Insulin- and cholic acid-loaded zein/casein-dextran nanoparticles enhance the oral absorption and hypoglycemic effect of insulin.

Diabetes mellitus is the most common metabolic disease in the world. Herein, insulin- and cholic acid-loaded zein nanoparticles with dextran surfaces were fabricated to enhance the oral absorptions of insulin in the intestine and in the liver which is the primary action organ of endogenous insulin. In the nanoparticles, zein acted as cement to embed insulin, cholic acid and casein by hydrophobic interactions. The hydrophilic dextran conjugated to casein by the Maillard reaction was located on the nanoparticle surface. The nanoparticles had an insulin loading efficiency of 74.6%, a cholic acid loading efficiency of 55.1% and a hydrodynamic diameter of 267 nm. The dextran significantly increased the disperse stability of the nanoparticles, protected the loaded insulin from hydrolysis in digestive juices, and increased the trans-mucus permeability of the insulin. The embedded cholic acid molecules were consecutively exposed to the surface when the nanoparticles were gradually eroded by proteases. The exposed cholic acid promoted the absorptions of the nanoparticles in the ileum and liver via bile acid transporters. The effect of pretreated lymphatic transport inhibitor cycloheximide revealed that about half of the nanoparticles were transported via the intestinal lymphatic transport pathway and the other half of the nanoparticles were transported via portal blood absorption. The oral pharmacological bioavailability of the nanoparticles in type I diabetic mice was 12.5-20.5%. This study demonstrates that nanoparticles are a promising oral delivery system for insulin.

Augmentation of anti-proliferative, pro-apoptotic and oxidant profiles induced by piceatannol in human breast carcinoma MCF-7 cells using zein nanostructures.

Piceatannol (PCT), a natural polyphenolic stilbene, has pleiotropic pharmacological potentials. It possesses cytotoxic activities toward variant cancerous cells. Zein nanospheres (ZN NSs) have been introduced as ideal nanostructures due to their natural origin, safety, histocompatibility. and convenient method of formulation. The purpose of this study was to explore the impact of PCT-ZN NSs formula on pharmacotherapy potential of PCT against human breast cancer MCF-7 cells. PCT-ZN NSs were formulated and characterized selectively to particle size, zeta potential, encapsulation efficiency and diffusion of PCT. The selected formula has a particle size of 84.4 ± 2.3 nm, zeta potential value of 33.8 ± 1.2 mV and encapsulation efficiency of 89.5 ± 4.1%. PCT-ZN NSs displayed significantly lower IC50 against MCF-7 cells by about 24 folds. Further, PCT-ZN NSs formula showed higher cellular uptake as compared to free PCT. Examination of cell cycle phases displayed cells accumulation in G2-M phase and increased percentage cells in pre-G1 phase indicating an apoptosis-enhancing activity. Annexin V staining indicated augmented early and late apoptosis. PCT-ZN NSs pro-apoptotic activity was confirmed by the observed significant increased mRNA expression of CASP3, p53, and Bax as well as decreased expression of Bcl2. In addition, PCT-ZN NSs induced oxidative stress as evidenced by depletion of glutathione reductase (GR) activity, increased generation of reactive oxygen species (ROS) and accumulation of lipid peroxidation products. Conclusively, ZN nanostructures of PCT revealed superior cell death-inducing activities against MCF-7 cells in comparison with free PCT. This is mediated, at least partly, by enhanced cellular uptake, pro-apoptotic activity, and oxidative stress potential.

In situ phase-changeable 2D MXene/zein bio-injection for shear wave elastography-guided tumor ablation in NIR-II bio-window.

Localized tumor photothermal cancer ablation is a minimally invasive therapeutic modality for combating cancer, but it often suffers from low therapeutic efficacy and poor precision due to the poor accumulation and non-uniform distribution of used photothermal-conversion agents in tumor tissue via the typical intravenous administration. To address this, an injectable and phase-changeable composite bio-injection consisting of biocompatible two-dimensional (2D) niobium carbide (Nb2C) MXene and the plant-originating protein, zein, has been engineered for near infrared (NIR)-II-triggered tumor photothermal ablation. Zein can respond to aqueous microenvironments and also external photo-triggers from the NIR-II bio-window (1064 nm), and transforms into a solid bio-implant after solvent exchange between ethanol and water. Which, thus, traps Nb2C MXene and heat, improving ablation efficiency and enabling the precise and complete eradication of 4T1 breast tumor cells without additional safety concerns. More significantly, shear wave elastography (SWE) as a deep-penetration imaging mode that can reflect the ablated outcomes via monitoring tissue density variation, has been employed to guide the photo-thermal ablation process to further improve the ablation precision. Thus, this compatible and phase-changeable bio-injection capable of improving photo-thermal ablation efficiency holds great potential in clinical applications.

