Effect of Nanoparticle Surface Coating on Cell Toxicity and Mitochondria Uptake

Recent Breakthroughs in Using Quantum Dots for Cancer Imaging and Drug Delivery Purposes

Cancer is one of the leading causes of death worldwide. Because each person's cancer may be unique, diagnosing and treating cancer is challenging. Advances in nanomedicine have made it possible to detect tumors and quickly investigate tumor cells at a cellular level in contrast to prior diagnostic techniques. Quantum dots (QDs) are functional nanoparticles reported to be useful for diagnosis. QDs are semiconducting tiny nanocrystals, 2-10 nm in diameter, with exceptional and useful optoelectronic properties that can be tailored to sensitively report on their environment. This review highlights these exceptional semiconducting QDs and their properties and synthesis methods when used in cancer diagnostics. The conjugation of reporting or binding molecules to the QD surface is discussed. This review summarizes the most recent advances in using QDs for in vitro imaging, in vivo imaging, and targeted drug delivery platforms in cancer applications.

Synthesis, radiolabeling, and preclinical in vivo evaluation of 68Ga-radiolabelled nanodiamonds

PURPOSE

Nanodiamonds (NDs) represent a new class of nanoparticles and have gained increasing interest in medical applications. Modifying the surface coating by attaching binding ligands or imaging probes can transform NDs into multi-modal targeting probes. This study evaluated the biokinetics and biodistribution of ⁶⁸Ga-radiolabelled NDs in a xenograft model.

PROCEDURES

NDs were coated with an albumin-derived copolymer modified with desferrioxamine to provide a chelator for radiolabeling. In vivo studies were conducted in AR42J tumor-bearing CD1 mice to evaluate biodistribution and tumor accumulation of the NDs.

RESULTS

Coated NDs were successfully radiolabeled using ⁶⁸Ga at room temperature with radiolabeling efficiencies up to 91.8 ± 3.2 % as assessed by radio-TLC. In vivo studies revealed the highest accumulation in the liver and spleen, whereas tumor radioactivity concentration was low.

CONCLUSIONS

Radiolabeling of coated NDs could be achieved. However, the obtained results indicate these coated NDs' limitations in their biodistribution within the conducted studies.

SiO2 Fibers of Two Lengths and Their Effect on Cellular Responses of Macrophage-like Cells

The immunoreactivity or/and stress response can be induced by nanomaterials’ different properties, such as size, shape, etc. These effects are, however, not yet fully understood. This study aimed to clarify the effects of SiO₂ nanofibers (SiO₂NFs) on the cellular responses of THP-1-derived macrophage-like cells. The effects of SiO₂NFs with different lengths on reactive oxygen species (ROS) and pro-inflammatory cytokines TNF-α and IL-1β in THP-1 cells were evaluated. From the two tested lengths, it was only the L-SiO₂NFs with a length ≈ 44 ± 22 µm that could induce ROS. Compared to this, only S-SiO₂NFs with a length ≈ 14 ± 17 µm could enhance TNF-α and IL-1β expression. Our results suggested that L-SiO₂NFs disassembled by THP-1 cells produced ROS and that the inflammatory reaction was induced by the uptake of S-SiO₂NFs by THP-1 cells. The F-actin staining results indicated that SiO₂NFs induced cell motility and phagocytosis. There was no difference in cytotoxicity between L- and S-SiO₂NFs. However, our results suggested that the lengths of SiO₂NFs induced different cellular responses.

