Microenvironmental pH Research Articles

Fabrication and evaluation of a portable and reproducible quartz crystal microbalance immunochip for label-free detection of β-lactoglobulin allergen in milk products

In this study, a label-free, portable and reproducible immunochip based on quartz crystal microbalance (QCM) was developed for the qualitative detection of β-lactoglobulin (β-LG), an allergen, in milk products. Experimental parameters in the fabrication and regeneration procedure such as pH of the coupling microenvironment, amount of anti-β-LG antibody and regeneration reagent were optimized in detail. Under optimal conditions, the proposed QCM immunochip exhibited good recognition of β-LG, with a calibration curve of ΔF = 12.877Cβ-LG0.4809 (R2 = 0.9982) and limit of detection of 0.04 μg/mL. Additionally, this portable QCM immunochip had good stability, high specificity, and no obvious cross-reaction to three other milk proteins (α-casein, α-lactalbumin, and lactoferrin). It could compete a qualitative measurement within 5 min, and could be reused at least ten times. In the β-LG analysis of actual milk samples, the developed QCM immunochip yielded reliable and accurate results, which correlated strongly with those from the standard HPLC method (R2 = 0.9969). Thus, the portable, stable, and reproducible QCM immunochip developed in this study allowed the rapid, cost-effectively and sensitively measure the β-LG in milk products.

Beyond the Dilemmas: Design of PLA-PEG Assemblies Based on pH-Reversible Boronic Ester for the Synchronous PEG De-Shielding and Ligand Presentation to Hepatocytes

A new polymeric construct is proposed as a starting material for a liver-targeted delivery system in the present communication. The polymeric material has been designed to be sensitive to pH variations and potentially loaded with hydrophobic antitumoral agents. It is based on one of the most used copolymers in the field of nanomedicine: PEG-PLA. The latter, usually obtained by polymerization of lactic acid on the hydroxyl-terminated polyether, is assembled by the pH-reversible condensation between a phenylboronic acid-ended methoxy PEG 2000 (MeO-PEG2000-PBA) and a galactose-capped PLA of 1–10 kDa (PLA-Gal). Our approach is based on the strategic assumption that would allow a new ligand presentation strategy in which Gal is both a structural element for the stimulus-responsive PEG de-shielding and the targeting moiety. Indeed, Gal has a vicinal diol able to form a reversible boronate ester with a B(OH) 2 residue, which is cleavable at the acidic pH of the tumor microenvironment, and it is also recognized by the asialoglycoprotein receptor, which is hyper-expressed on the membrane of hepatocytes. The functionalization of the two blocks is presented here, and they are characterized using NMR, FTIR, and GPC. The analytical evaluation of the ability of the boronated PEG and Gal to condense in a pH sensible way completes the study.

In Vitro and In Vivo Anticancer and Genotoxicity Profiles of Green Synthesized and Chemically Synthesized Silver Nanoparticles.

Silver nanoparticles were green synthesized (Ag-PTs) employing the crude extract of Padina tetrastromatica, a marine alga, and their anticancer and safety profile were compared with those of chemically synthesized silver nanoparticles (Ag-NPs) by in vitro and in vivo models. Ag-PT exhibited potent cytotoxicity against B16-F10 (IC50 = 3.29), MCF-7 (IC50 = 4.36), HEPG2 (IC50 =3.89), and HeLa (IC50 = 4.97) cancer cell lines, whereas they exhibited lower toxicity on normal CHO-K1 cells (IC50 = 5.16). The potent anticancer activity of Ag-PTs on cancer cells is due to the liberation of ions from the nanoparticles. Increased ion internalization to the cells promotes reactive oxygen species (ROS) production and ultimately leads to cell death. The in vitro anticancer results and in vivo melanoma tumor regression study showed significant inhibition of melanoma tumor growth due to Ag-PT treatment. Ag-PT is involved in the upregulation of the p53 protein and downregulation of Sox-2 along with the Ki-67 protein. The antitumor effects of Ag-PTs may be due to the additional release of ions at a lower pH of the tumor microenvironment than that of the normal tissue. The results of safety investigations of Ag-PT by studying mitotic chromosome aberrations (CAs), micronucleus (MN) induction, and mitotic index (MI) demonstrated Ag-PT to be less genotoxic compared to Ag-NP. The bioefficacy and toxicology outcomes together demonstrated that the green synthesized silver nanoparticles (Ag-PTs) could be explored to develop a biocompatible, therapeutic agent and a vehicle of drug delivery for various biomedical applications.

