Transferrin-conjugated magnetic silica PLGA nanoparticles loaded with doxorubicin and paclitaxel for brain glioma treatment

The effective treatment of malignant brain glioma is hindered by the poor transport across the blood–brain barrier (BBB) and the low penetration across the blood-tumor barrier (BTB). In this study, transferrin-conjugated magnetic silica PLGA nanoparticles (MNP-MSN-PLGA-Tf NPs) were formulated to overcome these barriers. These NPs were loaded with doxorubicin (DOX) and paclitaxel (PTX), and their anti-proliferative effect was evaluated in vitro and in vivo. The in vitro cytotoxicity of drug-loaded NPs was evaluated in U-87 cells. The delivery and the subsequent cellular uptake of drug-loaded NPs could be enhanced by the presence of magnetic field and the usage of Tf as targeting ligand, respectively. In particular, cells treated with DOX-PTX-NPs-Tf with magnetic field showed the highest cytotoxicity as compared to those treated with DOX-PTX-NPs-Tf, DOX-PTX-NPs, DOX-PTX-NPs-Tf with free Tf. The in vivo therapeutic efficacy of drug-loaded NPs was evaluated in intracranial U-87 MG-luc2 xenograft of BALB/c nude mice. In particular, the DOX-PTX-NPs-Tf treatment exhibited the strongest anti-glioma activity as compared to the PTX-NPs-Tf, DOX-NPs-Tf or DOX-PTX-NPs treatment. Mice did not show acute toxicity after administrating with blank MNP-MSN-PLGA-Tf NPs. Overall, MNP-MSN-PLGA-Tf NPs are promising carriers for the delivery of dual drugs for effective treatment of brain glioma.     

Vascular toxicity of ultra-small TiO2 nanoparticles and single walled carbon nanotubes in vitro and in vivo

Ultra-small nanoparticles (USNPs) at 1–3 nm are a subset of nanoparticles (NPs) that exhibit intermediate physicochemical properties between molecular dispersions and larger NPs. Despite interest in their utilization in applications such as theranostics, limited data about their toxicity exist. Here the effect of TiO₂-USNPs on endothelial cells in vitro, and zebrafish embryos in vivo, was studied and compared to larger TiO₂-NPs (30 nm) and to single walled carbon nanotubes (SWCNTs). In vitro exposure showed that TiO₂-USNPs were neither cytotoxic, nor had oxidative ability, nevertheless were genotoxic. In vivo experiment in early developing zebrafish embryos in water at high concentrations of TiO₂-USNPs caused mortality possibly by acidifying the water and caused malformations in the form of pericardial edema when injected. Myo1C involved in glomerular development of zebrafish embryos was upregulated in embryos exposed to TiO₂-USNPs. They also exhibited anti-angiogenic effects both in vitro and in vivo plus decreased nitric oxide concentration. The larger TiO₂-NPs were genotoxic but not cytotoxic. SWCNTs were cytotoxic in vitro and had the highest oxidative ability. Neither of these NPs had significant effects in vivo. To our knowledge this is the first study evaluating the effects of TiO₂-USNPs on vascular toxicity in vitro and in vivo and this strategy could unravel USNPs potential applications.     

Effects of mannose density on in vitro and in vivo cellular uptake and RNAi efficiency of polymeric nanoparticles

