Super-Cationic Carbon Quantum Dots Synthesized from Spermidine as an Eye Drop Formulation for Topical Treatment of Bacterial Keratitis

We have developed a one-step method to synthesize carbon quantum dots (CQD_PAs) from biogenic polyamines (PAs) as an antibacterial agent for topical treatment of bacterial keratitis (BK). CQDs synthesized by direct pyrolysis of spermidine (Spd) powder through a simple dry heating treatment exhibit a solubility and yield much higher than those from putrescine and spermine. We demonstrate that CQDs obtained from Spds (CQD_Spds) possess effective antibacterial activities against non-multidrug-resistant Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Salmonella enterica serovar Enteritidis bacteria and also against the multidrug-resistant bacteria, methicillin-resistant S. aureus. The minimal inhibitory concentration (MIC) of CQD_Spds is ∼2500-fold lower than that of spermidine alone, demonstrating their strong antibacterial capabilities. Investigation of the possible mechanisms behind the antibacterial activities of the as-synthesized CQD_Spds indicates that the super-cationic CQD_Spds with small size (diameter ca. 6 nm) and highly positive charge (ζ-potential ca. +45 mV) cause severe disruption of the bacterial membrane. In vitro cytotoxicity, hemolysis, hemagglutination, genotoxicity, and oxidative stress and in vivo morphologic and physiologic cornea change evaluations show the good biocompatibility of CQD_Spds. Furthermore, topical ocular administration of CQD_Spds can induce the opening of the tight junction of corneal epithelial cells, thereby leading to great antibacterial treatment of S. aureus-induced BK in rabbits. Our results suggest that CQD_Spds are a promising antibacterial candidate for clinical applications in treating eye-related bacterial infections and even persistent bacteria-induced infections.

A review on nanostructured carbon quantum dots and their applications in biotechnology, sensors, and chemiluminescence

Carbon quantum dots (CQDs) are a member of carbon nanostructures family which have received increasing attention for their photoluminescence (PL), physical and chemical stability and low toxicity. The classical semiconductor quantum dots (QDs) are semiconductor particles that are able to emit fluorescence by excitation. The CQDs is mainly referred to photoluminescent carbon nanoparticles less than 10 nm, with surface modification or functionalization. Contrary to other carbon nanostructures, CQDs can be synthesized and functionalized fast and easily. The fluorescence origin of the CQDs is a controversial issue which depends on carbon source, experimental conditions, and functional groups. However, PL emissions originated from conjugated π-domains and surface defects have been proposed for the PL emission mechanisms of the CQDs. These nanostructures have been used as nontoxic alternatives to the classical heavy metals containing semiconductor QDs in some applications such as in-vivo and in-vitro bio-imaging, drug delivery, photosensors, chemiluminescence (CL), and etc. This paper will introduce CQDs, their structure, and PL characteristics. Recent advances of the application of CQDs in biotechnology, sensors, and CL is comprehensively discussed.

Carbon Dots as Potent Antimicrobial Agents

Carbon dots (CDots) have emerged to represent a highly promising new platform for visible/natural light-activated microbicidal agents. In this article, the syntheses, structures, and properties of CDots are highlighted, representative studies on their activities against bacteria, fungi, and viruses reviewed, and the related mechanistic insights discussed. Also highlighted and discussed are the excellent opportunities for potentially extremely broad applications of this new platform, including theranostics uses.

Stimuli-Responsive "Cluster Bomb" for Programmed Tumor Therapy

In this paper, mesoporous silica nanoparticle (MSN) loaded with doxorubicin (DOX) and capped with tumor-homing/-penetrating peptide tLyP-1-modified tungsten disulfide quantum dots (WS₂-HP) was designed and applied as a stimuli-responsive "Cluster Bomb" for high-performance tumor suppression. The peptide tLyP-1 on the surface can both facilitate the homing of DOX@MSN-WS₂-HP to 4T1 tumor and greatly enhance the penetration of WS₂-HP in tumor. The benzoic-imine bonds as the linkers between "bomblets" and "dispenser" are stable under normal physical conditions and quite labile at pH 6.8. After arriving at the mild acidic tumor microenvironment, the nanoplatform can rapidly break into two parts: (1) electropositive DOX@MSN-NH₂ for efficient chemotherapy on surface tumor cells and (2) small-sized WS₂-HP with improved tumor penetrating ability for near-infrared (NIR)-light-triggered photothermal therapy (PTT) among deep-seated tumor cells. Having killed the tumor cells in different depths, DOX@MSN-WS₂-HP exhibited significant antitumor effect, which will find great potential in clinical trials.