Double-activation of mitochondrial permeability transition pore opening via calcium overload and reactive oxygen species for cancer therapy

BackgroundCalcium ions (Ca2+) participates in various intracellular signal cascades and especially plays a key role in pathways relevant to cancer cells. Mitochondrial metabolism stimulated by calcium overload can trigger the opening of the mitochondrial permeability transition pore (MPTP), which leads to cancer cell death.MethodsHerein, a mitochondrial pathway for tumour growth inhibition was built via the double-activation of MPTP channel. Fe2+ doped covalent organic frameworks (COF) was synthesised and applied as template to grow CaCO3 shell. Then O2 was storaged into Fe2+ doped COF, forming O2-FeCOF@CaCO3 nanocomposite. After modification with folic acid (FA), O2-FeCOF@CaCO3@FA (OFCCF) can target breast cancer cells and realize PDT/Ca2+ overload synergistic treatment.ResultsCOF can induce the production of 1O2 under 650 nm irradiation for photodynamic therapy (PDT). Low pH and hypoxia in tumour microenvironment (TME) can activate the nanocomposite to release oxygen and Ca2+. The released O2 can alleviate hypoxia in TME, thus enhancing the efficiency of COF-mediated PDT. Abundant Ca2+ were released and accumulated in cancer cells, resulting in Ca2+ overload. Notably, the reactive oxygen species (ROS) and Ca2+ overload ensure the sustained opening of MPTP, which leads to the change of mitochondria transmembrane potential, the release of cytochrome c (Cyt c) and the activation of caspases 3 for cancer cell apoptosis.ConclusionThis multifunctional nanosystem with TME responded abilities provided a novel strategy for innovative clinical cancer therapy.Graphical

Hydroxyapatite nanoparticles promote mitochondrial-based pyroptosis via activating calcium homeostasis and redox imbalance in vascular smooth muscle cells

Hydroxyapatite nanoparticles (HAP) have been widely used in various fields because of their natural biological origin and functional properties. The emerging evidence on their toxicities has attracted research interest. HAP-induced vascular smooth muscle cell (VSMC) damage is a key step in vascular calcification (VC), particularly in patients with chronic kidney disease. However, the injury effects and mechanism of action of HAP on VSMCs have not been extensively investigated. This study comprehensively characterized commercially available HAP and investigated its adverse biological effects in cultured A7R5 cells. In vitro experiments revealed that internalized HAP was localized in lysosomes, followed by the release of Ca2+ owing to the low pH microenvironment. Upon Ca2+ homeostasis, Ca2+ enters the mitochondria, leading to the simultaneous generation of reactive oxygen species (ROS). ROS subsequently attack mitochondrial transmembrane potentials, promote mitochondrial ROS production, and oxidize mitochondrial DNA (Ox-mtDNA). Mitochondrial permeability-transition pores open, followed by the release of more Ox-mtDNA from the mitochondria into the cytosol due to the redox imbalance. This activates NLRP3/caspase-1/gasdermin D-dependent pyroptosis and finally excretes inflammatory factors to induce VC; an antioxidant could rescue this process. It has been suggested that HAP could induce an imbalance in intracellular Ca2+ homeostasis in A7R5 cells, followed by the promotion of mitochondrial dysfunction and cell pyroptosis, finally enhancing VC. To detect the in vivo toxicity of HAP, mice were treated with Cy7-labelled HAP NPs for 24 h. In vivo results also demonstrated that HAP accumulated in the kidneys, accompined with increased Ca concentration, upregulated oxidative stress-related factor and kidney damage. Overall, our research elucidates the mechanism of calcium homeostasis and redox imbalance, providing insights into the prevention of HAP-induced cell death.