To evaluate the effects of mannose density on in vitro and in vivo cellular uptake and RNA interference (RNAi) efficiency of polymeric nanoparticles (NPs) in macrophages, mannose-modified trimethyl chitosan-cysteine (MTC) conjugates with mannose densities of 4%, 13%, and 21% (MTC-4, MTC-13, and MTC-21) were synthesized. Tumor necrosis factor-alpha (TNF-α) siRNA loaded MTC NPs with particle sizes of ∼150 nm exhibited desired structural stability and effectively protected siRNA from enzymatic degradation. Generally, cellular uptake and RNAi efficiency were affected by mannose density. As expected, MTC-21 NPs presented the maximum in vitro uptake and RNAi efficacy in Raw 264.7 cells among all NPs tested. However, MTC-4 NPs exhibited the optimal in vivo uptake by peritoneal exudate cell macrophages (PECs). In the inflammation model of acute hepatic injury, orally delivered MTC-4 and MTC-13 NPs worked better in silencing TNF-α expression and alleviating liver damage than MTC-21 NPs. As for the ulcerative colitis model, MTC-4 NPs outperformed MTC-13 and MTC-21 NPs with respect to TNF-α knockdown and therapeutic efficacy following oral administration. These results highlighted the importance of ligand density in cellular uptake and RNAi efficiency, which could serve as a guideline in the rational design of targeted nanocarriers for anti-inflammation therapy.     

Hyaluronic acid-modified hydrothermally synthesized iron oxide nanoparticles for targeted tumor MR imaging

We report a polyethyleneimine (PEI)-mediated approach to synthesizing hyaluronic acid (HA)-targeted magnetic iron oxide nanoparticles (Fe₃O₄ NPs) for in vivo targeted tumor magnetic resonance (MR) imaging applications. In this work, Fe₃O₄ NPs stabilized by PEI were first synthesized via a one-pot hydrothermal method. The formed PEI-stabilized Fe₃O₄ NPs were then modified with fluorescein isothiocyanate (FI) and HA with two different molecular weights to obtain two different Fe₃O₄ NPs (Fe₃O₄–PEI–FI–HA_6K and Fe₃O₄–PEI–FI–HA_31K NPs) with a size of 15–16 nm. The formed HA-modified multifunctional Fe₃O₄ NPs were characterized via different techniques. We show that the multifunctional Fe₃O₄ NPs are water-dispersible and colloidal stable in different aqueous media. In vitro cell viability and hemolysis studies reveal that the particles are quite cytocompatible and hemocompatible in the given concentration range. Furthermore, confocal microscopy and flow cytometry data demonstrate that HA-targeted Fe₃O₄ NPs are able to be uptaken specifically by cancer cells overexpressing CD44 receptors, and be used as efficient probes for targeted MR imaging of cancer cells in vitro and xenografted tumor models in vivo. With the tunable amine-based conjugation chemistry, the PEI-stabilized Fe₃O₄ NPs may be functionalized with other biological ligands or drugs for diagnosis and therapy of different biological systems.     

The effect of hyperbranched polyglycerol coatings on drug delivery using degradable polymer nanoparticles

A key attribute for nanoparticles (NPs) that are used in medicine is the ability to avoid rapid uptake by phagocytic cells in the liver and other tissues. Poly(ethylene glycol) (PEG) coatings has been the gold standard in this regard for several decades. Here, we examined hyperbranched polyglycerols (HPG) as an alternate coating on NPs. In earlier work, HPG was modified with amines and subsequently conjugated to poly(lactic acid) (PLA), but that approach compromised the ability of HPG to resist non-specific adsorption of biomolecules. Instead, we synthesized a copolymer of PLA–HPG by a one-step esterification. NPs were produced from a single emulsion using PLA–HPG: fluorescent dye or the anti-tumor agent camptothecin (CPT) were encapsulated at high efficiency in the NPs. PLA–HPG NPs were quantitatively compared to PLA–PEG NPs, produced using approaches that have been extensively optimized for drug delivery in humans. Despite being similar in size, drug release profile and in vitro cytotoxicity, the PLA–HPG NPs showed significantly longer blood circulation and significantly less liver accumulation than PLA–PEG. CPT-loaded PLA–HPG NPs showed higher stability in suspension and better therapeutic effectiveness against tumors in vivo than CPT-loaded PLA–PEG NPs. Our results suggest that HPG is superior to PEG as a surface coating for NPs in drug delivery.     

