73%). A nanocrystalline microneedle array (6 × 6, 75/150 μm) was used to penetrate the stratum corneum (SC) for enhancing transdermal insulin delivery, while minimizing the pain sensation caused by intravenous injection. Compared with the transdermal rate of passive diffusion 2.77 ± 0.64 μg (cm
−2
h
−1
), the transdermal rate of the insulin-loaded NP combined with microneedle penetration shows a 4.2-fold increase 10.24 ± 1.06 μg (cm
−2
h
−1
) from permeation experiment
in vitro
.
In vivo
hypoglycemic experiments demonstrate the potential of using nanocarrier combination with microneedle arrays for painless insulin delivery through the skin in a clinical setting. Thus, the developed combination scheme of nanoparticles and microneedle arrays offers an effective, user-friendly, and low-toxicity option for diabetes patients requiring long-term and multiple treatments.
Biodegradable nanoparticles (NPs) have been frequently used as insulin transdermal delivery vehicles due to their grand bioavailability, better encapsulation, controlled release and less toxic properties.
NiSe@NiOOH core–shell hyacinth-like nanostructures supported on nickel foam (NF) have been successfully synthesized by a facile solvothermal selenization and subsequent in situ electrochemical ...oxidation (ISEO). First, the unique NiSe/NF nanopillar arrays were prepared in N,N-dimethylformamide (DMF) as a precursor template that can provide a large surface area, excellent conductivity, and robust support. Next, amorphous NiOOH covering the surface of NiSe nanopillars was fabricated by ISEO, as confirmed by XPS andEDX spectroscopy. SEM images revealed the hyacinth-like morphology of NiSe@NiOOH/NF with NiOOH as the shell and NiSe as the core. The electrochemical performance of NiSe@NiOOH/NF for the oxygen evolution reaction (OER) was investigated. NiSe@NiOOH/NF demonstrates an obviously enhanced OER activity with much lower overpotential of 332 mV at 50 mA cm–2 compared to other Ni-based electrocatalysts. The low charge-transfer resistance (R ct), large electrochemical double-layer capacitance (C dl) of electrochemically active surface areas (ECSAs), and excellent long-term stability of NiSe@NiOOH/NF confirm the enhancement of its electrochemical performance for the OER, which can be ascribed to the large amount of active sites derived from the amorphous NiOOH shell and the good conductivity and stability derived from the NiSe core. In addition, the synergistic effect between the NiSe core and NiOOH shell could serve for a highly efficient OER electrocatalyst.
This article demonstrates the fabrication of versatile nanoformulation by conveniently wrapping the ultrasmall platinum nanoparticles-dispersed over the zinc metal species-doped mesoporous ...silica-based nanocarriers (Zn-MSNs). Such innovative nanocarriers not only convey the drug cargo efficiently but also facilitate the advanced abilities of deep tumor penetration through interacting with adherens junctions and aphotic (dark) synergistic therapeutic effects to combat cancer multidrug resistance.
Display omitted
•Ultrasmall Pt-NPs were wrapped over metal-doped MSNs to combat cancer MDR.•Pt-NPs facilitated advanced abilities of deep tumor penetration and aphotic synergistic effects.•Pt-NPs have shown significant effect on integrity of adherens junctions between cells.•Zn species offered pH-responsive coordination with Dox enabling its precise release.•ROS from Dox enabled the conversion to Pt ions, resulting in synergistic tumor ablation.
Despite the significant advancements in the development of a wide-variety of nanocarriers-based delivery systems for cancer therapy, several predominant issues remain unaddressed such as active combat of cancer multidrug resistance (MDR) and the limited penetration efficacy of the delivery systems. To address these issues, herein, we demonstrate the fabrication of a versatile nanoformulation by conveniently wrapping the ultrasmall platinum (Pt) nanoparticles-dispersed chitosan (CS) over the zinc-doped mesoporous silica nanocarriers (Zn-MSNs) through a facile, yet efficient self-assembly approach. These versatile nanocomposites decorated with highly active, ultrasmall Pt nanoparticles potentially facilitate the advanced therapeutic abilities of deep tumor penetration and aphotic (dark) synergistic ablation of the MDR tumors effectively. In this framework, pericellular actin staining results confirmed the effect of decorated Pt species on the integrity of the adherens junctions between cells. Remarkably, the Zn species that are doped in the siliceous frameworks substantially enhanced the loading efficiency of doxorubicin (Dox) molecules without any additional functionalization and facilitated the augmented anticancer efficacy by delivering them precisely in the tumor’s acidic microenvironment through specifically dismantling the established coordination interactions between the host and guest species. Further, the resultant free radical species from the delivered Dox species intracellularly enabled the catalytic conversion of the Pt nanoparticles to their corresponding divalent ionic species, which synergistically participated in the tumor ablation. These consequences of Pt species toward synergistic ablation of MDR cells happened to be favourable only in the presence of Dox species, a free radical generator. In vitro and in vivo investigations confirm augmented antiproliferation and synergistic inhibition effects of designed nanocomposites in the MDR tumors. These nanocomposites decorated with highly active Pt nanoparticles potentially allow for deep tumor penetration and synergistic ablation of the tumor by conveniently combating the MDR efficaciously.
PDF