Identification of distinct slow mode of reversible adaptation of pancreatic ductal adenocarcinoma to the prolonged acidic pH microenvironment

BackgroundPancreatic ductal adenocarcinoma (PDAC) is the most common pancreatic neoplasm with high metastatic potential and poor clinical outcome. Like other solid tumors, PDAC in the early stages is often asymptomatic, and grows very slowly under a distinct acidic pHe (extracellular pH) microenvironment. However, most previous studies have only reported the fate of cancerous cells upon cursory exposure to acidic pHe conditions. Little is known about how solid tumors—such as the lethal PDAC originating within the pancreatic duct-acinar system that secretes alkaline fluids—evolve to withstand and adapt to the prolonged acidotic microenvironmental stress.MethodsRepresentative PDAC cells were exposed to various biologically relevant periods of extracellular acidity. The time effects of acidic pHe stress were determined with respect to tumor cell proliferation, phenotypic regulation, autophagic control, metabolic plasticity, mitochondrial network dynamics, and metastatic potentials.ResultsUnlike previous short-term analyses, we found that the acidosis-mediated autophagy occurred mainly as an early stress response but not for later adaptation to microenvironmental acidification. Rather, PDAC cells use a distinct and lengthy process of reversible adaptive plasticity centered on the early fast and later slow mitochondrial network dynamics and metabolic adjustment. This regulates their acute responses and chronic adaptations to the acidic pHe microenvironment. A more malignant state with increased migratory and invasive potentials in long-term acidosis-adapted PDAC cells was obtained with key regulatory molecules being closely related to overall patient survival. Finally, the identification of 34 acidic pHe-related genes could be potential targets for the development of diagnosis and treatment against PDAC.ConclusionsOur study offers a novel mechanism of early rapid response and late reversible adaptation of PDAC cells to the stress of extracellular acidosis. The presence of this distinctive yet slow mode of machinery fills an important knowledge gap in how solid tumor cells sense, respond, reprogram, and ultimately adapt to the persistent microenvironmental acidification.

Tumor intracellular microenvironment-responsive nanoparticles for magnetically targeted chemotherapy

Nanoparticles (NPs) with responsive modalities in biological microenvironments and external stimuli have received great attention as highly efficient and precise cancer therapy agents. In this study, tumor intracellular microenvironment-responsive NPs co-assembled from poly(ethylene glycol)-poly(aspartic acid) [PEG-P(Asp)] copolymer, doxorubicin (DOX), and superparamagnetic iron oxide NPs (SPIONs), termed as PEG-P(Asp)/DOX/SPIONs, were prepared for tumor intracellular microenvironment (enzyme and pH)-responsive and magnetically targeted chemotherapy. The NPs exhibited not only enzyme-responsive degradation in the presence of protease, but also triggered release of DOX at pH 5, which is an acidity similar to endolysosomal microenvironments in tumor cells. Furthermore, the PEG-P(Asp)/DOX/SPIONs showed a contrast effect in magnetic resonance imaging. In vitro viability assays showed that PEG-P(Asp)/DOX/SPIONs could effectively augment the cytocompatibility of DOX compared to free DOX without a change in magnetic forces. Fluorescence microscopy images indicated that the fabricated NPs efficiently increased the targeted uptake and release of DOX within cells. Overall, this hybrid NP system could be a favorable biomedical agent for effective tumor-targeted anti-cancer therapy.

Temperature and Tumor Microenvironment Dual Responsive Mesoporous Magnetic Nanospheres for Magnetothermal Effect-Induced Cancer Theranostics

Temperature and Tumor Microenvironment Dual Responsive Mesoporous Magnetic Nanospheres for Magnetothermal Effect-Induced Cancer Theranostics

PH-Responsive Polymer Nanomaterials for Tumor Therapy.

The complexity of the tumor microenvironment presents significant challenges to cancer therapy, while providing opportunities for targeted drug delivery. Using characteristic signals of the tumor microenvironment, various stimuli-responsive drug delivery systems can be constructed for targeted drug delivery to tumor sites. Among these, the pH is frequently utilized, owing to the pH of the tumor microenvironment being lower than that of blood and healthy tissues. pH-responsive polymer carriers can improve the efficiency of drug delivery in vivo, allow targeted drug delivery, and reduce adverse drug reactions, enabling multifunctional and personalized treatment. pH-responsive polymers have gained increasing interest due to their advantageous properties and potential for applicability in tumor therapy. In this review, recent advances in, and common applications of, pH-responsive polymer nanomaterials for drug delivery in cancer therapy are summarized, with a focus on the different types of pH-responsive polymers. Moreover, the challenges and future applications in this field are prospected.