PEGylated PAMAM dendrimer–doxorubicin conjugate-hybridized gold nanorod for combined photothermal-chemotherapy

We prepared pH-sensitive drug–dendrimer conjugate-hybridized gold nanorod as a promising platform for combined cancer photothermal-chemotherapy under in vitro and in vivo conditions. Poly(ethylene glycol)-attached PAMAM G4 dendrimers (PEG–PAMAM) were first covalently linked on the surface of mercaptohexadecanoic acid-functionalized gold nanorod (MHA-AuNR), with subsequent conjugation of anti-cancer drug doxorubicin (DOX) to dendrimer layer using an acid-labile-hydrazone linkage to afford PEG–DOX–PAMAM–AuNR particles. The particles with a high PEG–PAMAM dendrimer coverage density (0.28 per nm² AuNR) showed uniform sizes and excellent colloidal stability. In vitro drug release studies demonstrated that DOX released from PEG–DOX–PAMAM–AuNR was negligible under normal physiological pH, but it was enhanced significantly at a weak acidic pH value. The efficient intracellular acid-triggered DOX release inside of lysosomes was confirmed using confocal laser scanning microscopy analysis. Furthermore, the combined photothermal-chemo treatment of cancer cells using PEG–DOX–PAMAM–AuNR for synergistic hyperthermia ablation and chemotherapy was demonstrated both in vitro and in vivo to exhibit higher therapeutic efficacy than either single treatment alone, underscoring the great potential of PEG–DOX–PAMAM–AuNR particles for cancer therapy.     

Intra-articular delivery of kartogenin-conjugated chitosan nano/microparticles for cartilage regeneration

We developed an intra-articular (IA) drug delivery system to treat osteoarthritis (OA) that consisted of kartogenin conjugated chitosan (CHI-KGN). Kartogenin, which promotes the selective differentiation of mesenchymal stem cells (MSCs) into chondrocytes, was conjugated with low-molecular-weight chitosan (LMWCS) and medium-molecular-weight chitosan (MMWCS) by covalent coupling of kartogenin to each chitosan using an ethyl(dimethylaminopropyl) carbodiimide (EDC)/N-hydroxysuccinimide (NHS) catalyst. Nanoparticles (NPs, 150 ± 39 nm) or microparticles (MPs, 1.8 ± 0.54 μm) were fabricated from kartogenin conjugated-LMWCS and –MMWCS, respectively, by an ionic gelation using tripolyphosphate (TPP). The in vitro release profiles of kartogenin from the particles showed sustained release for 7 weeks. When the effects of the CHI-KGN NPs or CHI-KGN MPs were evaluated on the in vitro chondrogenic differentiation of human bone marrow MSCs (hBMMSCs), the CHI-KGN NPs and CHI-KGN MPs induced higher expression of chondrogenic markers from cultured hBMMSCs than unconjugated kartogenin. In particular, hBMMSCs treated with CHI-KGN NPs exhibited more distinct chondrogenic properties in the long-term pellet cultures than those treated with CHI-KGN MPs. The in vivo therapeutic effects of CHI-KGN NPs or CHI-KGN MPs were investigated using a surgically-induced OA model in rats. The CHI-KGN MPs showed longer retention time in the knee joint than the CHI-KGN NPs after IA injection in OA rats. The rats treated with CHI-KGN NPs or CHI-KGN MPs by IA injection showed much less degenerative changes than untreated control or rats treated with unconjugated kartogenin. In conclusion, CHI-KGN NPs or CHI-KGN MPs can be useful polymer-drug conjugates as an IA drug delivery system to treat OA.     

Core-Shell type lipid/rPAA-Chol polymer hybrid nanoparticles for in vivo siRNA delivery