Subretinally injected semiconducting polymer nanoparticles rescue vision in a rat model of retinal dystrophy

Inherited retinal dystrophies and late-stage age-related macular degeneration, for which treatments remain limited, are among the most prevalent causes of legal blindness. Retinal prostheses have been developed to stimulate the inner retinal network; however, lack of sensitivity and resolution, and the need for wiring or external cameras, have limited their application. Here we show that conjugated polymer nanoparticles (P3HT NPs) mediate light-evoked stimulation of retinal neurons and persistently rescue visual functions when subretinally injected in a rat model of retinitis pigmentosa. P3HT NPs spread out over the entire subretinal space and promote light-dependent activation of spared inner retinal neurons, recovering subcortical, cortical and behavioural visual responses in the absence of trophic effects or retinal inflammation. By conferring sustained light sensitivity to degenerate retinas after a single injection, and with the potential for high spatial resolution, P3HT NPs provide a new avenue in retinal prosthetics with potential applications not only in retinitis pigmentosa, but also in age-related macular degeneration.

Nanoscale artificial antigen presenting cells for T cell immunotherapy

Artificial antigen presenting cells (aAPC), which deliver stimulatory signals to cytotoxic lymphocytes, are a powerful tool for both adoptive and active immunotherapy. Thus far, aAPC have been synthesized by coupling T cell activating proteins such as CD3 or MHC-peptide to micron-sized beads. Nanoscale platforms have different trafficking and biophysical interaction properties and may allow development of new immunotherapeutic strategies. We therefore manufactured aAPC based on two types of nanoscale particle platforms: biocompatible iron-dextran paramagnetic particles (50-100 nm in diameter) and avidin-coated quantum dot nanocrystals (~30 nm). Nanoscale aAPC induced antigen-specific T cell proliferation from mouse splenocytes and human peripheral blood T cells. When injected in vivo, both iron-dextran particles and quantum dot nanocrystals enhanced tumor rejection in a subcutaneous mouse melanoma model. This is the first description of nanoscale aAPC that induce antigen-specific T cell proliferation in vitro and lead to effective T cell stimulation and inhibition of tumor growth in vivo.

FROM THE CLINICAL EDITOR

Artifical antigen presenting cells could revolutionize the field of cancer-directed immunotherapy. This team of investigators have manufactured two types of nanoscale particle platform-based aAPCs and demonstrates that both iron-dextran particles and quantum dot nanocrystals enhance tumor rejection in a melanoma model, providing the first description of nanoscale aAPCs that lead to effective T cell stimulation and inhibition of tumor growth.

Aspirin-Based Carbon Dots, a Good Biocompatibility of Material Applied for Bioimaging and Anti-Inflammation

The emerging photoluminescent carbon-based nanomaterials are promising in various fields besides cell imaging and carrier transport. Carbon nanomaterials with specific biological functions, however, are rarely investigated. Aspirin is a very common anti-inflammatory medication to relieve aches and pains. In this study, we have tried to create a carbon nanoparticle with aspirin, and we expect that this new carbon nanoparticle will have both anti-inflammatory and fluorescent biomarker functions. Fluorescent aspirin-based carbon dots (FACDs) were synthesized by condensing aspirin and hydrazine through a one-step microwave-assisted method. Imaging data demonstrated that FACDs efficiently entered into human cervical carcinoma and mouse monocyte macrophage cells in vitro with low cell toxicity. Results from quantitative polymerase chain reaction and histological analysis indicated that FACDs possessed effective anti-inflammatory effects in vitro and in vivo compared to aspirin only. Hematology, serum biochemistry, and histology results suggested that FACDs also had no significant toxicity in vivo. Our results clearly demonstrate that FACDs have dual functions, cellular imaging/bioimaging and anti-inflammation, and suggest that FACDs have great potential in future clinical applications.