PH/ROS dual-responsive supramolecular polypeptide prodrug nanomedicine based on host-guest recognition for cancer therapy

Supramolecular nanomedicine assembly combined with polypeptide prodrug could become a powerful strategy to minimize drug leakage in blood circulation and trigger sufficient drug release at tumor tissue. Here, we developed a charge-reversal amphiphilic pillar[5]arene-modified polypeptide (P5-PLL-DMA), and reactive oxygen species (ROS)-sensitive polypeptide prodrug (P-PLL-DOX) including a ROS-cleavable thioketal (TK) linker between doxorubicin (DOX) and poly(L-lysine) (PLL), which could assemble via pillar[5]arene host-guest recognition, and further encapsulate chlorin e6 (Ce6) to obtain a supramolecular polypeptide prodrug (SPP-DOX/Ce6). The chemical conjugation to load drugs of DOX and the negatively charge of SPP-DOX/Ce6 could prevent premature drug leakage, and reduce undesirable interaction with serum proteins to enhance stability under physiological conditions (pH 7.4). Simultaneously, the carried charge of SPP-DOX/Ce6 reversed from negative to positive could effectively enhance the cellular internalization for efficient DOX delivery under acidic tumor microenvironment (pH 6.5). Upon 660 nm near-infrared light (NIR) irradiation, the ROS generated by encapsulated Ce6 rapidly cleaved the TK linker to release activated DOX, inducing the tumor-specific drug delivery. This intelligent supramolecular polypeptide prodrug based on pillar[5]arene host-guest recognition represents new avenues to develop stimulus responsive prodrug for enhanced cancer therapy with minimized the side effect. Statement of significanceIn this work, a pH/ROS dual-sensitive supramolecular polypeptide prodrug (SPP-DOX/Ce6) was developed to minimize drug leakage in blood circulation and trigger sufficient drug release at tumor tissue. The chemical conjugation to load drugs of DOX via a ROS-cleavable thioketal (TK) linker and the distinctive charge-reversal capacity of SPP-DOX/Ce6 significantly enhances the stability under physiological conditions (pH 7.4), while facilitates cellular uptake at tumor site (pH 6.8). Upon 660 nm near-infrared light (NIR) irradiation, the ROS generated by encapsulated Ce6 induces the rapid cleavage of TK linker to release activated DOX, achieving a tumor-specific drug delivery. This intelligent supramolecular polypeptide prodrug SPP-DOX/Ce6 provides an effective strategy to construct stimulus responsive prodrug for enhanced cancer therapy.

An antibody Fc engineered for conditional antibody-dependent cellular cytotoxicity at the low tumor microenvironment pH

Despite the exquisite specificity and high affinity of antibody-based cancer therapies, treatment side effects can occur since the tumor-associated antigens targeted are also present on healthy cells. However, the low pH of the tumor microenvironment provides an opportunity to develop conditionally active antibodies with enhanced tumor specificity. Here, we engineered the human IgG1 Fc domain to enhance pH-selective binding to the receptor FcγRIIIa and subsequent antibody-dependent cellular cytotoxicity (ADCC). We displayed the Fc domain on the surface of mammalian cells and generated a site-directed library by altering Fc residues at the Fc–FcγRIIIa interface to support interactions with positively charged histidine residues. We then used a competitive staining and flow cytometric selection strategy to isolate Fc variants exhibiting reduced FcγRIIIa affinities at neutral pH, but physiological affinities at the tumor-typical pH 6.5. We demonstrate that antibodies composed of Fab arms binding the breast cell epithelial marker Her2 and the lead Fc variant, termed acid-Fc, exhibited an ∼2-fold pH-selectivity for FcγRIIIa binding based on the ratio of equilibrium dissociation constants Kd,7.4/Kd,6.5, due to a faster dissociation rate at pH 7.4. Finally, in vitro ADCC assays with human FcγRIIIa-positive natural killer and Her2-positive target cells demonstrated similar activities for anti-Her2 antibodies bearing the wild-type or acid-Fc at pH 6.5, but nearly 20-fold reduced ADCC for acid-Fc at pH 7.4, based on EC50 ratios. This work shows the promise of mammalian cell display for Fc engineering and the feasibility of pH-selective Fc activation to provide a second dimension of selective tumor cell targeting.

PH and the Breast Cancer Recurrent Mutation D538G Affect the Process of Activation of Estrogen Receptor α.

