pH-responsive biocompatible fluorescent polymer nanoparticles based on phenylboronic acid for intracellular imaging and drug delivery

Stimuli-responsive biomaterials: smart avenue toward 4D bioprinting

3D bioprinting is an advanced technology combining cells and bioactive molecules within a single bioscaffold; however, this scaffold cannot change, modify or grow in response to a dynamic implemented environment. Lately, a new era of smart polymers and hydrogels has emerged, which can add another dimension, e.g., time to 3D bioprinting, to address some of the current approaches' limitations. This concept is indicated as 4D bioprinting. This approach may assist in fabricating tissue-like structures with a configuration and function that mimic the natural tissue. These scaffolds can change and reform as the tissue are transformed with the potential of specific drug or biomolecules released for various biomedical applications, such as biosensing, wound healing, soft robotics, drug delivery, and tissue engineering, though 4D bioprinting is still in its early stages and more works are required to advance it. In this review article, the critical challenge in the field of 4D bioprinting and transformations from 3D bioprinting to 4D phases is reviewed. Also, the mechanistic aspects from the chemistry and material science point of view are discussed too.

Targeted pH-responsive delivery of rosmarinic acid via phenylboronic acid functionalized mesoporous silica nanoparticles for liver and lung cancer therapy

Currently, chemotherapy is one of the most practiced approaches for the treatment of cancers. However, existing chemotherapeutic drugs have poor aqueous solubility, poor selectivity, higher systematic toxicity, and poor target accumulation. In this study, we designed and synthesized a boronic acid/ester-based pH-responsive nano-valve that specifically targets the microenvironment in cancer cells. The nano-valve comprises phenylboronic acid-coated mesoporous silica nanoparticles (B-MSN) loaded with polyphenolic compound Rosmarinic acid (ROS-B-MSN). The nano-valve was further coated with lignin (LIG) to achieve our desired LIG-ROS-BMSN nano-valve for targeted chemotherapy against Hep-G2 and NCI-H460 cell lines. The structure and properties of NPs were characterized by Fourier-transformed infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) in combination with EDX, and Dynamic light scattering (DLS). The outcomes revealed that the designed LIG-ROS-BMSN were in the nanorange (144.1 ± 0.70 nm), had negative Zeta potential (-15.7 ± 0.46 mV) and had a nearly spherical morphology. In vitro, drug release investigations showed a controlled pH-dependent release profile under mild acidic conditions that could enhance the targeted chemotherapeutic response against cancer in mild acidic environments. The obtained LIG-ROS-BMSN nano valve achieved significantly lower IC50 values of (1.70 ± 0.01 μg/mL and 3.25 ± 0.14 μg/mL) against Hep-G2 and NCI-H460 cell lines as compared to ROS alone, which was (14.0 ± 0.7 μg/mL and 29.10 ± 0.25 μg/mL), respectively. The cellular morphology before and after treatment was further confirmed via inverted microscopy. The outcomes of the current study imply that our designed LIG-ROS-BMSN nanovalve is a potential carrier for cancer chemotherapeutics.

A current era in pulsatile drug delivery system: Drug journey based on chronobiology

Almost all biological processes in the human body are regulated by circadian rhythm, which results in drastically different biochemical and physiological conditions throughout a 24 h period. Hence, suitable drug delivery systems should be efficiently monitored to attain the required therapeutic plasma concentration and therapeutic drug responses when needed as per chrono pharmacological concepts. "Chronotherapy" is the fast and transient release of a particular quantity of drug substance post a predetermined off-release period, termed as 'lag time'. Due to rhythmic variations, it is typically unnecessary to administer a medicine drug in an unhealthy condition constantly. Pulsatile drug delivery systems have received a lot of attention in pharmaceutical development because they give a quick or rate-controlled drug release after administration, followed by an anticipated lag period. Patients with various illnesses, such as asthma, hypertension, joint inflammation, and ulcers, can benefit from a pulsatile drug delivery system. Thus, a pulsatile drug delivery system may be a potential system for managing different diseases. This review mainly focuses on pulsatile drug delivery systems. It reviews and discusses the rationale, drug release mechanism, need, and system classification. In addition, it covers mainly externally regulated pulsatile drug delivery systems and recent advances in pulsatile systems like artificial intelligence and 3D printing. It also covers the ethical issues associated with pulsatile drug delivery systems.

The interaction between phenylboronic acid derivatives and active ingredients with diphenol structure of traditional Chinese medicine

Many active ingredients of traditional Chinese medicine with important pharmacological effects always have glycol or diphenol structure, which lays a foundation for the combination with phenylboronic acid (PBA) derivatives to form cyclic boronic esters compounds. Herein, four important pharmacological active ingredients, namely baicalein, baicalin, gallic acid and protocatechuic acid, were chosen to study the interaction with PBA derivatives. Five PBA derivatives of 3-aminophenylboronic acid monohydrate (APBA), 3-acrylaminophenylboronic acid (AAPBA), poly(3-acrylaminophenylboronic acid) (PAAPBA), poly([poly(ethylene glycol) methacrylate-block-3-acrylaminophenylboronic acid]) (PEbPB), and poly[poly(ethylene glycol) methacrylate-random-3-acrylaminophenylboronic acid] (PErPB) were used. The interactions between five PBA derivatives and four active ingredients were explored by fluorescent spectrophotometer using the alizarin red (ARS) method. The fluorescent intensity of PBA derivative-ARS-active ingredient mixture was decreasing with the increasing concentrations of active ingredients. In comparison, the fluorescent intensity of PAAPBA, PEbPB, and PErPB showed an obviously decrease after active ingredients were added, while the fluorescent intensity of APBA and AAPBA showed a gradually decrease after active ingredients were added. These results indicated a stronger interaction between PBA polymers and active ingredients than that of APBA and AAPBA. Simultaneously, PEbPB and PErPB could enhance cellular uptake of baicalin in A549 cells. This research provided new strategies for improving the bioavailability and water solubility, extending the circulation time, and wider application of the active ingredients of traditional Chinese medicine in the prevention and therapy of diseases.