Fluorescent carbon dots as an efficient siRNA nanocarrier for its interference therapy in gastric cancer cells

BACKGROUND

Fluorescent carbon dots (Cdots) have attracted increasing attention due to their potential applications in sensing, catalysis, and biomedicine. Currently, intensive research has been concentrated on the synthesis and imaging-guided therapy of these benign photoluminescent materials. Meanwhile, Cdots have been explored as nonviral vector for nucleic acid or drug delivery by chemical modification on purpose.

RESULTS

We have developed a microwave assisted one-step synthesis of Cdots with citric acid as carbon source and tryptophan (Trp) as both nitrogen source and passivation agent. The Cdots with uniform size show superior water solubility, excellent biocompatibility, and high quantum yield. Afterwards, the PEI (polyethylenimine)-adsorbed Cdots nanoparticles (Cdots@PEI) were applied to deliver Survivin siRNA into human gastric cancer cell line MGC-803. The results have confirmed the nanocarrier exhibited excellent biocompatibility and a significant increase in cellular delivery of siRNA, inducing efficient knockdown for Survivin protein to 6.1%. In addition, PEI@Cdots complexes mediated Survivin silencing, the arrested cell cycle progression in G1 phase as well as cell apoptosis was observed.

CONCLUSION

The Cdots-based and PEI-adsorbed complexes both as imaging agents and siRNA nanocarriers have been developed for Survivin siRNA delivery. And the results indicate that Cdots-based nanocarriers could be utilized in a broad range of siRNA delivery systems for cancer therapy.

Phototherapy-based combination strategies for bacterial infection treatment

The development of nanomedicine is expected to provide an innovative direction for addressing challenges associated with multidrug-resistant (MDR) bacteria. In the past decades, although nanotechnology-based phototherapy has been developed for antimicrobial treatment since it rarely causes bacterial resistance, the clinical application of single-mode phototherapy has been limited due to poor tissue penetration of light sources. Therefore, combinatorial strategies are being developed. In this review, we first summarized the current phototherapy agents, which were classified into two functional categories: organic phototherapy agents (e.g., small molecule photosensitizers, small molecule photosensitizer-loaded nanoparticles and polymer-based photosensitizers) and inorganic phototherapy agents (e.g., carbo-based nanomaterials, metal-based nanomaterials, composite nanomaterials and quantum dots). Then the development of emerging phototherapy-based combinatorial strategies, including combination with chemotherapy, combination with chemodynamic therapy, combination with gas therapy, and multiple combination therapy, are presented and future directions are further discussed. The purpose of this review is to highlight the potential of phototherapy to deal with bacterial infections and to propose that the combination therapy strategy is an effective way to solve the challenges of single-mode phototherapy.

Nonendocytic delivery of functional engineered nanoparticles into the cytoplasm of live cells using a novel, high-throughput microfluidic device

The ability to straightforwardly deliver engineered nanoparticles into the cell cytosol with high viability will vastly expand the range of biological applications. Nanoparticles could potentially be used as delivery vehicles or as fluorescent sensors to probe the cell. In particular, quantum dots (QDs) may be used to illuminate cytosolic proteins for long-term microscopy studies. Whereas recent advances have been successful in specifically labeling proteins with QDs on the cell membrane, cytosolic delivery of QDs into live cells has remained challenging. In this report, we demonstrate high throughput delivery of QDs into live cell cytoplasm using an uncomplicated microfluidic device while maintaining cell viabilities of 80-90%. We verify that the nanoparticle surface interacts with the cytosolic environment and that the QDs remain nonaggregated so that single QDs can be observed.

Photocatalysis Enhancement for Programmable Killing of Hepatocellular Carcinoma through Self-Compensation Mechanisms Based on Black Phosphorus Quantum-Dot-Hybridized Nanocatalysts