One-Step Aqueous Synthesis of Anionic and Cationic AgInS2 Quantum Dots and Their Utility in Improving the Efficacy of ALA-Based Photodynamic Therapy

Silver–indium–sulfide quantum dots (AIS QDs) have potential applications in many areas, including biomedicine. Their lack of regulated heavy metals, unlike many commercialized QDs, stands out as an advantage, but the necessity for alloyed or core–shell structures and related costly and sophisticated processes for the production of stable and high quantum yield aqueous AIS QDs are the current challenges. The present study demonstrates the one-step aqueous synthesis of simple AgInS₂ QD compositions utilizing for the first time either a polyethyleneimine/2-mercaptopropionic acid (AIS-PEI/2MPA) mixture or only 2-mercaptopropionic acid (AIS-2MPA) as the stabilizing molecules, providing a AgInS₂ portfolio consisting of cationic and anionic AIS QDs, respectively, and tuneable emission. Small AIS QDs with long-term stability and high quantum yields (19–23%) were achieved at a molar ratio of Ag/In/S 1/10/10 in water without any dopant or a semiconductor shell. The theranostic potential of these cationic and anionic AIS QDs was also evaluated in vitro. Non-toxic doses were determined, and fluorescence imaging potential was demonstrated. More importantly, these QDs were electrostatically loaded with zwitterionic 5-aminolevulinic acid (ALA) as a prodrug to enhance the tumor availability of ALA and to improve ALA-induced porphyrin photodynamic therapy (PDT). This is the first study investigating the influence of nanoparticle charge on ALA binding, release, and therapeutic efficacy. Surface charge was found to be more critical in cellular internalization and dark toxicity rather than drug loading and release. Both QDs provided enhanced ALA release at acidic pH but protected the prodrug at physiological pH, which is critical for tumor delivery of ALA, which suffers from low bioavailability. The PDT efficacy of the ALA-loaded AIS QDs was tested in 2D monolayers and 3D constructs of HT29 and SW480 human colon adenocarcinoma cancer cell lines. The incorporation of ALA delivery by the AIS QDs, which on their own do not cause phototoxicity, elicited significant cell death due to enhanced light-induced ROS generation and apoptotic/necrotic cell death, reducing the IC50 for ALA dramatically to about 0.1 and 0.01 mM in anionic and cationic AIS QDs, respectively. Combined with simple synthetic methods, the strong intracellular photoluminescence of AIS QDs, good biocompatibility of especially the anionic AIS QDs, and the ability to act as drug carriers for effective PDT signify that the AIS QDs, in particular AIS-2MPA, are highly promising theranostic QDs.

Use of the ALA-loaded cationic and anionic AIS QDs for visible light PDT coupled with QD-based optical imaging in the medical imaging window was studied.

Fate of CdSe/ZnS quantum dots in cells: Endocytosis, translocation and exocytosis

Semiconductor quantum dots (QDs) have been extensively explored for extensive bioapplications, yet their cellular fate, especially exocytosis, has not been thoroughly investigated. Herein, we systematically investigated the whole cellular process from the endocytosis, intercellular trafficking, to the exocytosis of a typical QD, core/shell CdSe/ZnS QD. Using confocal laser scanning microscopy and flow cytometry, and after carefully eliminating the effect of cell division, we found that the QDs were internalized by HeLa cells with a time-, dose-, and serum-dependent manner. The cellular uptake was inhibited by serum, but eventually peaked after 4-6 h incubation with or without serum. The primary endocytosis pathway was clathrin-mediated, and actin- and microtubule-dependent in the medium with serum, while the caveolae-mediated endocytosis and macropinocytosis were more important for the QDs in the serum-free medium. Inside cells, most QDs distributed in lysosomes, and some entered mitochondria, endoplasmic reticulum, and Golgi apparatus. The translocation of the QDs from other organelles to Golgi apparatus was observed. The exocytosis of QDs was faster than the endocytosis, reaching the maximum in about one hour after cultured in fresh culture medium, with around 60% of the internalized QDs remained undischarged. The exocytosis process was energy- and actin-dependent, and the lysosome exocytosis and endoplasmic reticulum/Golgi pathway were the main routes. This study provides a full picture of behavior and fate of QDs in cells, which may facilitate the design of ideal QDs applied in biomedical and other fields.