Our previous study had reported that cholesterol-grafted poly(amidoamine) (rPAA-Chol polymer) was able to self-assemble into cationic nanoparticles and act as a potential carrier for siRNA transfection. In this study, the core–shell type lipid/rPAA-Chol hybrid nanoparticles (PEG-LP/siRNA NPs and T7-LP/siRNA NPs) were developed for improving in vivo siRNA delivery by modifying the surface of rPAA-Chol/siRNA nanoplex core with a lipid shell, followed by post-insertion of polyethylene glycol phospholipid (DSPE-PEG) and/or peptide (HAIYPRH, named as T7) modified DSPE-PEG-T7. The integrative hybrid nanostructures of LP/siRNA NPs were evidenced by dynamic light scattering (DLS), confocal laser scanning microscope (CLSM), cryo-transmission electron microscope (Cryo-TEM) and surface plasmon resonance (SPR) assay. It was demonstrated that the T7 peptide modified LP/siRNA NPs (T7-LP/siRNA NPs) exhibited uniform and spherical structures with particle size of 99.39 ± 0.65 nm and surface potential of 42.53 ± 1.03 mV, and showed high cellular uptake efficiency and rapid endosomal/lysosomal escape ability in MCF-7 cells. Importantly, in vitro gene silencing experiment demonstrated that both of pegylated and targeted LP/siEGFR NPs exhibited significantly stronger downregulation of EGFR protein expression level in MCF-7 cells, compared to that of the physical mixture of siRNA lipoplexes and rPAA-Chol/siRNA nanoplexes. In vivo tumor therapy on nude mice bearing MCF-7 tumors further confirmed that the targeted T7-LP/siEGFR NPs exhibited the greatest inhibition on tumor growth via transferrin receptor-mediated targeting delivery, without any activation of immune responses and significant body weight loss following systemic administration. These findings indicated that the core-shell type T7-LP/siRNA nanoparticles would be promising siRNA delivery systems for in vivo tumor-targeted therapy.     

Oral delivery of shRNA and siRNA via multifunctional polymeric nanoparticles for synergistic cancer therapy

Galactose modified trimethyl chitosan-cysteine (GTC) conjugates with various galactose grafting densities were developed for oral delivery of Survivin shRNA-expression pDNA (iSur-pDNA) and vascular endothelial growth factor (VEGF) siRNA (siVEGF) in the synergistic and targeted treatment of hepatoma. iSur-pDNA and siVEGF loaded GTC nanoparticles (NPs) were prepared via electrostatic complexation and showed desirable stability in physiological fluids and improved intestinal permeation compared to naked genes. Galactose grafting density of GTC NPs significantly affected their in vitro and in vivo antitumor activities. GTC NPs with moderate galactose grafting density, termed GTC2 NPs, were superior in facilitating cellular uptake, promoting nuclear distribution, and silencing target genes, leading to notable inhibition of cell growth. In tumor-bearing mice, orally delivered GTC2 NPs could effectively accumulate in the tumor tissues and silence the expression of Survivin and VEGF, evoking increased apoptosis, inhibited angiogenesis, and thus the most efficient tumor regression. Moreover, compared with single gene delivery, co-delivery of iSur-pDNA and siVEGF showed synergistic effects on inhibiting in vitro cell proliferation and in vivo tumor growth. This study could serve as an effective approach for synergistic cancer therapy via oral gene delivery, and highlighted the importance of ligand grafting density in the rational design of targeted nanocarriers.     

Synergistic inhibition of breast cancer by co-delivery of VEGF siRNA and paclitaxel via vapreotide-modified core–shell nanoparticles

A somatostatin analog, vapreotide (VAP), can be used as a ligand for targeting drug delivery based on its high affinity to somatostatin receptors (SSTRs), which is overexpressed in many tumor cells. RNA interference plays an important role on downregulation of vascular endothelial growth factor (VEGF), which is important for tumor growth, progression and metastasis. To improve tumor therapy efficacy, the vapreotide-modified core–shell type nanoparticles co-encapsulating VEGF targeted siRNA (siVEGF) and paclitaxel (PTX), termed as VAP-PLPC/siRNA NPs, were developed in this study. When targeted via somatostatin receptors to tumor cells, the VAP-PLPC/siRNA NPs could simultaneously delivery siVEGF and PTX into cells and achieve a synergistic inhibition of tumor growth. Interestingly, in vitro cell uptake and gene silencing experiments demonstrated that the targeted VAP-PLPC/siRNA NPs exhibited significant higher intracellular siRNA accumulation and VEGF downregulation in human breast cancer MCF-7 cells, compared to those of the non-targeted PEG-PLPC/siRNA NPs. More importantly, in vivo results further demonstrated that the targeted VAP-PLPC/siRNA NPs had significant stronger drug distribution in tumor tissues and tumor growth inhibition efficacy via receptor-mediated targeting delivery, accompany with an obvious inhibition of neovascularization induced by siVEGF silencing. These results suggested that the co-delivery of siRNA and paclitaxel via vapreotide-modified core–shell nanoparticles would be a promising approach for tumor targeted therapy.     