An Integrated Tumor Microenvironment Responsive Polymeric Micelle for Smart Drug Delivery and Effective Drug Release

Tumor microenvironment (TME) responsive polymeric micelles are promising carriers for drug delivery. In order to meet the needs of various applications, multifarious TME-responsive switches are used to construct smart polymeric micelles, which causes the complexity and corpulence of the polymeric micelle system and increases the difficulty of preparation. In this study, we designed and synthesized an ingenious TME-responsive switch through grafting disulfide bond-modified piperidinepropionic acid (CPA) on copolymer poly(ethylene glycol)-b-poly(aspartate)(PEG-b-PAsp) and built a novel pH/reduction-responsive PEG-b-PAsp-g-CPA polymeric micelle delivery system. The CPA-pendants can reverse the surface charge of the polymeric micelle from negative to positive at pH 6.5 because of the protonation of piperidine groups, thereby enhancing the internalization of cell. Subsequently, more piperidine groups are protonated at pH 5.0 which will increase the hydrophilicity of polymeric micelles and cause the hydrophobic core to swell, thus making the disulfide bonds packed in the core to be more easily broken by GSH. With the synergistic effect of the pH-triggered protonation of piperidine groups and reduction triggered break of disulfide bonds, the polymeric micelles will disintegrate and achieve efficient intracellular drug release. The TME-responsive polymeric micelles exhibited good biological safety, enhanced internalization, and rapid intracellular doxorubicin (DOX) release in vitro. Moreover, the PEG-b-PAsp-g-CPA/DOX polymeric micelles showed excellent antitumor efficacy and low systemic toxicity in lung tumor-bearing BALB/C mice. These results indicated that the novel integrated TME-responsive switch CPA helps the PEG-b-PAsp-g-CPA polymeric micelles to obtain excellent TME-responsiveness and antitumor drug delivery capabilities, while it also makes the preparation of TME-responsive polymeric micelles simpler and more convenient. This work provides a new idea for the architecture of TME-responsive polymeric micelles.

Self-assembled fluorescent hybrid nanoparticles-mediated collaborative lncRNA CCAT1 silencing and curcumin delivery for synchronous colorectal cancer theranostics

Background

Cancer synergistic therapy strategy in combination with therapeutic gene and small molecule drug offers the possibility to amplify anticancer efficiency. Colon cancer-associated transcript-1 (CCAT1) is a well identified oncogenic long noncoding RNA (lncRNA) exerting tumorigenic effects in a variety of cancers including colorectal cancer (CRC).

Results

In the present work, curcumin (Cur) and small interfering RNA targeting lncRNA CCAT1(siCCAT1) were co-incorporated into polymeric hybrid nanoparticles (CSNP), which was constructed by self-assembling method with two amphiphilic copolymers, polyethyleneimine-poly (d, l-lactide) (PEI-PDLLA) and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy (polyethylene glycol) (DSPE-mPEG). Owing to the multicolor fluorescence characteristics of PEI-PDLLA, the constructed CSNP could be served as a theranostic nanomedicine for synchronous therapy and imaging both in vitro and in vivo. Resultantly, proliferation and migration of HT-29 cells were efficiently inhibited, and the highest apoptosis ratio was induced by CSNP with coordination patterns. Effective knockdown of lncRNA CCAT1 and concurrent regulation of relevant downstream genes could be observed. Furthermore, CSNP triggered conspicuous anti-tumor efficacy in the HT-29 subcutaneous xenografts model with good biosafety and biocompatibility during the treatment.

Conclusion

On the whole, our studies demonstrated that the collaborative lncRNA CCAT1 silencing and Cur delivery based on CSNP might emerge as a preferable and promising strategy for synergetic anti-CRC therapy.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-00981-7.

Combinatorial miRNA-34a replenishment and irinotecan delivery via auto-fluorescent polymeric hybrid micelles for synchronous colorectal cancer theranostics

The synergistic combination of microRNA (miRNA) modulation and chemotherapy has emerged as an effective strategy to combat cancer. Irinotecan (IRI) is a potent antitumor chemotherapeutic in clinical practice and has been used for treating various malignant tumors, including colorectal cancer (CRC). However, IRI is not effective for advanced CRC or metastatic behavior. Herein, novel polymeric hybrid micelles were engineered based on two different amphiphilic copolymers, polyethyleneimine-poly(d,l-lactide) (PEI-PLA) and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy (polyethyleneglycol) (DSPE-PEG), in which IRI and a tumor suppressive microRNA-34a (miR-34a) gene were efficiently co-loaded (MINPs) to achieve a chemo-miRNA combination therapy against CRC. MINPs were successfully constructed by two-step film dispersion and electrostatic interaction methods. IRI and miR-34a could be efficaciously encapsulated as MINPs and transferred to CRC cells. After encapsulation, MINPs would then upregulate miR-34a expression and regulate miR-34a-related downstream genes, which in turn led to enhanced cell cytotoxicity and apoptosis ratios. MINPs presented an excitation-dependent multi-wavelength emission feature due to the intrinstic fluorescence properties of PEI-PLA and could be utilized for in vitro/vivo imaging. According to the in vivo experimental results, MINPs possess the great characteristic of accumulating in situ in a tumor site and lightening it after intravenous administration. Furthermore, MINPs presented extraordinary antitumor efficacy owing to the combined therapy effects of IRI and miR-34a with good biocompability. Overall, our findings validated MINPs-mediated miR-34a replenishment and IRI co-delivery to serve as an effective theranostic platform and provided an innovative horizon for combining chemo-gene therapy against CRC.