Nanoparticles with Multiple Enzymatic Activities Purified from Groundwater Efficiently Cross the Blood-Brain Barrier, Improve Memory, and Provide Neuroprotection

Many engineered nanomaterials (ENMs) and drugs have been fabricated to improve memory and promote neuroprotection, but their use remains challenging due to their high cost, poor ability to penetrate the blood-brain barrier (BBB), and many side effects. Herein, we found that nanoparticles with multiple enzymatic activities purified from groundwater (NMEGs) can efficiently cross the BBB and present memory-enhancing and neuroprotective effects in vitro and in vivo. In contrast to the adverse effects of chemicals and ENMs, NMEGs are able to cross the BBB by endocytosis without damaging the BBB and even possibly promote BBB integrity. NMEGs-treated normal mice were smarter and better behaved than saline-treated normal mice in the open-field test and Morris water maze test. NMEGs can enhance synaptic transmission by increasing neurotransmitter production and activating nicotinic acetylcholine receptors (nAChRs), activate the antioxidant enzyme system, and increase the number of mitochondria and ribosomes in cells. Intravenous NMEGs injection also rescued memory deficits and increased antioxidant capacity in Parkinson's disease (PD) mice due to the antioxidant activity caused by the presence of conjugated double bonds and abundant phenolic -OH groups. This study is a proof-of-principle demonstration that natural products are less expensive, more easily available, safer, and more effective ways to improve memory and promote neuroprotection than ENMs and reported drugs. Our article also shows the potential of NMEGs as a PD treatment in patients via intravenous injection, as they avoid the complex modifications of ENMs. In the future, it will be possible to treat PD by intravenously injecting NMEGs in patients.

Quantum dots as a theranostic approach in Alzheimer's disease: a systematic review

Aim: Quantum dots (QDs) are nanoparticles that have an emerging application as theranostic agents in several neurodegenerative diseases. The advantage of QDs as nanomedicine is due to their unique optical properties that provide high sensitivity, stability and selectivity at a nanoscale range. Objective: To offer renewed insight into current QD research and elucidate its promising application in Alzheimer's disease (AD) diagnosis and therapy. Methods: A comprehensive literature search was conducted in PubMed and Google Scholar databases that included the following search terms: 'quantum dots', 'blood-brain barrier', 'cytotoxicity', 'toxicity' and 'Alzheimer's disease'; PRISMA guidelines were adhered to. Results: Thirty-four publications were selected to evaluate the ability of QDs to cross the blood-brain barrier, potential toxicity and current AD diagnostic and therapeutic applications. Conclusion: QD's unique optical properties and versatility to conjugate to various biomolecules, while maintaining a nanoscale size, render them a promising theranostic tool in AD.

Novel insights into biodegradation, interaction, internalization and impacts of high-aspect-ratio TiO2 nanomaterials: A systematic in vivo study using Drosophila melanogaster

The elongated nature of the high-aspect-ratio nanomaterials (NMs) can help us to obtain valuable information on its biodegradation, physical interaction with target-cells, and internalization. Three different length nano-titanium have been studied using Drosophila, TEM, and different biological markers. Nano-titanium, regardless of its shape, was eroded and degraded just entering the gut lumen of the larvae. Results showed that the distinguished shape of nanowires helps to understand the interactions of NMs with the intestinal barrier. The peritrophic membrane, as the first defense line of the intestinal barrier, succeeded in the reservation of NMs, though the perpendicular particles of nanowires stabbing it, making pores, and permitting their translocation into intestinal cells. On the other side, the exposure to TiO₂NPs did not decrease egg-to-adult viability, but all its different shapes, especially nanowires, mediated a wide molecular response including changes of expression in genes involved in stress, antioxidant, repair, and physical interaction responses. All these changes concerning their ability to elevate ROS levels ultimately led to potential genotoxicity. So, the high aspect ratio NMs are efficient in understanding the outstanding issues of NMs exposure, but at the same time could induce genotoxic impact rather than the low aspect ones.