Synergistic effects of dual Zn/Ag ion implantation in osteogenic activity and antibacterial ability of titanium

Zinc (Zn) and silver (Ag) are co-implanted into titanium by plasma immersion ion implantation. A Zn containing film with Ag nanoparticles (Ag NPs) possessing a wide size distribution is formed on the surface and the corrosion resistance is improved due to the micro-galvanic couples formed by the implanted Zn and Ag. Not only are the initial adhesion, spreading, proliferation and osteogenic differentiation of rBMSCs observed from the Zn/Ag implanted Ti in vitro, but also bacteria killing is achieved both in vitro and in vivo. Electrochemical polarization and ion release measurements suggest that the excellent osteogenic activity and antibacterial ability of the Zn/Ag co-implanted titanium are related to the synergistic effect resulting from the long-range interactions of the released Zn ions and short-range interactions of the embedded Ag NPs. The Zn/Ag co-implanted titanium offers both excellent osteogenic activity and antibacterial ability and has large potential in orthopedic and dental implants.     

Polyethyleneimine-mediated synthesis of folic acid-targeted iron oxide nanoparticles for in vivo tumor MR imaging

We report a facile polyethyleneimine (PEI)-mediated approach to synthesizing folic acid (FA)-targeted magnetic iron oxide nanoparticles (Fe₃O₄ NPs) for in vivo magnetic resonance (MR) imaging of tumors. In this study, stable PEI-coated Fe₃O₄ NPs were prepared by a one-pot hydrothermal route. The aminated Fe₃O₄ NPs with PEI coating enabled covalent conjugation of fluorescein isothiocyanate (FI) and folate-conjugated polyethylene glycol (PEG) with one end of carboxyl groups (FA-PEG-COOH). Followed by final acetylation, FA-targeted PEGylated Fe₃O₄ NPs (Fe₃O₄-PEI-Ac-FI-PEG-FA NPs) were formed. The formed multifunctional Fe₃O₄ NPs were characterized via different techniques. We show that the PEI-mediated approach along with the PEGylation conjugation enables the generation of water-dispersible and stable multifunctional Fe₃O₄ NPs, and the particles are quite cytocompatible and hemocompatible in the given concentration range as confirmed by in vitro cytotoxicity assay, cell morphology observation, and hemolysis assay. In addition, flow cytometry and confocal microscopy data show that the multifunctional Fe₃O₄ NPs are able to target a model cancer cell line (KB cells) overexpressing FA receptors in vitro. Importantly, the FA-targeted Fe₃O₄ NPs are able to be used as an efficient nanoprobe for MR imaging of cancer cells in vitro and a xenografted tumor model in vivo via an active FA targeting pathway. With the facile PEI-mediated formation strategy and PEGylation conjugation chemistry, the Fe₃O₄ NPs may be multifunctionalized with other biological ligands for MR imaging of different biological systems.     

Polybutylcyanoacrylate nanoparticles for delivering hormone response element-conjugated neurotrophin-3 to the brain of intracerebral hemorrhagic rats

Hypertensive intracerebral hemorrhage (ICH) is a rapidly evolutional pathology, inducing necrotic cell death followed by apoptosis, and alters gene expression levels in surrounding tissue of an injured brain. For ICH therapy by controlled gene release, the development of intravenously administrable delivery vectors to promote the penetration across the blood–brain barrier (BBB) is a critical challenge. To enhance transfer efficiency of genetic materials under hypoxic conditions, polybutylcyanoacrylate (PBCA) nanoparticles (NPs) were used to mediate the intracellular transport of plasmid neurotrophin-3 (NT-3) containing hormone response element (HRE) with a cytomegalovirus (cmv) promoter and to differentiate induced pluripotent stem cells (iPSCs). The differentiation ability of iPSCs to neurons was justified by various immunological stains for protein fluorescence. The effect of PBCA NP/cmvNT-3-HRE complexes on treating ICH rats was studied by immunostaining, western blotting and Nissl staining. We found that the treatments with PBCA NP/cmvNT-3-HRE complexes increased the capability of differentiating iPSCs to express NT-3, TrkC and MAP-2. Moreover, PBCA NPs could protect cmvNT-3-HRE against degradation with EcoRI/PstI and DNase I in vitro and raise the delivery across the BBB in vivo. The administration of PBCA NP/cmvNT-3-HRE complexes increased the expression of NT-3, inhibited the expression of apoptosis-inducing factor, cleaved caspase-3 and DNA fragmentation, and reduced the cell death rate after ICH in vivo. PBCA NPs are demonstrated as an appropriate delivery system for carrying cmvNT-3-HRE to the brain for ICH therapy.     

Iron/iron oxide core/shell nanoparticles for magnetic targeting MRI and near-infrared photothermal therapy

The development of photothermal agents (PTAs) with good stability, low toxicity, highly targeting ability and photothermal conversion efficiency is an essential pre-requisite to near-infrared photothermal therapy (PTT) in vivo. Herein, we report the readily available PEGylated Fe@Fe₃O₄ NPs, which possess triple functional properties in one entity – targeting, PTT, and imaging. Compared to Au nanorods, they exhibit comparable photothermal conversion efficiency (∼20%), and much higher photothermal stability. They also show a high magnetization value and transverse relaxivity (∼156 mm⁻¹ s⁻¹), which should be applied for magnetic targeting MRI. With the Nd-Fe-B magnet (0.5 T) beside the tumour for 12 h on the xenograft HeLa tumour model, PEGylated Fe@Fe₃O₄ NPs exhibit an obvious accumulation. In tumour, the intensity of MRI signal is ∼ three folds and the increased temperature is ∼ two times than those without magnetic targeting, indicating the good magnetic targeting ability. Notably, the intrinsic high photothermal conversion efficiency and selective magnetic targeting effect of the NPs in tumour play synergistically in highly efficient ablation of cancer cells in vitro and in vivo.     

Nanoparticle toxicity assessment using an in vitro 3-D kidney organoid culture model

Nanocarriers and nanoparticles remain an intense pharmaceutical and medical imaging technology interest. Their entry into clinical use is hampered by the lack of reliable in vitro models that accurately predict in vivo toxicity. This study evaluates a 3-D kidney organoid proximal tubule culture to assess in vitro toxicity of the hydroxylated generation-5 PAMAM dendrimer (G5-OH) compared to previously published preclinical in vivo rodent nephrotoxicity data. 3-D kidney proximal tubule cultures were created using isolated murine proximal tubule fractions suspended in a biomedical grade hyaluronic acid-based hydrogel. Toxicity in these cultures to neutral G5-OH dendrimer nanoparticles and gold nanoparticles in vitro was assessed using clinical biomarker generation. Neutral PAMAM nanoparticle dendrimers elicit in vivo-relevant kidney biomarkers and cell viability in a 3-D kidney organoid culture that closely reflect toxicity markers reported in vivo in rodent nephrotoxicity models exposed to this same nanoparticle.     