Stimuli-Responsive Multifunctional Phenylboronic Acid Polymers Via Multicomponent Reactions: From Synthesis to Application

Stimuli-responsive polymers undergo changes under different environmental conditions. Among them, phenylboronic acid (PBA) containing polymers (PBA-polymers) are unique, because they can selectively react with diols to generate borates that are sensitive to pH, sugars, and H₂ O₂ , and can be effectively used to synthesize smart drug carriers and self-healing hydrogels. Recently, multifunctional PBA-polymers (MF-PBA-polymers) have been developed using multicomponent reactions (MCRs) to introduce PBA groups into polymer structures. These MF-PBA-polymers have features similar to those of traditional PBA-polymers; moreover, they exhibit additional properties, such as fluorescence, antimicrobial activity, and antioxidant capability, when different MCRs are used. In this mini review, the preparation of these MF-PBA-polymers are summarized and the new properties/functions that have been introduced into these polymers using different MCRs are discussed. The uses of these MF-PBA-polymers as fluorescent cell anticoagulants, drug carriers, and gelators of functional self-healing hydrogels have been discussed. Additionally, the challenges encountered during their preparation are discussed and also the future developments in this field are touched upon.

ROS-Responsive and active targeted drug delivery based on conjugated polymer nanoparticles for synergistic chemo-/photodynamic therapy

Stimuli-responsive and active targeted drug release is highly significant and challenging for precise and effective cancer therapy. Herein, a reactive oxygen species (ROS)-responsive drug delivery system iRGD-BDOX@CPNs with active targeting for chemo-/photodynamic (PDT) synergistic therapy has been reported. This nanocarrier iRGD-BDOX@CPNs is constructed by the self-assembly of conjugated polymer poly(fluorene-co-vinylene) (PFV), prodrug BDOX (doxorubicin modified with a phenylboronic acid ester group) and an amphiphilic polymer (DSPE-PEG) modified with internalized RGD (DSPE-PEG-iRGD). The hydrophobic inner cores formed by PFV main chains tightly enclose BDOX. Due to PFV generating many ROS by light triggering, the BDOX prodrug can be in situ activated, resulting in the highly efficient drug release. In addition, the remarkable fluorescence recovery could be used for real-time monitoring of drug delivery and guiding antitumor therapy. Contributing to the specific recognition between iRGD and integrin αvβ3 receptors over-expressed on the surface of tumor cells, the active targeting and uptake of iRGD-BDOX@CPNs in tumor cells are greatly enhanced. The prominent anti-cancer effect of iRGD-BDOX@CPNs is realized by targeted drug delivery and synergistic therapeutic effects of PDT/chemotherapy. This study illustrates that the development of ROS-responsive and targeted drug delivery nanocarriers iRGD-BDOX@CPNs provides a new insight for controllable drug release and tumor precision therapy.

Non-isotope enriched phenylboronic acid-decorated dual-functional nano-assembles for an actively targeting BNCT drug

The feasibility of boron neutron capture therapy (BNCT) greatly depends on the selective accumulation of ¹⁰B in tumors. The p-boronophenylalanine-fructose (BPA-f) complex has been established as a conventional BNCT agent due to its preferential uptake into tumors, which is driven by amino acid transporters. However, the retention of BPA-f in tumors is highly limited because of an antiport mechanism, which is regulated by a gradient of amino acid concentration across the cancer cell membrane. Thus, to preserve a high ¹⁰B concentration in tumors, patients are inevitably subjected to a constant intravenous infusion. To this end, we employed a phenylboronic acid (PBA)-decorated polymeric nanoparticle (Nano^PBA) as a sialic acid-targeting BNCT agent. In this manner, the PBA can exhibit dual functionalities, i.e., exhibiting a neutron capture capacity and hypersialyated cancer cell targeting effect. Our developed Nano^PBA possesses a supramolecular structure composed of a core and shell comprised of poly(lactic acid) (PLA) and poly(ethylene glycol) (PEG) segments, respectively. The PBA moiety is installed at the PEG end, providing an unusually strong targeting effect, supposedly via multivalent binding onto the cancer cell membrane. As in BNCT, we verified the feasibility of Nano^PBA against a B16 melanoma-bearing mouse model. By virtue of efficient tumor targeting, even at a 100-fold lower dose than BPA-f, the Nano^PBA achieved a potent antitumor effect.

Graphene oxide and its derivatives as promising In-vitro bio-imaging platforms

Intrinsic fluorescence and versatile optical properties of Graphene Oxide (GO) in visible and near-infrared range introduce this nanomaterial as a promising candidate for numerous clinical applications for early-diagnose of diseases. Despite recent progresses in the impact of major features of GO on the photoluminescence properties of GO, their modifications have not yet systematically understood. Here, to study the modification effects on the fluorescence behavior, poly ethylene glycol (PEG) polymer, metal nanoparticles (Au and Fe3O4) and folic acid (FA) molecules were used to functionalize the GO surface. The fluorescence performances in different environments (water, DMEM cell media and phosphate buffer with two different pH values) were assessed through fluorescence spectroscopy and fluorescent microscopy, while Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) and Scanning electron microscopy (SEM) were utilized to evaluate the modifications of chemical structures. The modification of GO with desired molecules improved the photoluminescence property. The synthesized platforms of GO-PEG, GO-PEG-Au, GO-PEG-Fe3O4 and GO-PEG-FA illustrated emissions in three main fluorescence regions (blue, green and red), suitable for tracing and bio-imaging purposes. Considering MTT results, these platforms potentially positioned themselves as non-invasive optical sensors for the diagnosis alternatives of traditional imaging agents.

Acid-Responsive and Biologically Degradable Polyphosphazene Nanodrugs for Efficient Drug Delivery

To enhance the therapeutic effects and reduce the damage to normal tissues in cancer chemotherapy, it is indispensable to develop drug delivery carriers with controllable release and good biocompatibility. In this work, acid-responsive and degradable polyphosphazene (PPZ) nanoparticles were synthesized by the reaction of hexachlorotripolyphosphonitrile (HCCP) with 4-hydroxy-benzoic acid (4-hydroxy-benzylidene)-hydrazide (HBHBH) and anticancer drug doxorubicin (DOX). The controlled release of DOX could be realized based on the acid responsiveness of acylhydrazone in HBHBH. Experimental results showed that polyphosphazene nanoparticles remained stable in the body's normal fluids (pH ∼ 7.4), while they were degraded and controllable release of DOX in an acidic environment such as tumors (pH ∼ 6.8) and lysosome and endosome (∼5.0) in cancer cells In particular, the doxorubicin (DOX)-loading ratio was fair high and could be tuned from 10.6 to 52.6% by changing the dosing ratio of DOX to HBHBH. Meanwhile, the polyphosphazene nanodrugs showed excellent toxicity to tumor cells and reduced the side effect to normal cells both in vitro and in vivo due to their enhanced permeability and retention (EPR) effect and pH-sensitive degradation properties. Therefore, the constructed pH-sensitive drug delivery system has great potential for cancer chemotherapy.

Recent advances in theranostic polymeric nanoparticles for cancer treatment: A review

Nanotheranostics is fast-growing pharmaceutical technology for simultaneously monitoring drug release and its distribution, and to evaluate the real time therapeutic efficacy through a single nanoscale for treatment and diagnosis of deadly disease such as cancers. In recent two decades, biodegradable polymers have been discovered as important carriers to accommodate therapeutic and medical imaging agents to facilitate construction of multi-modal formulations. In this review, we summarize various multifunctional polymeric nano-sized formulations such as polymer-based super paramagnetic nanoparticles, ultrasound-triggered polymeric nanoparticles, polymeric nanoparticles bearing radionuclides, and fluorescent polymeric nano-sized formulations for purpose of theranostics. The use of such multi-modal nano-sized formulations for near future clinical trials can assist clinicians to predict therapeutic properties (for instance, depending upon the quantity of drug accumulated at the cancerous site) and observed the progress of tumor growth in patients, thus improving tailored medicines.

Phenylboronic Acid-polymers for Biomedical Applications

Background:

Phenylboronic acid-polymers (PBA-polymers) have attracted tremendous attention as potential stimuli-responsive materials with applications in drug-delivery depots, scaffolds for tissue engineering, HIV barriers, and biomolecule-detecting/sensing platforms. The unique aspect of PBA-polymers is their interactions with diols, which result in reversible, covalent bond formation. This very nature of reversible bonding between boronic acids and diols has been fundamental to their applications in the biomedical area.

Methods:

We have searched peer-reviewed articles including reviews from Scopus, PubMed, and Google Scholar with a focus on the 1) chemistry of PBA, 2) synthesis of PBA-polymers, and 3) their biomedical applications.

Results:

We have summarized approximately 179 papers in this review. Most of the applications described in this review are focused on the unique ability of PBA molecules to interact with diol molecules and the dynamic nature of the resulting boronate esters. The strong sensitivity of boronate ester groups towards the surrounding pH also makes these molecules stimuli-responsive. In addition, we also discuss how the re-arrangement of the dynamic boronate ester bonds renders PBA-based materials with other unique features such as self-healing and shear thinning.

Conclusion:

The presence of PBA in the polymer chain can render it with diverse functions/ relativities without changing their intrinsic properties. In this review, we discuss the development of PBA polymers with diverse functions and their biomedical applications with a specific focus on the dynamic nature of boronate ester groups.

Reduction-Triggered Paclitaxel Release Nano-Hybrid System Based on Core-Crosslinked Polymer Dots with a pH-Responsive Shell-Cleavable Colorimetric Biosensor

Herein, we describe the fabrication and characterization of carbonized disulfide core-crosslinked polymer dots with pH-cleavable colorimetric nanosensors, based on diol dye-conjugated fluorescent polymer dots (L-PD), for reduction-triggered paclitaxel (PTX) release during fluorescence imaging-guided chemotherapy of tumors. L-PD were loaded with PTX (PTX loaded L-PD), via π-π stackings or hydrophobic interactions, for selective theragnosis by enhanced release of PTX after the cleavage of disulfide bonds by high concentration of glutathione (GSH) in a tumor. The nano-hybrid system showed fluorescence quenching behavior with less than 2% of PTX released under physiological conditions. However, in a tumor microenvironment, the fluorescence recovered at an acidic-pH, and PTX (approximately 100% of the drug release) was released efficiently out of the matrix by reduction caused by the GSH level in the tumor cells, which improved the effectiveness of the cancer treatment. Therefore, the colorimetric nanosensor showed promising potential in distinguishing between normal and cancerous tissues depending on the surrounding pH and GSH concentrations so that PTX can be selectively delivered into cancer cells for improved cancer diagnosis and chemotherapy.

Stimuli-Responsive Drug Release from Smart Polymers

Over the past 10 years, stimuli-responsive polymeric biomaterials have emerged as effective systems for the delivery of therapeutics. Persistent with ongoing efforts to minimize adverse effects, stimuli-responsive biomaterials are designed to release in response to either chemical, physical, or biological triggers. The stimuli-responsiveness of smart biomaterials may improve spatiotemporal specificity of release. The material design may be used to tailor smart polymers to release a drug when particular stimuli are present. Smart biomaterials may use internal or external stimuli as triggering mechanisms. Internal stimuli-responsive smart biomaterials include those that respond to specific enzymes or changes in microenvironment pH; external stimuli can consist of electromagnetic, light, or acoustic energy; with some smart biomaterials responding to multiple stimuli. This review looks at current and evolving stimuli-responsive polymeric biomaterials in their proposed applications.

pH-dependent and cathepsin B activable CaCO3 nanoprobe for targeted in vivo tumor imaging

Background: The intraoperative visualization of tumor cells is a powerful modality for surgical treatment of solid tumors. Since the completeness of tumor excision is closely correlated with the survival of patients, probes that can assist in distinguishing tumor cells are highly demanded.

Purpose: In the present study, a fluorescent probe JF1 was synthesized for imaging of tumor cells by conjugating a substrate of cathepsin B (quenching moiety) to Oregon Green derivative JF2 using a self-immolative linker.

Methods: JF1 was then loaded into the folate-PEG modified CaCO₃ nanoparticles. The folate receptor-targeted, pH-dependent, and cathepsin B activable CaCO₃ nanoprobe was test in vitro and in vivo for tumor imaging.

Results: CaCO₃ nanoprobe demonstrated good stability and fast lighting ability in tumors under low pH conditions. It also showed lower fluorescence background than the single cathepsin B dependent fluorescent probe. The pH-dependent and cathepsin B controlled “turn-on” property enables precise and fast indication of tumor in vitro and in vivo.

Conclusion: This strategy of controlled drug delivery enables in vivo imaging of tumor nodules with a high signal-to-noise ratio, which has great potential in surgical tumor treatment.

A novel fluorescent surfactant enhances the delivery of the Cas9 ribonucleoprotein and enables the identification of edited cells

In this report, we designed and synthesized a novel fluorescent single tailed surfactant (termed FEDS), which can disrupt endosomes, complex lipofectamine, and can also identify cells that have been transfected. FEDS was able to increase the gene editing efficiency of lipofectamine/Cas9 ribonucleoprotein by 300% via a combination of fluorescent based enrichment and endosomal disruption.

d-Glucose recognition based on phenylboronic acid-functionalized polyoligomeric silsesquioxane fluorescent probe

We report a new strategy to synthesize hybrid fluorescent nanosensors consisting of phenylboronic acid-functionalized POSS (POSS-PBA) and diol-modified 8-anilino-1-naphthalenesulfonic acid (ANSA (a fluorescent dye)) for the detection of the biologically important d-glucose. The probe was characterized by FT-IR and ¹H NMR analyses, and the photoluminescence intensity was measured under various conditions to confirm its glucose sensing ability. Our POSS-APBA-dye probe could detect glucose at concentrations of 0-20 mg/mL, with a good linear relationship even at low glucose concentrations of 0-1 mg/mL. The properties of the POSS-APBA-dye probe were evaluated and compared with those of an APBA-dye probe. The glucose sensing ability of our POSS-APBA-dye probe was largely unaffected by the presence of interfering substances. The probe showed high sensing ability in a pH 5 environment and long-term (approximately 40 days) fluorescence stability.

A non-conjugated polyethylenimine copolymer-based unorthodox nanoprobe for bioimaging and related mechanism exploration

A non-conjugated polyethylenimine copolymer-based nanoprobe for lysosome-specific staining and tumor-targeted bioimaging and related mechanism exploration.

Auto-fluorescent polymer nanotheranostics for self-monitoring of cancer therapy via triple-collaborative strategy

Aberrant regulation of angiogenesis supply sufficient oxygen and nutrients to exacerbate tumor progression and metastasis. Taking this hallmark of cancer into account, reported here is a self-monitoring and triple-collaborative therapy system by auto-fluorescent polymer nanotheranostics which could be concurrently against angiogenesis and tumor cell growth by combining the benefits of anti-angiogenesis, RNA interfere and photothermal therapy (PTT). Auto-fluorescent amphiphilic polymer polyethyleneimine-polylactide (PEI-PLA) with positive charge can simultaneously load hydrophobic antiangiogenesis agent combretastatin A4 (CA4), NIR dye IR825 and absorb negatively charged heat shock protein 70 (HSP70) inhibitor (siRNA against HSP70) to construct self-monitoring nanotheranostics (NPICS). NPICS can effectively restrain the expression of HSP70 to reduce their endurance to the IR825-mediated PTT, leading to an enhanced photocytotoxicity. In a xenograft mouse tumor model, NPICS show an effect of inhibition of tumor angiogenesis and also display a highly synergistic anticancer efficacy with NIR laser irradiation. Significantly, based on its inherent auto-fluorescence, PEI-PLA not only serves as the drug carrier, but also as the self-monitor to real-time track NPICS biodistribution and tumor accumulation via fluorescence imaging. Moreover, IR825 endows NPICS could also be used as photoacoustic (PA) agents for in vivo PA imaging. This nanoplatform shows enormous potentials in cancer theranostics.

Gadolinium-doped hollow CeO2-ZrO2 nanoplatform as multifunctional MRI/CT dual-modal imaging agent and drug delivery vehicle

Developing multifunctional nanoparticle-based theranostic platform for cancer diagnosis and treatment is highly desirable, however, most of the present theranostic platforms are fabricated via complicated structure/composition design and time-consuming synthesis procedures. Herein, the multifunctional Gd/CeO2-ZrO2/DOX-PEG nanoplatform with single nano-structure was fabricated through a facile route, which possessed MR/CT dual-model imaging and chemotherapy ability. The nanoplatform not only exhibited well-defined shapes, tunable compositions and narrow size distributions, but also presented a well anti-cancer effect and MR/CT imaging ability. Therefore, the Gd/CeO2-ZrO2/DOX-PEG nanoplatform could be applied for chemotherapy as well as dual-model MR/CT imaging.

A dual-targeting DNA tetrahedron nanocarrier for breast cancer cell imaging and drug delivery

To enhance efficacy of chemotherapy and achieve real-time imaging of cancer cells, it is crucial to develop nanocarriers with targeted drug delivery capacity and fluorescence property for cancer theranostics. Herein, a dual-targeting DNA tetrahedron nanocarrier (MUC1-Td-AS1411) was constructed for breast cancer cell imaging and targeted drug delivery. This nanocarrier consisted of three components: (i) DNA tetrahedron core for multivalent conjugation of function ligands and loading doxorubicin (Dox); (ii) activatable MUC1 aptamer probe (MUC1-probe), formed by the hybridization of MUC1 aptamer sequence with fluorophore extended from one vertex and complementary sequence with quencher, for targeting and imaging MUC1 protein on cytomembrane; (iii) AS1411 aptamer, which was hybridized to the overhang on three vertexes via prolonged sequence, for binding to nucleolin. Firstly, MUC1-probe of this nanocarrier targeted MUC1 protein of MUC1-positive cells, causing a conformational reorganization of MUC1 aptamer, releasing complementary sequence with quencher and leading to fluorescence recovery. Subsequently, after internalizing into cells, AS1411 aptamer moiety of nanocarrier bound to nucleolin selectively, then the whole nanocarrier targeted nucleus and released Dox into nucleus. MUC1-positive cells and MUC1-negative cells could be differentiated by means of fluorescence imaging. Versus free Dox, Dox-loaded MUC1-Td-AS1411 showed lower cytotoxicity to MUC1-negative HL-7702 cells (P < 0.01), approximately equal lethality to sensitive MCF-7 cells (P > 0.05) whereas more effective to doxorubicin-resistant MCF-7 cells (P < 0.01). Therefore, this nanocarrier could be used as a promising candidate for cancer theranostics.

Recent advances in iridium(iii) complex-assisted nanomaterials for biological applications

Phosphorescent iridium(iii) complexes have gained increasing attention in biological applications owing to their excellent photophysical properties and efficient transportation into live cells.

CO2-Acidolysis of iminoboronate ester based polymersomes

The iminoboronate-terminalized star-like prodrug N₃-(OEG-IBCAPE)₄ was prepared to investigate the CO₂-acidolysis of polymersomes with a tunable release feature of CAPE molecules.

Temperature responsive fluorescent polymer nanoparticles (TRFNPs) for cellular imaging and controlled releasing of drug to living cells

Recent studies have demonstrated that drug delivery by using functional nanomaterials with imaging capability could afford plenty of insightful information for the better control of the delivery process. In this work, we developed temperature responsive fluorescent nanoparticles (TRFNPs) for drug delivery and cellular imaging. The TRFNP was fabricated by one-pot co-precipitation of thermal sensitive amphiphilic block copolymers polystyrene-b-poly(N-isopropyl acrylamide) (PS-b-PNIPAM) and fluorescent conjugated polymer poly [(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo(2,1',3)-thiadiazole)] (PFBT) in the presence of desired small guest molecules. The dynamic light scattering (DLS) measurements verified that this functional nanoparticle exhibited temperature dependent size variation, which could therefore regulate the releasing rate of loaded guest molecules (e.g. drugs) inside the polymer core. Besides, the TRFNPs displayed good photostability in terms of optical characterization. The cellular cytotoxicity characterization demonstrated that this nanoparticle exhibited good biocompatibility even under the mass concentration of 10μg/mL. By using Nile Red as a model molecule, the temperature-controlled releasing process from TRFNPs in solution as well as inside living cells was monitored directly according to the spectroscopic and microscopic characterizations. Furthermore, anti-cancer drug was successfully delivered into living cells via TRFNPs and released in a temperature dependent manner. As a consequence, owing the attractive merits as mentioned above, this nanostructure would find broad applications in nanomedicine in the future.

In Situ Monitoring Intracellular Structural Change of Nanovehicles through Photoacoustic Signals Based on Phenylboronate-Linked RGD-Dextran/Purpurin 18 Conjugates

The stimuli-responsive polymeric nanocarriers have been studied extensively, and their structural changes in cells are important for the controlled intracellular drug release. The present work reported RGD-dextran/purpurin 18 conjugates with pH-responsive phenylboronate as spacer for monitoring the structural change of nanovehicles through ratiometric photoacoustic (PA) signal. Phenylboronic acid modified purpurin 18 (NPBA-P18) could attach onto the RGD-decorated dextran (RGD-Dex), and the resulting RGD-Dex/NPBA-P18 (RDNP) conjugates with different molar ratios of RGD-Dex and NPBA-P18 were prepared. When the moles of NPBA-P18 were equivalent to more than triple of RGD-Dex, the single-stranded RDNP conjugates could self-assemble into nanoparticles in aqueous solution due to the fairly strong hydrophobicity of NPBA-P18. The pH-responsive aggregations of NPBA-P18 were investigated by UV-vis, fluorescence, and circular dichroism spectra, as well as transmission electron microscope. Based on distinct PA signals between monomeric and aggregated state, ratiometric PA signal of I₇₅₀/I₇₁₀ could be presented to trace the structural change progress. Compared with RDNP single chains, the nanoparticles exhibited effective cellular internalization through endocytosis pathway. Furthermore, the nanoparticles could form well-ordered aggregates responding to intracellular acidic environment, and the resulting structural change was also monitored by ratiometric PA signal. Therefore, the noninvasive PA approach could provide a deep insight into monitoring the intracellular structural change process of stimuli-responsive nanocarriers.

A two-photon-activated prodrug for therapy and drug release monitoring

A two-photon-activated prodrug has been developed for drug release monitoring and photo-controllable therapy.

Using hyaluronic acid-functionalized pH stimuli-responsive mesoporous silica nanoparticles for targeted delivery to CD44-overexpressing cancer cells

In this study, novel hyaluronic acid-pH stimuli-responsive lipid membrane mesoporous silica nanoparticles (HA-PL-MSNs) were designed and assembled, with the chemotherapeutic agent doxorubicin (DOX) as the model drug. HA-PL-MSNs exhibited a well-defined mesostructure covered by lipid bilayer and particle size of ~150 nm. The drug loading capacity was up to ~18.2%. DOX release could be effectively retained by the lipid bilayer in pH 7.4 buffer and exhibited a pH-triggered burst release in the acidic condition. Confocal laser scanning microscopy and fluorescence-activated cell sorting showed that HA-PL-MSNs exhibited higher cellular uptake efficiency via CD44 receptor-mediated endocytosis compared with PL-MSNs in HeLa cells. In vitro cytotoxicity studies demonstrated that HA-PL-MSNs could effectively enhance the targeted delivery of DOX and restrain the growth of HeLa cells. This might provide a promising alternative for the development of a targeted anticancer drug delivery system.

Triple Redox Responsive Poly(Ethylene Glycol)-Polycaprolactone Polymeric Nanocarriers for Fine-Controlled Drug Release

Stimuli-responsive nanocarriers with the ability to respond to tumorous heterogeneity have been extensively developed for drug delivery. However, the premature release during blood circulation and insufficient intracellular drug release are still a significant issue. Herein, three disulfide bonds are introduced into the amphiphilic poly(ethylene glycol)-polycaprolactone copolymer blocks to form triple-sensitive cleavable polymeric nanocarrier (tri-PESC NPs) to improve its sensitivity to narrow glutathione (GSH) concentration. The tri-PESC NPs keep intact during blood circulation due to the limited cleaving of triple-disulfide bonds, whereas the loaded drug is efficiently released at tumor cells with the increased concentration of GSH. In vitro studies of doxorubicin-loaded tri-PESC NPs show that the nanocarriers achieve sufficient drug release in cancerous cells and inhibit the tumor cells growth, though they only bring minimum damage to normal cells. Therefore, the tri-PESC NPs with triple-sensitive cleavable bonds hold great promise to improve the therapeutic index in cancer therapy.

Carboxymethyl Dextran-Stabilized Polyethylenimine-Poly(epsilon-caprolactone) Nanoparticles-Mediated Modulation of MicroRNA-34a Expression via Small-Molecule Modulator for Hepatocellular Carcinoma Therapy

MicroRNA-34a (miR-34a) modulation therapy has shown great promise to treat hepatocellular carcinoma (HCC). 2'-Hydroxy-2,4,4',5,6'-pentamethoxychalcone, termed Rubone, has been shown to specifically upregulate miR-34a expression in HCC cells and considered as novel anticancer agent. However, the extremely low aqueous solubility of Rubone hampers its use in cancer treatment. In the present study, surface-stabilized nanoparticles-based delivery strategy was engaged to overcome this impediment. In our preparation, Rubone was encapsulated in the micelles composed of polyethylenimine-poly(epsilon-caprolactone) (PEI-PCL) through hydrophobic interactions, which were subsequently stabilized with anionic carboxymethyl dextran CMD via electronic interaction. We found that Rubone-encapsulating nanoparticles are dispersed well in aqueous solution. The results further demonstrated that Rubone could be efficiently delivered in HCC cells by nanoparticles and upregulate miR-34a expression, which in turn led to inhibition of proliferation, migration, and increased apoptosis of HCC cells. In vivo experiments showed that Rubone can be preferentially delivered into tumor tissues by CMD-stabilized PEI-PCL nanoparticles after intravenous administration and significantly inhibited tumor growth. Furthermore, low cytotoxicity of the nanoparticles was observed in vitro and in vivo analyses, indicating a good compatibility of generated nanoparticles. The obtained results suggest that CMD-stabilized PEI-PCL nanoparticles may serve as a novel approach for small-molecule-modulator-mediated miR-34a restoration for HCC therapy.