The cytotoxicity of core-shell or non-shell structure quantum dots and reflection on environmental friendly: A review

Quantum dots are widely applicated into bioindustry and research owing to its superior properties such as broad excitation spectra, narrow bandwidth emission spectra and high resistance to photo-bleaching. However, the toxicity of quantum dots should not be underestimated and aroused widespread concern. The surface properties and size of quantum dots are critical relevant properties on toxicity. Then, the core/shell structure becomes one common way to affect the activity of quantum dots such as enhance biocompatibility and stability. Except those toxicity it induced, the problem it brought into the environment such as the degradation of quantum dot similarly becomes a hot issue. This review initially took a brief scan of current research on the cytotoxicity of QDs and the mechanism behind that over the past five years. Mainly discussion concentrated on the diversity of structure on quantum dots whether played a key role on the cytotoxicty of quantum dots. It also discussed the role of different shells with metal or nonmetal cores and the influence on the environment.

Disturbed mitochondrial quality control involved in hepatocytotoxicity induced by silica nanoparticles

The extensive application of silica nanoparticles (SiNPs) brings about inevitable occupational, environmental, and even iatrogenic exposure for human beings. The liver, which is rich in mitochondria, is one of the target organs of SiNPs, but the underlying mechanisms by which these nanoparticles (NPs) interact with liver mitochondria and affect their functions still remain unclear. In the present study, we examined silicon nanoparticle (SiNP)-induced mitochondrial dysfunction, and further revealed its negative effects on mitochondrial quality control (MQC) in the human liver cell line L-02, including mitochondrial dynamics, mitophagy and biogenesis. Consequently, SiNPs induced cellular injury, accompanied by mitochondrial dysfunction, including mitochondrial reactive oxygen generation and mitochondrial membrane potential collapse. In line with the transmission electron microscopy (TEM)-observed abnormalities in the mitochondrial morphology and length distribution, a fission phenotype was manifested in the mitochondria of SiNP-exposed cells, and up-regulated DRP1 and FIS1, and down-regulated MFN1, were detected. Furthermore, the enhanced LC3II level, colocalization of the mitochondria and lysosomes, activated PINK1/Parkin signaling, and accumulated p62 in the SiNP-exposed cells suggested mitophagy disorder triggered by SiNPs. In addition, SiNPs inhibited mito-biogenesis, as evidenced by the reduced mitochondrial mass and mtDNA copy number, as well as the suppressed PGC1α-NRF1-TFAM signaling pathway. Overall, the study demonstrates that SiNPs trigger hepatocytotoxicity through interfering with the MQC process, bringing in excessive mitochondrial fission, mitophagy disorder and suppressed mito-biogenesis, leading to mitochondrial dysfunction and ensuing cell damage, and ultimately contributing to the occurrence and development of liver diseases. Our research could provide important experimental evidence related to safety assessments of SiNPs, especially in the field of biomedical applications.

Cationic Liposome/DNA Complexes Mediate Antitumor Immunotherapy by Promoting Immunogenic Tumor Cell Death and Dendritic Cell Activation

Immunotherapy has been successfully used in the treatment of multiple malignancies, but clinical studies revealed low response rates. Thus, the development of new effective immunotherapeutic modalities is urgently needed. Successfully inducing tumor cell death with enhanced antigenicity is important for the expansion and differentiation of tumor-specific CD8⁺ cytotoxic T lymphocytes. Cationic liposome/DNA complexes (CLN/DNA), which usually have obvious cytotoxic effects, may improve the antitumor immunity through enhancing the immunogenicity of dying tumor cells. Herein, we report that a plasmid DNA-encapsulated cationic lipid nanoparticle formulated with cholesterol, DOTAP, and DSPE-mPEG₂₀₀₀ significantly increases the tumor cell death with high antigenicity in vitro. Furthermore, the cationic liposome/DNA complex (CLN/DNA) treatment promotes the activation of dendritic cells (DCs). We also find that the intratumorally injected CLN/DNA successfully promoted the activation of DCs in the tumor-draining lymph node. Importantly, both local tumor growth and distant tumor formation were significantly inhibited by T cell-dependent antitumor immune responses after intratumoral injection of CLN/DNA. This study presents a simple and effective strategy for improving the cancer immunotherapy.

In vivo Comparison of the Biodistribution and Toxicity of InP/ZnS Quantum Dots with Different Surface Modifications

INTRODUCTION

Indium phosphide (InP) quantum dots (QDs) have shown a broad application prospect in the fields of biophotonics and nanomedicine. However, the potential toxicity of InP QDs has not been systematically evaluated. In particular, the effects of different surface modifications on the biodistribution and toxicity of InP QDs are still unknown, which hinders their further developments. The present study aims to investigate the biodistribution and in vivo toxicity of InP/ZnS QDs.

METHODS

Three kinds of InP/ZnS QDs with different surface modifications, hQDs (QDs-OH), aQDs (QDs-NH2), and cQDs (QDs-COOH) were intravenously injected into BALB/c mice at the dosage of 2.5 mg/kg BW or 25 mg/kg BW, respectively. Biodistribution of three QDs was determined through cryosection fluorescence microscopy and ICP-MS analysis. The subsequent effects of InP/ZnS QDs on histopathology, hematology and blood biochemistry were evaluated at 1, 3, 7, 14 and 28 days post-injection.

RESULTS

These types of InP/ZnS QDs were rapidly distributed in the major organs of mice, mainly in the liver and spleen, and lasted for 28 days. No abnormal behavior, weight change or organ index were observed during the whole observation period, except that 2 mice died on Day 1 after 25 mg/kg BW hQDs treatment. The results of H&E staining showed that no obvious histopathological abnormalities were observed in the main organs (including heart, liver, spleen, lung, kidney, and brain) of all mice injected with different surface-functionalized QDs. Low concentration exposure of three QDs hardly caused obvious toxicity, while high concentration exposure of the three QDs could cause some changes in hematological parameters or biochemical parameters related to liver function or cardiac function. More attention needs to be paid on cQDs as high-dose exposure of cQDs induced death, acute inflammatory reaction and slight changes in liver function in mice.

CONCLUSION

The surface modification and exposure dose can influence the biological behavior and in vivo toxicity of QDs. The surface chemistry should be fully considered in the design of InP-based QDs for their biomedical applications.

Insights into Theranostic Properties of Titanium Dioxide for Nanomedicine

Titanium dioxide (TiO2) nanostructures exhibit a broad range of theranostic properties that make them attractive for biomedical applications. TiO2 nanostructures promise to improve current theranostic strategies by leveraging the enhanced quantum confinement, thermal conversion, specific surface area, and surface activity. This review highlights certain important aspects of fabrication strategies, which are employed to generate multifunctional TiO2 nanostructures, while outlining post-fabrication techniques with an emphasis on their suitability for nanomedicine. The biodistribution, toxicity, biocompatibility, cellular adhesion, and endocytosis of these nanostructures, when exposed to biological microenvironments, are examined in regard to their geometry, size, and surface chemistry. The final section focuses on recent biomedical applications of TiO2 nanostructures, specifically evaluating therapeutic delivery, photodynamic and sonodynamic therapy, bioimaging, biosensing, tissue regeneration, as well as chronic wound healing.

Liposomal delivery of CRISPR/Cas9

Liposomes are one of the most widely investigated carriers for CRISPR/Cas9 delivery. The surface properties of liposomal carriers, including the surface charge, PEGylation, and ligand modification can significantly affect the gene silencing efficiency. Three barriers of systemic CRISPR/Cas9 delivery (long blood circulation, efficient tumor penetration, and efficient cellular uptake/endosomal escape) are analyzed on liposomal carriers with different surface charges, PEGylations, and ligand modifications. Cationic formulations dominate CRISPR/Cas9 delivery and neutral formulations also have good performance while anionic formulations are generally not proper for CRISPR/Cas9 delivery. The PEG dilemma (prolonged blood circulation vs. reduced cellular uptake/endosomal escape) and the side effect of repeated PEGylated formulation (accelerated blood clearance) were discussed. Effects of ligand modification on cationic and neutral formulations were analyzed. Finally, we summarized the achievements in liposomal CRISPR/Cas9 delivery, outlined existing problems, and provided some future perspectives. Liposomes are one of the most widely investigated carriers for CRISPR/Cas9 delivery. The surface properties of liposomal carriers, including the surface charge, PEGylation, and ligand modification can significantly affect the gene silencing efficiency. Three barriers of systemic siRNA delivery (long blood circulation, efficient tumor penetration, and efficient cellular uptake/endosomal escape) are analyzed on liposomal carriers with different surface charges, PEGylations, and ligand modifications. Cationic formulations dominate CRISPR/Cas9 delivery and neutral formulations also have good performance while anionic formulations are generally not proper for CRISPR/Cas9 delivery. The PEG dilemma (prolonged blood circulation vs. reduced cellular uptake/endosomal escape) and the side effect of repeated PEGylated formulation (accelerated blood clearance) were discussed. Effects of ligand modification on cationic and neutral formulations were analyzed. Finally, we summarized the achievements in liposomal CRISPR/Cas9 delivery, outlined existing problems, and provided some future perspectives.

Cardiotoxicity of Intravenously Administered CdSe/ZnS Quantum Dots in BALB/c Mice

Since CdSe quantum dots (QDs) are increasingly used in electronics, medical, and pharmaceutical science due to their excellent optical properties, it is necessary to carry out thorough and systematic studies on their biosafety. Numerous studies have reported the toxicity of QDs on liver, kidney, immune system, and reproductive system. However, few studies have been done on the cardiotoxicity of QDs. In this study, we administered carboxylated CdSe/ZnS QDs in BALB/c mice via the tail vein and analyzed the in vivo cardiotoxicity of CdSe/ZnS QDs. The body weight, hematology, serum biochemistry, histology, heart elements concentration, echocardiography, and heart oxidative stress markers were carried out at different time. There were no significant differences in body weight and heart organ index between QDs group and the control group. Hematology results showed the platelet (PLT) counts on Day 1 and Day 42 in both high dose QDs group and low dose QDs group, and the PLT counts on Day1 in the high dose group were significantly higher than that in control group. Serum biochemistry results showed that lactate dehydrogenase (LDH), creatine kinase (CK), and creatine kinase isoenzyme (CK-MB) of mice exposed to CdSe/ZnS QDs were significantly higher than that of the control group on Day 1, and CK-MB levels still remained high on Day 7. A higher concentration of Cd was observed in the heart of CdSe/ZnS QDs exposed mice on Day 42, whereas no Cd was detected in the control group, which suggested that QDs can accumulate in heart. No significant histopathological changes and cardiac function were observed in all mice at different time after treatment. Increased level of glutathione peroxidase (GPx) and malondialdehyde (MDA) was observed in mice administered with high dose QDs on Day 1, and increased level of total antioxidant capacity (T-AOC) and MDA activities was observed on Day 42. These results indicated that CdSe/ZnS QDs could accumulate in heart, cause some biochemical indicators change, induce oxidative damage, and have cardiotoxicity. Our findings might provide valuable information on the biological safety evaluation of the cardiovascular system of QDs.

Pancreatic islet surface engineering with a starPEG-chondroitin sulfate nanocoating

Islet transplantation is one of the most promising therapeutic options that could restore euglycaemia in type 1 diabetic individuals.

Adenovirus-Mediated CRM197 Sensitizes Human Glioma Cells to Gemcitabine by the Mitochondrial Pathway

PURPOSE

The cross-reacting material 197 (CRM197) is a mutation of the diphtheria toxin. The protein of CRM197 was used successfully for the therapy of various tumors in the recent studies. In this study, the recombinant adenoviruses containing the CRM197gene(AdCRM197) were used to enhance the cellar toxicity of gemcitabine in human glioma U87, U251, and H4 cells.

PROCEDURES

MTT assay and flow cytometric analysis were performed to test the apoptosis of the U87, U251 and H4 cells with the combined treatment of AdCRM197 plus gemcitabine. Western blotting analyses were carried out to detect the cell apoptosis of the mitochondrial pathway. And the xenograft nude mice were used to observe the enhanced antitumor effect of AdCRM197 in vivo.