Estrogen receptor α (ERα) is a regulatory protein that can access a set of distinct structural configurations. ERα undergoes extensive remodeling as it interacts with different agonists and antagonists, as well as transcription activation and repression factors. Moreover, breast cancer tumors resistant to hormone therapy have been associated with the imbalance between the active and inactive ERα states. Cancer-activating mutations in ERα play a crucial role in this imbalance and can promote the progression of cancer. However, the rate of this progression can also be increased by dysregulated pH in the tumor microenvironment. Many molecular aspects of the process of activation of ERα that can be affected by these pH changes and mutations are still unclear. Thus, we applied computational and experimental techniques to explore the activation process dynamics of ER for environments with different pHs and in the presence of one of the most recurrent cancer-activating mutations, D538G. Our results indicated that the effect of the pH increase associated with the D538G mutation promoted a robust stabilization of the active state of ER. We were also able to determine the main protein regions that have the most potential to influence the activation process under different pH conditions, which may provide targets of future therapeutics for the treatment of hormone-resistant breast cancer tumors. Finally, the approach used here can be applied for proteins associated with the proliferation of other cancer types, which can also have their function affected by small pH changes.

Density Functional Theory Investigation of the Biocatalytic Mechanisms of pH-Driven Biomimetic Behavior in CeO2.

There is considerable interest in the pH-dependent, switchable, biocatalytic properties of cerium oxide (CeO2) nanoparticles in biomedicine, where these materials exhibit beneficial antioxidant activity against reactive oxygen species (ROS) at a basic physiological pH but cytotoxic prooxidant activity in an acidic cancer cell pH microenvironment. While the general characteristics of the role of oxygen vacancies are known, the mechanism of their action at the atomic scale under different pH conditions has yet to be elucidated. The present work applies density functional theory (DFT) calculations to interpret, at the atomic scale, the pH-induced behavior of the stable {111} surface of CeO2 containing oxygen vacancies. Analysis of the surface-adsorbed media species reveals the critical role of pH on the interaction between ROS (•O2- and H2O2) and the defective CeO2 {111} surface. Under basic conditions, the superoxide dismutase (SOD) and catalase (CAT) biomimetic reactions can be performed cyclically, scavenging and decomposing ROS to harmless products, making CeO2 an excellent antioxidant. However, under acidic conditions, the CAT biomimetic reaction is hindered owing to the limited reversibility of Ce3+ ↔ Ce4+ and formation ↔ annihilation of oxygen vacancies. A Fenton biomimetic reaction (H2O2 + Ce3+ → Ce4+ + OH- + •OH) is predicted to occur simultaneously with the SOD and CAT biomimetic reactions, resulting in the formation of hydroxyl radicals, making CeO2 a cytotoxic prooxidant.

Dual stimuli-responsive dendronized prodrug derived from poly(oligo-(ethylene glycol) methacrylate)-based copolymers for enhanced anti-cancer therapeutic effect

In this study, we developed an enzyme- and pH-responsive dendronized poly(oligo-(ethylene glycol) methacrylate) (pOEGMA)-doxorubicin (DOX) polymeric prodrug, which combined the pOEGMA structure with a degradable peptide dendron. The introduction of the dendron in the prodrug hindered the entanglement of brush oligo-(ethylene glycol) (OEG) chains, allowed the prodrug to possess dual stimuli-responsiveness, and mediated self-assembly of the polymeric prodrug to form stable nanoparticles (NPs). Brush conformation of polyethylene glycol (PEG) side chains endowed the NPs with long-term circulation with a half-life of 16.0 h. The dual-responsive dendritic structure enhanced cellular uptake of NPs and facilitated drug release in response to overexpressed cathepsin B and an acidic pH in the tumor microenvironment, resulting in an enhanced therapeutic effect with a tumor inhibition rate of 72.9% for 4T1 tumor-bearing mice. The NPs were demonstrated to possess great hemocompatibility and biosafety. Therefore, this strategy could provide great insight for the design of poly(oligo-(ethylene glycol) methacrylate)-based copolymers as drug delivery carriers. Statement of significanceWe propose a dual-stimuli-responsive dendronized strategy for improving the cancer therapeutic effect of the poly(oligo-(ethylene glycol) methacrylate) (pOEGMA)-based drug conjugates. The introduction of the functional dendron promotes self-assembly of the polymeric prodrug into nanoparticles, hindering the entanglement of brush oligo-(ethylene glycol) (OEG) chains in the conjugated drugs. The obtained poly OEGMA-GFLG-Dendron-NH-N=DOX nanoparticles maintains long circulation, while addresses the drug release issue due to the presence of high-density PEG. The drug delivery system exhibits a high therapeutic potentcy with negligible side effects.