Recently reported black phosphorus quantum dots (BPQDs) possess unique photocatalysis activities. However, the environmental instability accompanied by a hypoxic tumor microenvironment (TME) seriously hindered the bioapplications of BPQDs, especially in oxygen-dependent photodynamic therapy (PDT). Here, we construct a hepatocellular carcinoma (HCC)-specific targeting aptamer "TLS11a"-decorated BPQDs-hybridized nanocatalyst, which can specifically target HCC tumor cells and self-compensate oxygen (O2) into hypoxic TME for enhancing PDT efficiency. The BPQD-hybridized mesoporous silica framework (BMSF) with in situ synthesized Pt nanoparticles (PtNPs) in the BMSF is simply prepared. After being decorated by TLS11a aptamer/Mal-PEG-NHS, the resultant nanosystem (refer as Apt-BMSF@Pt) exhibits excellent environmental stability, active targeting ability to HCC cells, and self-compensation ability of oxygen. Compared with the PEG-BMSF@Pt without H2O2 incubation, the PEG-BMSF@Pt nanocatalyst exhibits 4.2-folds O2 and 1.6-folds 1O2 generation ability in a mimetic closed-system in the presence of both H2O2 and near-infrared laser. In a mouse model, the Apt-BMSF@Pt can effectively accumulate into tumor sites, and the core of BMSF subsequently can act as a photosensitizer to generate reactive oxygen species, while the PtNPs can serve as a catalyst to convert H2O2 into O2 for enhancing PDT through self-compensation mechanisms in hypoxic TME. By comparison of the tumor volume/weight, H&E, and immunohistochemical analysis, the excellent antitumor effects with minimized side effects of our Apt-BMSF@Pt could be demonstrated in vivo. Taken together, the current study suggests that our Apt-BMSF@Pt could act as an active targeting nanocatalyst for programmable killing of cancer cells in hypoxic TME.

Multifunctional N-P-doped carbon dots for regulation of apoptosis and autophagy in B16F10 melanoma cancer cells and in vitro imaging applications

Rationale: The present study reports the multifunctional anticancer activity against B16F10 melanoma cancer cells and the bioimaging ability of fluorescent nitrogen-phosphorous-doped carbon dots (NPCDs). Methods: The NPCDs were synthesized using a single-step, thermal treatment and were characterized by TEM, XPS, fluorescence and UV-Vis spectroscopy, and FTIR analysis. The anticancer efficacy of NPCDs was confirmed by using cell viability assay, morphological evaluation, fluorescent live-dead cell assay, mitochondrial potential assay, ROS production, RT-PCR, western-blot analysis, siRNA transfection, and cellular bioimaging ability. Results: The NPCDs inhibited the proliferation of B16F10 melanoma cancer cells after 24 h of treatment and induced apoptosis, as confirmed by the presence of fragmented nuclei, reduced mitochondrial membrane potential, and elevated levels of reactive oxygen species. The NPCDs treatment further elevated the levels of pro-apoptotic factors and down-regulated the level of Bcl2 (B-cell lymphoma 2) that weakened the mitochondrial membrane, and activated proteases such as caspases. Treatment with NPCDs also resulted in dose-dependent cell cycle arrest, as indicated by reduced cyclin-dependent kinase (CDK)-2, -4, and -6 protein levels and an enhanced level of p21. More importantly, the NPCDs induced the activation of autophagy by upregulating the protein expression levels of LC3-II and ATG-5 (autophagy-related-5) and by downregulating p62 level, validated by knockdown of ATG-5. Additionally, owing to their excellent luminescence property, these NPCDs were also applicable in cellular bioimaging, as evidenced by the microscopic fluorescence imaging of B16F10 melanoma cells. Conclusion: Based on these findings, we conclude that our newly synthesized NPCDs induced cell cycle arrest, autophagy, and apoptosis in B16F10 melanoma cells and presented good cellular bioimaging capability.

In vivo monitoring of neural stem cells after transplantation in acute cerebral infarction with dual-modal MR imaging and optical imaging

Stem cell therapies are promising strategies for the treatment of stroke. However, their clinical translation has not been fully realized due, in part, to insufficient ability to track stem cell migration and survival longitudinally over long periods of time in vivo. In this work, we synthesized a new class of manometer-sized cationic polymersomes loaded with superparamagnetic iron oxide nanoparticles and quantum dots for in vivo dual-modal imaging of stem cells. The results demonstrated that the synthesized cationic polymersomes can act as an effective and safety carrier to transfer image labels into neural stem cells, upon which the distribution and migration of grafted stem cells could be monitored by MR imaging up to 6 weeks and by fluorescence imaging within 4 weeks in the context of ischaemic brain injury. Cationic polymersomes hold great promise in the longitudinal monitoring of transplanted stem cells by using dual-modal MRI and optical imaging.

Carbon dot cross-linked polyvinylpyrrolidone hybrid hydrogel for simultaneous dye adsorption, photodegradation and bacterial elimination from waste water

The creation of a polymeric hydrogel from polyvinylpyrrolidone (PVP) cross-linked by Carbon Quantum Dots (CD) for the adsorption and photocatalytic degradation of both cationic and anionic dyes. PVP, an important biocompatible constituent and often surplus in cosmetic industry, was carboxylated through NaOH refluxing and covalently conjugated to surface amine functionality of CD derived from lemon juice and Cysteamine. The hybrid hydrogel was obtained from PVP-CD covalent conjugate by careful manipulation of pH and found to possess better rheological properties than only carboxylate-PVP. The monolayer physisorption of the dyes on the hydrogel was affected by hydrogen bonding, dispersion or inductive effect, and π-π interaction with the polymer backbone as well as the CD that followed pseudo-second-order kinetics. Degradation of the adsorbed dyes was instated by the unique Reactive Oxygen Species (ROS) generating ability of the CD embedded in the hydrogel matrix upon exposure to sunlight, the mechanism of which is also unveiled. The same CD-induced ROS was found to effectively annihilate both gram-positive and gram-negative bacteria in real polluted water in less than 10 min of photoexcitation of the hydrogel. The hydrogel was restored by mild acid wash that is able to perform dye adsorption and photo-degradation upto four cycles.

A Multimodal System with Synergistic Effects of Magneto-Mechanical, Photothermal, Photodynamic and Chemo Therapies of Cancer in Graphene-Quantum Dot-Coated Hollow Magnetic Nanospheres

In this study, a multimodal therapeutic system was shown to be much more lethal in cancer cell killing compared to a single means of nano therapy, be it photothermal or photodynamic. Hollow magnetic nanospheres (HMNSs) were designed and synthesized for the synergistic effects of both magneto-mechanical and photothermal cancer therapy. By these combined stimuli, the cancer cells were structurally and physically destroyed with the morphological characteristics distinctively different from those by other therapeutics. HMNSs were also coated with the silica shells and conjugated with carboxylated graphene quantum dots (GQDs) as a core-shell composite: HMNS/SiO2/GQDs. The composite was further loaded with an anticancer drug doxorubicin (DOX) and stabilized with liposomes. The multimodal system was able to kill cancer cells with four different therapeutic mechanisms in a synergetic and multilateral fashion, namely, the magnetic field-mediated mechanical stimulation, photothermal damage, photodynamic toxicity, and chemotherapy. The unique nanocomposites with combined mechanical, chemo, and physical effects will provide an alternative strategy for highly improved cancer therapy efficiency.

Liposomal nanotheranostics for multimode targeted in vivo bioimaging and near-infrared light mediated cancer therapy

Developing a nanotheranostic agent with better image resolution and high accumulation into solid tumor microenvironment is a challenging task. Herein, we established a light mediated phototriggered strategy for enhanced tumor accumulation of nanohybrids. A multifunctional liposome based nanotheranostics loaded with gold nanoparticles (AuNPs) and emissive graphene quantum dots (GQDs) were engineered named as NFGL. Further, doxorubicin hydrochloride was encapsulated in NFGL to exhibit phototriggered chemotherapy and functionalized with folic acid targeting ligands. Encapsulated agents showed imaging bimodality for in vivo tumor diagnosis due to their high contrast and emissive nature. Targeted NFGL nanohybrids demonstrated near infrared light (NIR, 750 nm) mediated tumor reduction because of generated heat and Reactive Oxygen Species (ROS). Moreover, NFGL nanohybrids exhibited remarkable ROS scavenging ability as compared to GQDs loaded liposomes validated by antitumor study. Hence, this approach and engineered system could open new direction for targeted imaging and cancer therapy.

A novel and facile synthesis of porous SiO2-coated ultrasmall Se particles as a drug delivery nanoplatform for efficient synergistic treatment of cancer cells

A novel and facile synthetic route has been developed to fabricate porous SiO2-coated ultrasmall Se particles (Se@SiO2 nanospheres) as a drug delivery nanoplatform which combines Se quantum dots and doxorubicin (DOX) for efficient synergistic treatment of cancer cells.

Threshold Dose of Three Types of Quantum Dots (QDs) Induces Oxidative Stress Triggers DNA Damage and Apoptosis in Mouse Fibroblast L929 Cells

Although it has been reported that fluorescent quantum dots (QDs) have obvious acute toxic effects in vitro, their toxic effects at low doses or threshold doses are still unknown. Therefore, we evaluated the biological histocompatibility and in vitro toxicity of three types of QDs at threshold doses. Also, we compared the toxic effects of QDs with different raw chemical compositions and sizes. The results showed that low concentrations of QDs (≤7 μg/mL) had no obvious effect on cell viability and cell membrane damage, oxidative damage, cell apoptosis or DNA damage. However, QD exposure led to a significant cytotoxicity at higher doses (≥14 μg/mL) and induced abnormal cellular morphology. In addition, when comparing the three types of QDs, 2.2 nm CdTe QDs exposure showed a significantly increased proportion of apoptotic cells and significant DNA damage, suggesting that size and composition contribute to the toxic effects of QDs. Based on these discussions, it was concluded that the concentration (7 μg/mL) may serve as a threshold level for these three types of QDs only in L929 fibroblasts, whereas high concentrations (above 14 μg/mL) may be toxic, resulting in inhibition of proliferation, induction of apoptosis and DNA damage in L929 fibroblasts.

Multistage delivery of CDs-DOX/ICG-loaded liposome for highly penetration and effective chemo-photothermal combination therapy

Nanoparticles (NPs) have proven to be effective drug carriers in diagnosis and therapy of cancer. But, they faced a contradictory issue that NPs with large size appear weak tumor penetration, meanwhile small size resulted in poor tumor retention. Herein, we fabricated doxorubicin conjugated carbon dots (CDs-DOX) and indocyanine green (ICG)-loaded liposomes (ICG-LPs) named CDs-ICG-LPs using a modified reverse phase evaporation process, and with high incorporation in the aqueous core. The CDs-ICG-LPs exhibited good monodispersity, excellent fluorescence/size stability, and consistent spectra characteristics compared with free ICG or DOX. Moreover, the CDs-ICG-LPs showed higher temperature response, faster DOX release under laser irradiation. In the meantime, the fluorescence of DOX and ICG in CDs-ICG-LPs was also visualized for the process of subcellular location in vitro. In comparison with chemo or photothermal treatment alone, the combined treatment of CDs-ICG-LPs with laser irradiation synergistically induced the apoptosis and death of DOX-sensitive HepG2 cells. In vivo antitumor activities demonstrated CDs-ICG-LPs could reach higher antitumor activity compared with CDs-DOX and ICG-LPs for H22 tumor cells, and suppressed H22 tumor growth in vivo. Notably, no systemic toxicity occurrence was observed after repeated dose of CDs-ICG-LPs with laser irradiation. Hence, the well-defined CDs-ICG-LPs exhibited great potential in targeting cancer imaging and chemo-photothermal therapy.

Synthesis of multimodal polymersomes for targeted drug delivery and MR/fluorescence imaging in metastatic breast cancer model

The objective of the current study is to design and delivery of targeted PEG-PCL nanopolymersomes encapsulated with Gadolinium based Quantum Dots (QDs) and Doxorubicin (DOX) as magnetic resonance-florescence imaging and anti-cancer agent. Diagnostic and therapeutic efficiency of the prepared theranostic formulation was evaluated in vitro and in vivo. Hydrophobic QDs based on indium-copper-gadolinium-zinc sulfide were synthesized and characterized extensively. Hydrophobic QDs and hydrophilic DOX were loaded in PEG-PCL polymersomes through double emulsion method. Drug release pattern was studied in both citrate (pH 5.4) and phosphate (pH 7.4) buffer during 10 days. Both fluorescence and magnetic properties of bare QDs and prepared formulations were studied entirely. AS1411 DNA aptamer was covalently attached to the surface of polymersomal formulation in order to prepare targeted drug delivery system. Cellular cytotoxicity and cellular uptake analysis were performed in both nucleolin positive (MCF7 and 4T1) and nucleolin negative (CHO) cell lines. After in vitro evaluations, anti-tumor efficiency and diagnostic capability of the formulation was investigated in 4T1 tumor baring mice. Scanning emission electron microscopy (SEM) confirmed spherical shape and around 100 nm size of prepared formulations. Transmission electron microscopy (HRTEM) showed crystal shape of QDs with size of 2-3 nm. Drug release study obtained controlled release of encapsulated DOX and stability of formulation in physiologic condition. MTT and flow cytometry results demonstrated that AS1411 aptamer could enhance both toxicity and cellular uptake in nucleolin overexpressing cell lines (P < 0.05). Moreover, aptamer targeted formulation could increase survival rate and tumor inhibitory growth effect in 4T1 tumor baring mice (P < 0.05). Our results verify that aptamer targeted polymersomes loaded with non-toxic QDs as a diagnostic agent and DOX as an anti-cancer drug, could provide a theranostic platform with the purpose of optimization of treatment process and minimization of systemic side effects.

Rapid Intestinal Uptake and Targeted Delivery to the Liver Endothelium Using Orally Administered Silver Sulfide Quantum Dots

Quantum dots (QDs) are used for imaging and transport of therapeutics. Here we demonstrate rapid absorption across the small intestine and targeted delivery of QDs with bound materials to the liver sinusoidal endothelial cells (LSECs) or hepatocytes in vitro and in vivo following oral administration. QDs were radiolabeled with ³H-oleic acid, with a fluorescent tag or ¹⁴C-metformin placed within a drug binding site. Three different biopolymer shell coatings were compared (formaldehyde-treated serum albumin (FSA), gelatin, heparin). Passage across the small intestine into mesenteric veins is mediated by clathrin endocytosis and micropinocytosis. 60% of an oral dose of QDs was rapidly distributed to the liver within 30 min, and this increased to 85% with FSA biopolymer coating. Uptake into LSECs also increased 3-fold with FSA coating, while uptake into hepatocytes was increased from 40% to 85% with gelatin biopolymer coating. Localization of QDs to LSECs was confirmed with immunofluorescence and transmission electron microscopy. 85% of QDs were cleared within 24 h of administration. The bioavailability of ¹⁴C-metformin 2 h post-ingestion was increased 5-fold by conjugation with QD-FSA, while uptake of metformin into LSECs was improved 50-fold by using these QDs. Endocytosis of QDs by SK-Hep1 cells (an LSEC immortal cell line) was via clathrin- and caveolae-mediated pathways with QDs taken up into lysosomes. In conclusion, we have shown high specificity targeting of the LSEC or hepatocytes after oral administration of QDs coated with a biopolymer layer of FSA or gelatin, which improved the bioavailability and delivery of metformin to LSECs.

Comparative Study on the Efficiency of the Photodynamic Inactivation of Candida albicans Using CdTe Quantum Dots, Zn(II) Porphyrin and Their Conjugates as Photosensitizers

The application of fluorescent II-VI semiconductor quantum dots (QDs) as active photosensitizers in photodymanic inactivation (PDI) is still being evaluated. In the present study, we prepared 3 nm size CdTe QDs coated with mercaptosuccinic acid and conjugated them electrostatically with Zn(II) meso-tetrakis (N-ethyl-2-pyridinium-2-yl) porphyrin (ZnTE-2-PyP or ZnP), thus producing QDs-ZnP conjugates. We evaluated the capability of the systems, bare QDs and conjugates, to produce reactive oxygen species (ROS) and applied them in photodynamic inactivation in cultures of Candida albicans by irradiating the QDs and testing the hypothesis of a possible combined contribution of the PDI action. Tests of in vitro cytotoxicity and phototoxicity in fibroblasts were also performed in the presence and absence of light irradiation. The overall results showed an efficient ROS production for all tested systems and a low cytotoxicity (cell viability >90%) in the absence of radiation. Fibroblasts incubated with the QDs-ZnP and subjected to irradiation showed a higher cytotoxicity (cell viability <90%) depending on QD concentration compared to the bare groups. The PDI effects of bare CdTe QD on Candida albicans demonstrated a lower reduction of the cell viability (~1 log10) compared to bare ZnP which showed a high microbicidal activity (~3 log10) when photoactivated. The QD-ZnP conjugates also showed reduced photodynamic activity against C. albicans compared to bare ZnP and we suggest that the conjugation with QDs prevents the transmembrane cellular uptake of the ZnP molecules, reducing their photoactivity.

Bioluminescent magnetic nanoparticles as potential imaging agents for mammalian spermatozoa

BACKGROUND

Nanoparticles have emerged as key materials for developing applications in nanomedicine, nanobiotechnology, bioimaging and theranostics. Existing bioimaging technologies include bioluminescent resonance energy transfer-conjugated quantum dots (BRET-QDs). Despite the current use of BRET-QDs for bioimaging, there are strong concerns about QD nanocomposites containing cadmium which exhibits potential cellular toxicity.

RESULTS

In this study, bioluminescent composites comprised of magnetic nanoparticles and firefly luciferase (Photinus pyralis) are examined as potential light-emitting agents for imaging, detection, and tracking mammalian spermatozoa. Characterization was carried out using infrared spectroscopy, TEM and cryo-TEM imaging, and ζ-potential measurements to demonstrate the successful preparation of these nanocomposites. Binding interactions between the synthesized nanoparticles and spermatozoon were characterized using confocal and atomic/magnetic force microscopy. Bioluminescence imaging and UV-visible-NIR microscopy results showed light emission from sperm samples incubated with the firefly luciferase-modified nanoparticles. Therefore, these newly synthesized luciferase-modified magnetic nanoparticles show promise as substitutes for QD labeling, and can potentially also be used for in vivo manipulation and tracking, as well as MRI techniques.

CONCLUSIONS

These preliminary data indicate that luciferase-magnetic nanoparticle composites can potentially be used for spermatozoa detection and imaging. Their magnetic properties add additional functionality to allow for manipulation, sorting, or tracking of cells using magnetic techniques.

10-Fold Quantum Yield Improvement of Ag2S Nanoparticles by Fine Compositional Tuning

Ag₂S semiconductor nanoparticles (NPs) are near-infrared luminescent probes with outstanding properties (good biocompatibility, optimum spectral operation range, and easy biofunctionalization) that make them ideal probes for in vivo imaging. Ag₂S NPs have, indeed, made possible amazing challenges including in vivo brain imaging and advanced diagnosis of the cardiovascular system. Despite the continuous redesign of synthesis routes, the emission quantum yield (QY) of Ag₂S NPs is typically below 0.2%. This leads to a low luminescent brightness that avoids their translation into the clinics. In this work, an innovative synthetic methodology that permits a 10-fold increment in the absolute QY from 0.2 up to 2.3% is presented. Such an increment in the QY is accompanied by an enlargement of photoluminescence lifetimes from 184 to 1200 ns. The optimized synthetic route presented here is based on a fine control over both the Ag core and the Ag/S ratio within the NPs. Such control reduces the density of structural defects and decreases the nonradiative pathways. In addition, we demonstrate that the superior performance of the Ag₂S NPs allows for high-contrast in vivo bioimaging.

Toxicity of Graphene Quantum Dots in Zebrafish Embryo

OBJECTIVE

To evaluate the bio-safety of graphene quantum dots (GQDs), we studied its effects on the embryonic development of zebrafish.

METHODS

In vivo, biodistribution and the developmental toxicity of GQDs were investigated in embryonic zebrafish at exposure concentrations ranging from 12.5-200 μg/mL for 4-96 h post-fertilization (hpf). The mortality, hatch rate, malformation, heart rate, GQDs uptake, spontaneous movement, and larval behavior were examined.

RESULTS

The fluorescence of GQDs was mainly localized in the intestines and heart. As the exposure concentration increased, the hatch and heart rate decreased, accompanied by an increase in mortality. Exposure to a high level of GQDs (200 μg/mL) resulted in various embryonic malformations including pericardial edema, vitelline cyst, bent spine, and bent tail. The spontaneous movement significantly decreased after exposure to GQDs at concentrations of 50, 100, and 200 μg/mL. The larval behavior testing (visible light test) showed that the total swimming distance and speed decreased dose-dependently. Embryos exposed to 12.5 μg/mL showed hyperactivity while exposure to higher concentrations (25, 50, 100, and 200 μg/mL) caused remarkable hypoactivity in the light-dark test.

CONCLUSION

Low concentrations of GQDs were relatively non-toxic. However, GQDs disrupt the progression of embryonic development at concentrations exceeding 50 μg/mL.