Combined mTOR inhibitor rapamycin and doxorubicin-loaded cyclic octapeptide modified liposomes for targeting integrin α3 in triple-negative breast cancer

A novel therapeutic strategy combining mTOR inhibitor rapamycin (RAPA) and doxorubicin (DOX)-loaded cyclic octapeptide liposomes for targeting integrin α3 was expected to combat the triple-negative breast cancer (TNBC). RAPA was loaded into PEG–PCL polymer micelles (M-RAPA) to realize solubilization. Flow cytometry analysis and laser confocal microscopy were used to evaluate the in vitro cellular uptake. The in vivo tumor targeting and bio-distribution were investigated by living fluorescence imaging. As the results, LXY modification significantly enhanced the cellular uptake of liposomal DOX in integrin α3 overexpressed TNBC cells (MDA-MB-231) in vitro and accordingly improved the tumor accumulation of liposomes in vivo. When used alone or in combination with LXY-LS-DOX, M-RAPA could greatly inhibit the expression of HIF-1α protein, which is always highly expressed in malignant cancers and involved in tumor angiogenesis, proliferation, therapeutic resistance and poor prognosis. Meanwhile, the improved efficacy of combined targeted therapy with LXY-LS-DOX and M-RAPA was demonstrated by the in vitro cytotoxicity against model TNBC cells and in vivo anti-tumor activity against mouse bearing TNBC model. These results suggested that the targeted combinational therapy based on LXY-LS-DOX and M-RAPA systems may provide a rational strategy to improve therapeutic outcomes of TNBC.     

The impact of PLGA scaffold orientation on in vitro cartilage regeneration

The success of in vitro cartilage regeneration provides a promising approach for cartilage repair. However, the currently engineered cartilage in vitro is unsatisfactory for clinical application due to non-homogeneous structure, inadequate thickness, and poor mechanical property. It has been widely reported that orientation of scaffolds can promote cell migration and thus probably contributes to improving tissue regeneration. This study explored the impact of microtubular oriented scaffold on in vitro cartilage regeneration. Porcine articular chondrocytes were seeded into microtubule-oriented PLGA scaffolds and non-oriented scaffolds respectively. A long-term in vitro culture followed by a long-term in vivo implantation was performed to evaluate the influence of scaffold orientation on cartilage regeneration. The current results showed that the oriented scaffolds could efficiently promote cell migration towards the inner region of the constructs. After 12 weeks of in vitro culture, the chondrocyte-scaffold constructs in the oriented group formed thicker cartilage with more homogeneous structure, stronger mechanical property, and higher cartilage matrix content compared to the non-oriented group. Furthermore, the in vitro engineered cartilage based on oriented scaffolds showed better cartilage formation in terms of size, wet weight, and homogeneity after 12-week in vivo implantation in nude mice. These results indicated that the longitudinal microtubular orientation of scaffolds can efficiently improve the structure and function of in vitro engineered cartilage.     

Near-infrared fluorescence imaging using organic dye nanoparticles

Near-infrared (NIR) fluorescence imaging in the 700–1000 nm wavelength range has been very attractive for early detection of cancers. Conventional NIR dyes often suffer from limitation of low brightness due to self-quenching, insufficient photo- and bioenvironmental stability, and small Stokes shift. Herein, we present a strategy of using small-molecule organic dye nanoparticles (ONPs) to encapsulate NIR dyes to enable efficient fluorescence resonance energy transfer to obtain NIR probes with remarkably enhanced performance for in vitro and in vivo imaging. In our design, host ONPs are used as not only carriers to trap and stabilize NIR dyes, but also light-harvesting agent to transfer energy to NIR dyes to enhance their brightness. In comparison with pure NIR dyes, our organic dye nanoparticles possess almost 50-fold increased brightness, large Stokes shifts (∼250 nm) and dramatically enhanced photostability. With surface modification, these NIR-emissive organic nanoparticles have water-dispersity and size- and fluorescence- stability over pH values from 2 to 10 for almost 60 days. With these superior advantages, these NIR-emissive organic nanoparticles can be used for highly efficient folic-acid aided specific targeting in vivo and ex vivo cellular imaging. Finally, during in vivo imaging, the nanoparticles show negligible toxicity. Overall, the results clearly display a potential application of using the NIR-emissive organic nanoparticles for in vitro and in vivo imaging.