Antibacterial Cascade Catalytic Glutathione-Depleting MOF Nanoreactors.

Nanozymes with peroxidase-like activity have great application potential in combating pathogenic bacterial infections and are expected to become an alternative to antibiotics. However, the near-neutral pH and high glutathione (GSH) levels in the bacterial infection microenvironment severely limit their applications in antibacterial therapy. In this work, a metal-organic framework (MOF)-based cascade catalytic glutathione-depleting system named MnFe2O4@MIL/Au&GOx (MMAG) was constructed. The MMAG cascade-catalyzed glucose to provide H+ and produces a large amount of toxic reactive oxygen species. In addition, MMAG consumed GSH, which can result in bacterial death more easily. Systematic antibacterial experiments illustrated that MMAG has superior antibacterial effects on both Gram-positive bacteria and Gram-negative bacteria.

Impact of Extracellular pH on Apoptotic and Non-Apoptotic TRAIL-Induced Signaling in Pancreatic Ductal Adenocarcinoma Cells.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is an important mediator of tumor immune surveillance. In addition, its potential to kill cancer cells without harming healthy cells led to the development of TRAIL receptor agonists, which however did not show the desired effects in clinical trials. This is caused mainly by apoptosis resistance mechanisms operating in primary cancer cells. Meanwhile, it has been realized that in addition to cell death, TRAIL also induces non-apoptotic pro-inflammatory pathways that may enhance tumor malignancy. Due to its late detection and resistance to current therapeutic options, pancreatic ductal adenocarcinoma (PDAC) is still one of the deadliest types of cancer worldwide. A dysregulated pH microenvironment contributes to PDAC development, in which the cancer cells become highly dependent on to maintain their metabolism. The impact of extracellular pH (pHe) on TRAIL-induced signaling in PDAC cells is poorly understood so far. To close this gap, we analyzed the effects of acidic and alkaline pHe, both in short-term and long-term settings, on apoptotic and non-apoptotic TRAIL-induced signaling. We found that acidic and alkaline pHe differentially impact TRAIL-induced responses, and in addition, the duration of the pHe exposition also represents an important parameter. Thus, adaptation to acidic pHe increases TRAIL sensitivity in two different PDAC cell lines, Colo357 and Panc1, one already TRAIL-sensitive and the other TRAIL-resistant, respectively. However, the latter became highly TRAIL-sensitive only by concomitant inhibition of Bcl-xL. None of these effects was observed under other pHe conditions studied. Both TRAIL-induced non-apoptotic signaling pathways, as well as constitutively expressed anti-apoptotic proteins, were regulated by acidic pHe. Whereas the non-apoptotic pathways were differently affected in Colo357 than in Panc1 cells, the impact on the anti-apoptotic protein levels was similar in both cell lines. In Panc1 cells, adaptation to either acidic or alkaline pHe blocked the activation of the most of TRAIL-induced non-apoptotic pathways. Interestingly, under these conditions, significant downregulation of the plasma membrane levels of TRAIL-R1 and TRAIL-R2 was observed. Summing up, extracellular pH influences PDAC cells’ response to TRAIL with acidic pHe adaptation, showing the ability to strongly increase TRAIL sensitivity and in addition to inhibit TRAIL-induced pro-inflammatory signaling.

PH and lipase-responsive nanocarrier-mediated dual drug delivery system to treat periodontitis in diabetic rats.

Precise and controlled drug delivery to treat periodontitis in patients with diabetes remains a significant clinical challenge. Nanoparticle-based drug delivery systems offer a potential therapeutic strategy; however, the low loading efficiency, non-responsiveness, and single effect of conventional nanoparticles hinder their clinical application. In this study, we designed a novel self-assembled, dual responsive, and dual drug-loading nanocarrier system, which comprised two parts: the hydrophobic lipid core formed by 1, 2-Distearoyl-sn-glycero-3-phosphoethanolamine-Poly (ethylene glycol) (DSPE-PEG) loaded with alpha-lipoic acid (ALA); and a hydrophilic shell comprising a poly (amidoamine) dendrimer (PAMAM) that electrostatically adsorbed minocycline hydrochloride (Mino). This unique design allows the controlled release of antioxidant/ALA under lipase stimulation from periodontal pathogens and antimicrobial/Mino under the low pH of the inflammatory microenvironment. In vivo and in vitro studies confirmed that this dual nanocarrier could inhibit the formation of subgingival microbial colonies while promoting osteogenic differentiation of cells under diabetic pathological conditions, and ameliorated periodontal bone resorption. This effective and versatile drug-delivery strategy has good potential applications to inhibit diabetes-associated periodontal bone loss.