Stimulus responsive nanogel with innate near IR fluorescent capability for drug delivery and bioimaging

A brighter, non toxic and biocompatible optical imaging agent is one of the major quests of biomedical research. Here in, we report a photoluminescent comacromer [PEG-poly(propylene fumarate)-citric acid-glycine] and novel stimulus (pH) responsive nanogel endowed with excitation wavelength dependent fluorescence (EDF) for combined drug delivery and bioimaging applications. The comacromer when excited at different wavelengths in visible region from 400nm to 640nm exhibits fluorescent emissions from 510nm to 718nm in aqueous condition. It has high Stokes shift (120nm), fluorescent lifetime (7 nanoseconds) and quantum yield (50%). The nanogel, C-PLM-NG, prepared with this photoluminescent comacromer and N,N-dimethyl amino ethylmethacrylate (DMEMA) has spherical morphology with particle size around 100nm and 180nm at pH 7.4 (physiological) and 5.5 (intracellular acidic condition of cancer cells) respectively. The studies on fluorescence characteristics of C-PLM NG in aqueous condition reveal large red-shift with emissions from 523nm to 700nm for excitations from 460nm to 600nm ascertaining the EDF characteristics. Imaging the near IR emission with excitation at 535nm was accomplished using cut-off filters. The nanogel undergoes pH responsive swelling and releases around 50% doxorubicin (DOX) at pH 5.5 in comparison with 15% observed at pH 7.4. The studies on in vitro cytotoxicity with MTT assay and hemolysis revealed that the present nanogel is non-toxic. The DOX-loaded C-PLM-NG encapsulated in Hela cells induces lysis of cancer cells. The inherent EDF characteristics associated with C-PLM NG enable cellular imaging of Hela cells. The studies on biodistribution and clearance mechanism of C-PLM-NG from the body of mice reveal bioimaging capability and safety of the present nanogel. This is the first report on a polymeric nanogel with innate near IR emissions for bioimaging applications.

Selenium-containing organic nanoparticles as silent precursors for ultra-sensitive thiol-responsive transmembrane anion transport

An anion transporter with a selenoxide group was able to form nanoparticles in water, whose activity was fully turned off due to the aggregation effect. The formed nanoparticles have a uniform size and can be readily dispersed in water at high concentrations. Turn-on of the nanoparticles by reducing molecules is proposed to be a combined process, including the reduction of selenoxide to selenide, disassembly of the nanoparticles and location of the transporter to the lipid membrane. Accordingly, a special acceleration phase can be observed in the turn-on kinetic curves. Since turn-on of the nanoparticles is quantitatively related to the amount of reductant, the nanoparticles can be activated in a step-by-step manner. Due to the sensibility of this system to thiols, cysteine can be detected at low nanomolar concentrations. This ultra-sensitive thiol-responsive transmembrane anion transport system is quite promising in biological applications.

How tubular aggregates interact with biomembranes: wrapping, fusion and pearling

How soft tubular aggregates interact with biomembranes is crucial for understanding the formation of membrane tubes connecting two eukaryotic cells, which are initially created from one cell and then connect with the other.

CO2/pH-responsive particles with built-in fluorescence read-out

A novel fluorescent monomer was synthesized to probe the state of CO₂-responsive cross-linked polymer particles.

Dynamism of Stimuli-Responsive Nanohybrids: Environmental Implications

Nanomaterial science and design have shifted from generating single passive nanoparticles to more complex and adaptive multi-component nanohybrids. These adaptive nanohybrids (ANHs) are designed to simultaneously perform multiple functions, while actively responding to the surrounding environment. ANHs are engineered for use as drug delivery carriers, in tissue-engineered templates and scaffolds, adaptive clothing, smart surface coatings, electrical switches and in platforms for diversified functional applications. Such ANHs are composed of carbonaceous, metallic or polymeric materials with stimuli-responsive soft-layer coatings that enable them to perform such switchable functions. Since ANHs are engineered to dynamically transform under different exposure environments, evaluating their environmental behavior will likely require new approaches. Literature on polymer science has established a knowledge core on stimuli-responsive materials. However, translation of such knowledge to environmental health and safety (EHS) of these ANHs has not yet been realized. It is critical to investigate and categorize the potential hazards of ANHs, because exposure in an unintended or shifting environment could present uncertainty in EHS. This article presents a perspective on EHS evaluation of ANHs, proposes a principle to facilitate their identification for environmental evaluation, outlines a stimuli-based classification for ANHs and discusses emerging properties and dynamic aspects for systematic EHS evaluation.

Glutathione- and pH-responsive nonporous silica prodrug nanoparticles for controlled release and cancer therapy

A myriad of drug delivery systems such as liposomes, micelles, polymers and inorganic nanoparticles (NPs) have been developed for cancer therapy. Very few of them, however, have the ability to integrate multiple functionalities such as specific delivery, high circulation stability, controllable release and good biocompatibility and biodegradability in a single system to improve the therapeutic efficacy. Herein, we report two types of stimuli-responsive nonporous silica prodrug NPs towards this goal for controlled release of anticancer drugs and efficient combinatorial cancer therapy. As a proof of concept, anticancer drugs camptothecin (CPT) and doxorubicin (DOX) were covalently encapsulated into silica matrices through glutathione (GSH)-responsive disulfide and pH-responsive hydrazone bonds, respectively, resulting in NPs with sizes tunable in the range of 50-200 nm. Both silica prodrug NPs showed stimuli-responsive controlled release upon exposure to a GSH-rich or acidic environment, resulting in improved anticancer efficacy. Notably, two prodrug NPs simultaneously taken up by HeLa cells showed a remarkable combinatorial efficacy compared to free drug pairs. These results suggest that the stimuli-responsive silica prodrug NPs are promising anticancer drug carriers for efficient cancer therapy.