RESULTS

AdCRM197 sensitizes human glioma cells to gemcitabine in vitro by the mitochondrial pathway. Tumor volume was inhibited and survival time was prolonged in the U251 or U87 xenografted nude mice with gemcitabine plus AdCRM197. The enhanced antitumor effect of AdCRM197 was also detected by the immunohistochemical analyses and TUNEL staining.

CONCLUSION

The authors found that AdCRM197 sensitized the human glioma to gemcitabine not only in vitro but also in vivo. They provide the first evidence that adenovirus-mediated CRM197 may be a potential chemosensitizing agent for the treatment of cancer. The diphtheria toxin is of great toxicity that even one molecule of diphtheria toxin is enough to kill one cell. However, because of the high toxicity, the diphtheria toxin would kill the packing cells when it is being packaged into the recombinant viruses. Therefore, the diphtheria toxin is hard to be used in the gene therapy for virus vectors. The cross-reacting material 197 (CRM197) is a mutation of the diphtheria toxin. Unlike DTA, CRM197 exhibit a weak toxicity. The week toxicity of CRM197 is a good feature for the virus packaging. In the present study, we used a recombinant adenovirus which carried a CRM197 gene (AdCRM197) to enhance the cellar toxicity of gemcitabine in human glioma cells.

Recent Advances in Mitochondria-Targeted Gene Delivery

Mitochondria are the energy-producing organelles of cells. Mitochondrial dysfunctions link to various syndromes and diseases including myoclonic epilepsy and ragged-red fiber disease (MERRF), Leigh syndrome (LS), and Leber hereditary optic neuropathy (LHON). Primary mitochondrial diseases often result from mutations of mitochondrial genomes and nuclear genes that encode the mitochondrial components. However, complete intracellular correction of the mutated genetic parts relevant to mitochondrial structures and functions is technically challenging. Instead, there have been diverse attempts to provide corrected genetic materials with cells. In this review, we discuss recent novel physical, chemical and biological strategies, and methods to introduce genetic cargos into mitochondria of eukaryotic cells. Effective mitochondria-targeting gene delivery systems can reverse multiple mitochondrial disorders by enabling cells to produce functional mitochondrial components.

Cytotoxicity of InP/ZnS Quantum Dots With Different Surface Functional Groups Toward Two Lung-Derived Cell Lines

Although InP/ZnS quantum dots (QDs) have emerged as a presumably less hazardous alternative to cadmium-based QDs, their toxicity has not been fully understood. In this work, we report the cytotoxicity of InP/ZnS QDs with different surface groups (NH₂, COOH, OH) toward two lung-derived cell lines. The diameter and the spectra of InP/ZnS QDs were characterized and the hydrodynamic size of QDs in aqueous solution was compared. The confocal laser scanning microscopy was applied to visualize the labeling of QDs for human lung cancer cell HCC-15 and Alveolar type II epithelial cell RLE-6TN. The flow cytometry was used to confirm qualitatively the uptake efficiency of QDs, the cell apoptosis and ROS generation, respectively. The results showed that in deionized water, InP/ZnS-OH QDs were easier to aggregate, and the hydrodynamic size was much greater than the other InP/ZnS QDs. All these InP/ZnS QDs were able to enter the cells, with higher uptake efficiency for InP/ZnS-COOH and InP/ZnS-NH₂ at low concentration. High doses of InP/ZnS QDs caused the cell viability to decrease, and InP/ZnS-COOH QDs and InP/ZnS-NH₂ QDs appeared to be more toxic than InP/ZnS-OH QDs. In addition, all these InP/ZnS QDs promoted cell apoptosis and intracellular ROS generation after co-cultured with cells. These results suggested that appropriate concentration and surface functional groups should be optimized when InP/ZnS QDs are utilized for biological imaging and therapeutic purpose in the future.