Real-time monitoring of the pH microenvironment at the interface of multispecies biofilm and dental composites

Bacterial-mediated local pH change plays an important role in altering the integrity of resin dental composite materials in a dynamic environment such as the oral cavity. To address this, we developed a 300-μm-diameter, flexible, solid-state potentiometric pH microsensor capable of detecting and quantifying the local pH microenvironment at the interface of multispecies biofilm and dental resin in real time over 10 days. We used fluorinated poly(3,4-ethylenedioxythiophene) as the back contact in our newly developed pH sensor, along with a PVC-based ion-selective membrane and PTFE-AF coating. The high temporal resolution pH data demonstrated pH changes from 7 to 6 and 7 to 5.8 for the first 2 days and then fluctuated between 6.5 to 6 and 6 to 5.5 for the remaining 8 days with the resin composite or glass slide substrate respectively. We could observe the fluctuations in pH mediated by lactic acid production within the biofilm and the re-establishment of pH back to 7. However, acid production started to overwhelm buffering capacity with the continuous feed of sucrose cycles and reduced the local pH nearer to 5.5. No such changes or fluctuations were observed above the biofilm, as the pH remained at 7.0 ± 0.2 for 10 days. The localized real-time monitoring of the pH within the biofilm showed that the pH shift underneath the biofilm could lead to damage to the underlying material and their interface but cannot be sensed external to the biofilm.

Mitochondrial structural variations in the process of mitophagy

Mitochondrion is one of significant organelles inside cells because it serves as a hub for energy management and intracellular signaling. Internal/external damages on mitochondria would lead to mitochondrial stresses with the malfunctions, accompanying with the changes of morphological structure and abnormal local environments (pH values). Mitophagy is capable of degradation of damaged mitochondrial segments to restore its normal metabolism, dynamics, and biogenesis. The dynamic structural visualization and pH quantification can be helpful for the understanding of mitochondrial functions as well as the diagnosis of disorders linking with this process. In this work, we use confocal laser scanning microscopy, STED super-resolution nanoscopy and fluorescence lifetime imaging microscopy, in conjunction with a mitochondrial probe to image the dynamic changes in the mitochondrial morphology and microenvironmental pH values during mitophagy in live cells, in particular, the structural changes of mitochondrial cristae beyond optical diffraction can be distinguished by STED nanoscopy with/without treatment by CCCP, which will provide a new view for the diagnosis and personalized treatment of mitochondrial dysfunction-related diseases.

Stimuli-responsive nanoplatforms for antibacterial applications.

The continuously increasing bacterial resistance has become a big threat to public health worldwide, which makes it urgent to develop innovative antibacterial strategies. Nanotechnology-based drug delivery systems are considered as promising strategies in combating bacterial infections which are expected to improve the therapeutic efficacy and minimize the side effects. Unfortunately, the conventional nanodrug delivery systems always suffer from practical dilemmas, including incomplete and slow drug release, insufficient accumulation in infected sites, and weak biofilm penetration ability. Stimuli-responsive nanoplatforms are hence developed to overcome the disadvantages of conventional nanoparticles. In this review, we provide an extensive review of the recent progress of endogenous and exogenous stimuli-responsive nanoplatforms in the antibacterial area, including planktonic bacteria, intracellular bacteria, and bacterial biofilms. Taking advantage of the specific infected microenvironment (pH, enzyme, redox, and toxin), the mechanisms and strategies of the design of endogenous stimuli-responsive nanoplatforms are discussed, with an emphasis on how to improve the therapeutic efficacy and minimize side effects. How to realize controlled drug delivery using exogenous stimuli-responsive nanoplatforms especially light-responsive nanoparticles for improved antibacterial effects is another topic of this review. We especially highlight photothermal-triggered drug delivery systems by the combination of photothermal agents and thermo-responsive materials. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies.