A low-barrier proton shared between two aspartates acts as a conformational switch that changes the substrate specificity of the ß-lactamase BlaC.

Serine ß-lactamases inactivate ß-lactam antibiotics in a two-step mechanism comprising acylation and deacylation. For the deacylation step, a water molecule is activated by a conserved glutamate residue to release the adduct from the enzyme. The third-generation cephalosporin ceftazidime is a poor substrate for the class A ß-lactamase BlaC from Mycobacterium tuberculosis but it can be hydrolyzed faster when the active site pocket is enlarged, as was reported for mutant BlaC P167S. The conformational change in the Ω-loop of the P167S mutant displaces the conserved glutamate (Glu166), suggesting it is not required for deacylation of the ceftazidime adduct. Here, we report the characterization of wild type BlaC and BlaC E166A at various pH values. The presence of Glu166 strongly enhances activity against nitrocefin but not ceftazidime, indicating it is indeed not required for deacylation of the adduct of the latter substrate. At high pH wild type BlaC was found to exist in two states, one of which converts ceftazidime much faster, resembling the open state previously reported for the BlaC mutant P167S. The pH-dependent switch between the closed and open states is caused by the loss at high pH of a low-barrier hydrogen bond, a proton shared between Asp172 and Asp179. These results illustrate how readily shifts in substrate specificity can occur as a consequence of subtle changes in protein structure.

Effect of size and pH-sensitivity of liposomes on cellular uptake pathways and pharmacokinetics of encapsulated gemcitabine.

To enhance cytoplasmic delivery efficiency, pH-sensitive liposomes (PSL) have been proposed as a novel strategy. To facilitate clinical translation, this study aims to understand the impact of both size and pH-sensitivity on cellular uptake pathways, intracellular trafficking and pharmacokinetics of liposomes. The large liposomes (130-160 nm) were prepared using thin-film hydration method, while small liposomes (∼60 nm) were fabricated using microfluidics, for both PSL and non-pH-sensitive liposomes (NPSL). Cellular uptake pathways and intracellular trafficking was investigated through confocal imaging with aid of various endocytosis inhibitors. Intracellular gemcitabine delivery by various liposomal formulations was quantified using HPLC, and the cytotoxicity was assessed via cell viability assays. Pharmacokinetics of gemcitabine loaded in various liposomes was evaluated in rats following intravenous administration. Larger liposomes had a higher loading capacity for hydrophilic gemcitabine (7% vs 4%). Small PSL exhibited superior cellular uptake compared to large PSL or NPSLs. Moreover, the alkalization of endosomes significantly attenuated the cellular uptake of PSL. Large liposomes (PSL and NPSL) predominantly entered cells via clathrin-dependent pathway, whereas small liposomes partially utilized caveolae-dependent pathway. However, the long circulation of the liposomes, as measured by the encapsulated gemcitabine, was compromised by both pH-sensitivity and size reduction (9.5 h vs 5.3 h). Despite this drawback, our results indicate that small PSL holds promise as vectors for the next generation of liposomal nanomedicine, owing to their superior cytoplasmic delivery efficiency.

Large liposomes had higher loading capacity for hydrophilic gemcitabine.Reduction of liposome size enhanced drug release from pH-sensitive liposomes.The internalization efficiency of liposomes was enhanced by pH-sensitivity and size reduction.Larger liposomes (>130 nm) enter cells primarily via clathrin-dependent endocytosis, while smaller liposomes (∼60 nm) partially through caveolae-mediated pathway, regardless of the pH-sensitivity.The intracellular payload release from pH-sensitive liposomes was decreased by endosome alkalization using chloroquine.Long circulation of the encapsulated gemcitabine was compromised by the pH-sensitivity and size reduction.

Chirality and pH Influence the Self-Assembly of Antimicrobial Lipopeptides with Diverse Nanostructures.

Chirality plays a crucial role in the self-assembly of biomolecules in nature. Peptides show chirality-dependent conformation and self-assembly. Lipidation of peptides occurs in vivo and has recently been exploited in designed conjugates to drive self-assembly and enhance bioactivity. Here, a library of pH-responsive homochiral and heterochiral lipidated tripeptides has been designed. The designed lipopeptides comprise homochiral C16-YKK or C16-WKK (where all the amino acids are l-isomers), and two heterochiral conjugates C16-Ykk and C16-Wkk (where the two lysines are d-isomers). The self-assembly of all the synthesized lipopeptides in aqueous solution was examined using a combination of spectroscopic methods along with cryogenic-transmission electron microscopy (cryo-TEM) and small-angle X-ray scattering (SAXS). Interestingly, it was observed that at acidic pH all the lipopeptides self-assemble into micelles, whereas at basic pH the homochiral lipopeptides self-assemble into nanofibers, whereas the heterochiral lipopeptides self-assemble into nanotapes and nanotubes. A pH switch was demonstrated using a thioflavin T fluorescence probe of ß-sheet structure present in the extended structures at pH 8. We demonstrate that both chirality and pH in lipopeptides influence the self-assembly behavior of the model tripeptides, which also show promising bioactivity. Good cytocompatibility is observed in hemolytic assays and antimicrobial activity against both Gram-negative and Gram-positive bacteria is shown through the determination of minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC) values and live/dead bacteria staining assay.

Synthesis of a pH/temperature bi-response gallic acid magnetic imprinted polymer for extracting natural product from Galla chinensis.

A pH/temperature bi-responsive gallic acid magnetic imprinted polymer (PTBG-MIP) was synthesized on a Fe3O4@SiO2@KH570 carrier using methacrylic acid (MAA), p-Vinylphenylboronic acid (p-VPBA), and N-isopropyl-acrylamide (NIPAAm) as complex functional monomers. The density functional theory (DFT) was employed to optimize the molar ratio of multi-functional monomers-template complex, which proved to be an effective tool for predicting complex configuration based on electrostatic potential (ESP) analysis and the lowest binding energy. DFT calculation and analysis determined the optimized molar ratio of 2:1:1:1 for GA-MAA-NIPAAm-p-VPBA, which showed good agreement with experimental results. The PTBG-MIP-4 obtained under the optimized conditions exhibited high pH- and temperature- dependence in rebinding the template, displaying a maximum adsorption capacity (Qe) of 62.26 mg g-1 and a highest selection factor (α) of 5.217. Additionally, the PTBG-MIP-4 exhibited exceptional physicochemical properties encompassing magnetization characteristics, morphology, surface sites distribution, and adsorption performance. The application efficiency of this imprinted composite in the extraction and purification of gallic acid from Galla chinensis was remarkably demonstrated.

pH sensitivity of YFPs is reduced upon AlphaRep binding: proof of concept in vitro and in living cells.

Yellow fluorescent proteins (YFPs) are commonly used in biology to track cellular processes, particularly as acceptors in experiments using the Förster Resonant Energy Transfer (FRET) phenomenon. However, their fluorescence intensity is strongly pH-dependent, limiting their utility in acidic environments. Here, we explore the pH sensitivity of YFPs upon binding with an artificial repeat protein (αRep) both in vitro and in living cells. We show that αRep binds to Citrine, with high affinity in the nanomolar range at physiological and acidic pHs, leading to increased thermal stability of the complex. Moreover, αRep binding reduces Citrine's pKa by 0.75 pH units, leading to a decreased sensitivity to pH fluctuations. This effect can be generalized to other YFPs as Venus and EYFP in vitro. An efficient binding of αRep to Citrine has also been observed in living cells both at pH 7.4 and pH 6. This interaction leads to reduced variations of Citrine fluorescence intensity in response to pH variations in cells. Overall, the study highlights the potential of αReps as a tool to modulate the pH sensitivity of YFPs, paving the way for future exploration of biological events in acidic environments by FRET in combination with a pH-insensitive cyan donor.

Carrageenan-based sustainable biomaterials for intelligent food packaging: A review.

This article explores the use of carrageenan-based biomaterials in developing sustainable and efficient intelligent food packaging solutions. The research in this field has seen a notable surge, evident from >1000 entries in databases such as Web of Science, PubMed and Science Direct between 2018 and 2023. Various film preparation techniques are explored, including solvent casting, layer-by-layer (LbL) assembly, and electrospinning. Solvent casting is commonly used to incorporate active compounds, while LbL assembly and electrospinning are favored for enhancing mechanical properties and solubility. Carrageenan's film-forming characteristics enable the production of transparent films, ideal for indicator films that facilitate visual inspection for color changes indicative of pH variations, crucial for detecting food spoilage. Surface properties can be modified using additives like plant extracts to regulate moisture interaction, affecting shelf life and food safety. These materials' antioxidant and antimicrobial attributes are highlighted, demonstrating their efficacy against pathogens such as E. coli.

Bioactive pH-sensitive nanoemulsion in melanoma cell lines.

Melanoma is an aggressive form of skin cancer with elevated propensity to metastasize. One of the major critical issues in the treatment of oncological patients is represented by the development of toxicity and resistance to the available therapies. Great progress has been made in the field of nanotechnologies to limit the unwanted effects of anti-cancer treatments. We explored the potential of creating oil-in-water nanoemulsions composed of oleic acid, as a bioactive carrier for lipophilic drug delivery. This bioactive nanoemulsion was loaded with Curcumin, a natural fluorescent lipophilic compound, used as a model drug to evaluate nanoemulsion capability to: i) encapsulate the lipophilic moiety; ii) interact with the specific cells, and iii) improve the efficacy of the loaded model drug compared to the free one. Therefore, we evaluated the physical-chemical features of Curcumin-loaded nanoemulsions, confirming their pH sensibility and their stability over time. Moreover, the nanoemulsions were able to preserve the loaded Curcumin by degradation/destabilization phenomena. Finally, we verified some of the biological functions of Curcumin delivered by nanoemulsions in the B16F10 melanoma cell line. We obtained evidence of the biological action of Curcumin, suggesting oleic-based nanoemulsions as an efficient nanocarrier for lipophilic drug delivery.

Fine-tuning pH sensor H98 by remote essential residues in the hydrogen-bond network of mTASK-3.

TASK-3 generates a background K+ conductance which when inhibited by acidification depolarizes membrane potential and increases cell excitability. These channels sense pH by protonation of histidine residue H98, but recent evidence revealed that several other amino acid residues also contribute to TASK-3 pH sensitivity, suggesting that the pH sensitivity is determined by an intermolecular network. Here we use electrophysiology and molecular modeling to characterize the nature and requisite role(s) of multiple amino acids in pH sensing by TASK-3. Our results suggest that the pH sensor H98 and consequently pH sensitivity is influenced by remote amino acids that function as a hydrogen-bonding network to modulate ionic conductivity. Among the residues in the network, E30 and K79 are the most important for passing external signals near residue S31 to H98. The hydrogen-bond network plays a key role in selectivity or pH sensing in mTASK-3, and E30 and S31 in the network can modulate the conductive properties (E30) or reverse the pH sensitivity and selectivity of the channel (S31). Molecular dynamics simulations and pK1/2 calculation revealed that double mutants involving H98 + S31 primarily regulate the structure stability of the pore selectivity filter and pore loop regions, further strengthen the stability of the cradle suspension system, and alter the ionization state of E30 and K79, thereby preventing pore conformational change that normally occurs in response to varying extracellular pH. These results demonstrate that crucial residues in the hydrogen-bond network can remotely tune the pH sensing of mTASK-3 and may be a potential allosteric regulatory site for therapeutic molecule development.

A novel acidic pH-dependent metacaspase governs defense-response against pathogens in tomato.

The importance of metacaspases in programmed cell death and tissue differentiation is known, but their significance in disease stress response, particularly in a crop plant, remained enigmatic. We show the tomato metacaspase expression landscape undergoes differential reprogramming during biotrophic and necrotrophic modes of pathogenesis; also, the metacaspase activity dynamics correlate with the disease progression. These stresses have contrasting effects on the expression pattern of SlMC8, a Type II metacaspase, indicating that SlMC8 is crucial for stress response. In accordance, selected biotic stress-related transcription factors repress SlMC8 promoter activity. Interestingly, SlMC8 exhibits maximum proteolysis at an acidic pH range of 5-6. Molecular dynamics simulation identified the low pH-driven protonation event of Glu246 as critical to stabilize the interaction of SlMC8 with its substrate. Mutagenesis of Glu246 to charge-neutral glutamine suppressed SlMC8's proteolytic activity, corroborating the importance of the amino acid in SlMC8 activation. The glutamic acid residue is found in an equivalent position in metacaspases having acidic pH dependence. SlMC8 overexpression leads to heightened ROS levels, cell death, and tolerance to PstDC3000, and SlMC8 repression reversed the phenomena. However, the overexpression of SlMC8 increases tomato susceptibility to necrotrophic Alternaria solani. We propose that SlMC8 activation due to concurrent changes in cellular pH during infection contributes to the basal resistance of the plant by promoting cell death at the site of infection, and the low pH dependence acts as a guard against unwarranted cell death. Our study confirms the essentiality of a low pH-driven Type II metacaspase in tomato biotic stress-response regulation.

Plant betalains-mixed active/intelligent films for meat freshness monitoring: A review of the fabrication parameters.

The plant pigments called betalains are nutritionally safe polar compounds. They are subdivided into betaxanthins (having orange to yellow hues) and betacyanins (purple to red violet hues). Betacyanins change color with a change in pH, particularly in the range 6-8 and 9-11. Perishable foods like fish, chicken, beef, pork, and others tend to release total volatile base-nitrogen (TVB-N) during storage or deterioration, which leads to a change in the pH of pH-sensitive materials in the vicinity. pH-sensitive pigment-incorporated polymeric films with inherent active properties (or active/intelligent films) are increasingly being studied as an alternative to synthetic pH indicators to detect the accumulation of TVB-N by changing its color to indicate the stage of perishable food spoilage. There are many methods of developing such films under different conditions using different bio-based biodegradable polymer(s) and biocompatible plasticizer combinations. Among the reported methods, solution casting method has been the preferred one in most studies covered in this review. This method can be carried out under mild conditions. As such, betacyanins-incorporated polymeric films essentially require mild processing conditions because of their heat sensitivity, which will invariably affect the performance in food freshness monitoring. In this review, film fabrication parameters like temperature and duration of dissolution of polymers, plasticizer concentration, pH of the film-forming solution, film drying, and conditioning/aging, have been critically appraised based on the available literature. The lack of studies on the safety of active/intelligent films has been systematically highlighted in this review to focus future studies on this area.

Antiepileptic drug-loaded and multifunctional iron oxide@silica@gelatin nanoparticles for acid-triggered drug delivery.

The current study developed an innovative design for the production of smart multifunctional core-double shell superparamagnetic nanoparticles (NPs) with a focus on the development of a pH-responsive drug delivery system tailored for the controlled release of Phenytoin, accompanied by real-time monitoring capabilities. In this regard, the ultra-small superparamagnetic iron oxide@silica NPs (IO@Si MNPs) were synthesized and then coated with a layer of gelatin containing Phenytoin as an antiepileptic drug. The precise saturation magnetization value for the resultant NPs was established at 26 emu g-1. The polymeric shell showed a pH-sensitive behavior with the capacity to regulate the release of encapsulated drug under neutral pH conditions, simultaneously, releasing more amount of the drug in a simulated tumorous-epileptic acidic condition. The NPs showed an average size of 41.04 nm, which is in the desired size range facilitating entry through the blood-brain barrier. The values of drug loading and encapsulation efficiency were determined to be 2.01 and 10.05%, respectively. Moreover, kinetic studies revealed a Fickian diffusion process of Phenytoin release, and diffusional exponent values based on the Korsmeyer-Peppas equation were achieved at pH 7.4 and pH 6.3. The synthesized NPs did not show any cytotoxicity. Consequently, this new design offers a faster release of PHT at the site of a tumor in response to a change in pH, which is essential to prevent epileptic attacks.

Role of Histidine 310 in Amydetes vivianii firefly luciferase pH and metal sensitivities and improvement of its color tuning properties.

Firefly luciferases emit yellow-green light and are pH-sensitive, changing the bioluminescence color to red in the presence of heavy metals, acidic pH and high temperatures. These pH and metal-sensitivities have been recently harnessed for intracellular pH indication and toxic metal biosensing. However, whereas the structure of the pH sensor and the metal binding site, which consists mainly of two salt bridges that close the active site (E311/R337 and H310/E354), has been identified, the specific role of residue H310 in pH and metal sensing is still under debate. The Amydetes vivianii firefly luciferase has one of the lowest pH sensitivities among the group of pH-sensitive firefly luciferases, displaying high bioluminescent activity and special spectral selectivity for cadmium and mercury, which makes it a promising analytical reagent. Using site-directed mutagenesis, we have investigated in detail the role of residue H310 on pH and metal sensitivity in this luciferase. Negatively charged residues at position 310 increase the pH sensitivity and metal sensitivity; H310G considerably increases the size of the cavity, severely impacting the activity, H310R closes the cavity, and H310F considerably decreases both pH and metal sensitivities. However, no substitution completely abolished pH and metal sensitivities. The results indicate that the presence of negatively charged and basic side chains at position 310 is important for pH sensitivity and metals coordination, but not essential, indicating that the remaining side chains of E311 and E354 may still coordinate some metals in this site. Furthermore, a metal binding site search predicted that H310 mutations decrease the affinity mainly for Zn, Ni and Hg but less for Cd, and revealed the possible existence of additional binding sites for Zn, Ni and Hg.

Preparation of pH-sensitive carboxymethyl chitosan nanoparticles loaded with ginsenoside Rb1 and evaluation of drug release in vitro.

Oral absorption of ginsenoside Rb1 (Rb1) is often hindered by the gastrointestinal tract. Carboxymethyl chitosan deoxycholic acid loaded with ginsenoside Rb1 nanoparticles (CMDA@Rb1-NPs), were prepared as a delivery system using a self-assembly technique with amphipathic deoxycholic acid grafted carboxymethyl chitosan as the carrier, which improved the stability and embedding rate of Rb1. In addition, the CMDA@Rb1-NPs was encapsulated with sodium alginate by ion crosslinking method with additional layer (CMDAlg@Rb1-NPs). Scanning electron microscopy showed that the nanoparticles were spherical, evenly distributed, smooth and without obvious adhesion. By evaluating drug loading, entrapment efficiency, the encapsulation efficiency of Rb1 increased from 60.07 % to 72.14 % after grafting deoxycholic acid improvement and optimization. In vitro release results showed that the cumulative release of Rb1 by CMDAlg-NPs showed a pH dependent effect, which was <10 % in simulated gastric juice with pH 1.2, completely released with pH 7.4 for about 48 h. In addition, Rb1 and CMDAlg@Rb1-NPs had inhibitory effects on A549 cells, and the inhibitory effect of CMDAlg@Rb1-NPs was better. Therefore, all results indicated that CMDA/Alg@Rb1 nanoparticles might be a novel drug delivery system to improve the stability and embedding rate of Rb1, and has the potential to be applied in oral pharmaceutical preparations.

Poly-ß-thioester-Based Cross-Linked Nanocarrier for Cancer Cell Selectivity over Normal Cells and Cellular Apoptosis by Triggered Release of Parthenolide, an Anticancer Drug.

Breast cancer is the most prevalent and aggressive type of cancer, causing high mortality rates in women globally. Many drawbacks and side effects of the current chemotherapy force us to develop a robust chemotherapeutic system that can deal with off-target hazards and selectively combat cancer growth, invasiveness, and cancer-initiating cells. Here, a pH-responsive cross-linked nanocarrier (140-160 nm) endowed with poly-ß-thioester functionality (CBAPTL) has been sketched and fabricated for noncovalent firm encapsulation of anticancer drug, parthenolide (PTL) at physiological pH (7.4), which enables sustain release of PTL at relevant endosomal pH (∼5.0-5.3). For this, a bolaamphiphilic molecule integrated with ß-thioester and acrylate functionality was synthesized to fabricate the pH-responsive poly-ß-thioester-based cross-linked nanocarrier via Michael addition click reactions in water. The poly-ß-thioester functionality of CBAPTL hydrolyzes at endosomal acidic conditions, thus leading to the selective release of PTL inside the cancer cell. Cross-linked nanocarriers exhibit high serum stability, dilution insensitivity, and targeted cellular uptake at tumor microenvironment (TME), contrasting normal cells. In vitro study using human MCF-7 breast cancer cells demonstrated that CBAPTL exhibited selective cytotoxicity, reduced clonogenic potential, increased reactive oxygen species (ROS) generation, and arrested the progression of the cell cycle at the G0/G1 phase efficiently. CBAPTL induced apoptosis via downregulating pro-proliferative protein Bcl-2 and upregulating proapoptotic proteins p53, BAD, p21, and cleaved PARP-1. CBAPTL inhibited proliferating signaling by suppressing AKT phosphorylation and p38 expression. CBAPTL also blocked the invasion and migration of MCF-7 cells. CBAPTL effectively inhibits primary and secondary mammosphere formation, thereby preventing cancer-initiating cells' growth. Conversely, CBAPTL has negligible effect on human red blood cells (RBCs) and peripheral blood mononuclear cells (PBMCs). These findings highlight the superior efficacy of CBAPTL compared to PTL alone in suppressing cancer cell growth, inducing apoptosis, and preventing invasiveness of MCF-7 cells. Thus, CBAPTL could be considered a possible selective chemotherapeutic cargo against breast cancer without affecting normal cells.

Synthesis and Photophysical Characterization of a pH-Sensitive Quadracyclic Uridine (qU) Analogue.

Fluorescent base analogues (FBAs) have become useful tools for applications in biophysical chemistry, chemical biology, live-cell imaging, and RNA therapeutics. Herein, two synthetic routes towards a novel FBA of uracil named qU (quadracyclic uracil/uridine) are described. The qU nucleobase bears a tetracyclic fused ring system and is designed to allow for specific Watson-Crick base pairing with adenine. We find that qU absorbs light in the visible region of the spectrum and emits brightly with a quantum yield of 27 % and a dual-band character in a wide pH range. With evidence, among other things, from fluorescence lifetime measurements we suggest that this dual emission feature results from an excited-state proton transfer (ESPT) process. Furthermore, we find that both absorption and emission of qU are highly sensitive to pH. The high brightness in combination with excitation in the visible and pH responsiveness makes qU an interesting native-like nucleic acid label in spectroscopy and microscopy applications in, for example, the field of mRNA and antisense oligonucleotide (ASO) therapeutics.

Synthesis of an aggregation-induced emission (AIE) dye with pH-sensitivity based on tetraphenylethylene-pyridine for fluorescent nanoparticles and its applications in bioimaging and in vitro anti-tumor effect.

In this contribution, a novel AIE monomers 2-(4-styrylphenyl)- 1,2-diphenylvinyl)styryl)pyridine (SDVPY) with smart fluorescent pH-sensitivity basing on tetraphenylethylene-pyridine were successfully synthesized for the first time, subsequently, a series of amphiphilic copolymers PEG-PY were achieved by reversible addition-fragmentation chain transfer (RAFT) polymerization of SDVPY and poly(ethylene glycol) methacrylate (PEGMA), which would self-assemble in water solution to form core-shell nanoparticles (PEG-PY FONs) with about 150 nm diameter. The PEG-PY FONs showed obvious fluorescence response to Fe3+, HCO3- and CO32- ions in aqueous solution owing to their smart pH-sensitivity and AIE characteristics, and their maximum emission wavelength could reversibly change from 525 nm to 624 nm. The as-prepared PEG-PY FONs showed also prospective application in cells imaging with the variable fluorescence for different pH cells micro-environment. When PEG-PY copolymers self-assembled with the anti-tumor drug paclitaxel (PTX), the obtained PY-PTX FONs could effectively deliver and release PTX with pH-sensitivity, and could be easily internalized by A549 cells and located at the cytoplasm with high cytotoxicity, which was further confirmed by the Calcein-AM/PI staining of dead and alive A549 cells. Moreover, the flow cytometry results indicated that the PY-PTX FONs could obviously induce the apoptosis of A549 cells, which further showed the great potential of PY-PTX FONs in the application of tumors therapy.

Chlorophyllin-Containing Copolymers and Their Responsive Properties.

Copper-chlorophyllin is a water-soluble derivative of chlorophylls and shows low cytotoxicity and antimutagenic properties in cultured cells. It has multiple applications, including its use as a photosensitizer in photothermal therapy because of its green light-activated photothermal performance. In this work, it was copolymerized with a poly(ethylene glycol) methacrylic monomer to yield random copolymers by free radical polymerization, which showed dual temperature- and pH-dependent phase transitions in aqueous solutions. The cloud points of the copolymer solutions were raised by lowering the pH of the aqueous solutions due to the protonation of the carboxylic groups on the chlorophyllin moieties, which decreased the overall hydrophilicity of the polymers. At low pH values, complete protonation of the carboxylic acid groups of the chlorophyllin moieties led to an irreversible aggregation of the copolymers in water. The incorporation of chlorophyllin in the copolymer improved its stability over its single molecular form.

Using Mesoporous Silica-Based Dual Biomimetic Nano-Erythrocytes for an Improved Antitumor Effect.

The nano-delivery system with a dual biomimetic effect can penetrate deeper in tumor microenvironments (TMEs) and release sufficient antitumor drugs, which has attracted much attention. In this study, we synthesized erythrocyte-like mesoporous silica nanoparticles (EMSNs) as the core loaded with doxorubicin (DOX) and coated them with calcium phosphate (CaP) and erythrocyte membrane (EM) to obtain DOX/EsPMs. The transmission electron microscopy (TEM), fluorescent co-localization and protein bands of SDS-PAGE were used to confirm the complete fabrication of EsPMs. The EsPMs with erythrocyte-like shape exhibited superior penetration ability in in vitro diffusion and tumor-sphere penetration experiments. Intracellular Ca2+ and ROS detection experiments showed that the CaP membranes of EsPMs with pH-sensitivity could provide Ca2+ continuously to induce reactive oxide species' (ROS) generation in the TME. The EM as a perfect "camouflaged clothing" which could confuse macrophagocytes into prolonging blood circulation. Hemolysis and non-specific protein adsorption tests proved the desirable biocompatibility of EsPMs. An in vivo pharmacodynamics evaluation showed that the DOX/EsPMs group had a satisfactory tumor-inhibition effect. These advantages of the nano-erythrocytes suggest that by modifying the existing materials to construct a nano-delivery system, nanoparticles will achieve a biomimetic effect from both their structure and function with a facilitated and sufficient drug release profile, which is of great significance for antitumor therapy.