Protein-based nanoparticles for drug delivery purposes.

Proteins represent a group of biopolymers with interesting properties to be employed as raw materials in the preparation of nanoparticles for drug delivery purposes. Due to the inherent properties of proteins (i.e., biodegradability, amphiphilic properties, etc.) the resulting nanoparticles can be considered as versatility platforms for a variety of applications. Moreover, some proteins possess a GRAS (Generally Recognized as Safe) status or are considered as excipients by different Regulatory Agencies. As result of this, the resulting nanoparticles and potential translation to clinic would be facilitated, compared to other materials (i.e., polymers). This review is focused on the main proteins employed in the preparation of nanoparticles as well as the procedures permitting their transformation into nanoparticles able of accommodating a high variety of bioactive compounds and drugs. Moreover, the review also provides examples of application of nanoparticles prepared from albumins, globulins, prolamins or macromolecules derived from proteins.

Design of Zein Conjugation and Surface Modification for Targeting Drug Delivery.

Various strategies for the use of zein for controlled drug release have been investigated and reported in the literature, especially engineering strategies for using zein conjugates to enhance oral bioavailability and targeted delivery, which has attracted interest in recent research. Although still limited, the ability to fabricate self-assembling nanoparticles loaded with molecules of interest offering functional groups for potential conjugation could yield zein-based conjugates with promise as materials for drug delivery. In the current review, recent studies on zein-based conjugates with outstanding features are discussed based on the various types of conjugation. The key physicochemical characterization methods for the chemical conjugation and identification of zein are also summarized. Further opportunities to develop zein-based materials through conjugation will provide promising alternative formulations for a number of drug candidates.

Dietary wheat amylase trypsin inhibitors promote features of murine non-alcoholic fatty liver disease.

We previously demonstrated that a common dietary protein component, wheat amylase trypsin inhibitors (ATI), stimulate intestinal macrophages and dendritic cells via toll like receptor 4. Activation of these intestinal myeloid cells elicits an inflammatory signal that is propagated to mesenteric lymph nodes, and that can facilitate extraintestinal inflammation. Mice were fed a well-defined high fat diet, with (HFD/ATI) or without (HFD) nutritionally irrelevant amounts of ATI. Mice on HFD/ATI developed only mild signs of intestinal inflammation and myeloid cell activation but displayed significantly higher serum triglycerides and transaminases compared to mice on HFD alone. Moreover, they showed increased visceral and liver fat, and a higher insulin resistance. ATI feeding promoted liver and adipose tissue inflammation, with M1-type macrophage polarization and infiltration, and enhanced liver fibrogenesis. Gluten, the major protein component of wheat, did not induce these pathologies. Therefore, wheat ATI ingestion in minute quantities comparable to human daily wheat consumption exacerbated features of the metabolic syndrome and non-alcoholic steatohepatitis, despite its irrelevant caloric value.

Drug stabilization in the gastrointestinal tract and potential applications in the colonic delivery of oral zein-based formulations.

In recent years, various oral dosage forms using biomaterials have been developed to deliver drugs to the colon for therapy due to the advantages of local treatment and its ideal location for drug delivery. To achieve site-specific delivery, the complete drug should be released in the colon, while the drug must be protected or their delivery minimized in the stomach and small intestine. The use of natural or synthetic polymers has been reported for these purposes. The roles of zein in drug delivery have been identified with various types of formulations for improving bioavailability, controlled drug release and targeted delivery. Although zein has been demonstrated as a potential material for pharmaceutical applications, a review of zein in the gastrointestinal tract for stabilizing drug- and colon-specific delivery is still missing. In the present review, we aim to provide typical strategies for using zein in formulations to minimize drug release/ensure drug protection in the upper part of the gastrointestinal tract. Furthermore, effective fabrications or modifications for drug release in the colon will be highlighted. This primary resource of related methods of using zein in the gastrointestinal tract will advance technologies for using it as a natural polymer for drug delivery.

Rapamycin loaded TPGS-Lecithins-Zein nanoparticles based on core-shell structure for oral drug administration.

Rapamycin as a novel macrolide immunosuppressive agent has been commonly used in organ transplantation owing to its stronger immunosuppressive effect, non-nephrotoxicity and lower side effect. However its drawbacks of low bioavailability and big individual difference remain to be improved in clinical application. Here rapamycin loaded TPGS-Lecithins-Zein nanoparticles (RTLZ-NPs) with core-shell structure were prepared by the phase separation method. The RTLZ-NPs were approximately 190.3 nm in size, with PDI and zeta potential about 0.256 and -19.71 mV respectively. Drug entrapment and loading achieved were about 86.64 and 25.73% respectively. Meanwhile RTLZ-NPs exhibited favorable enzymolysis resistance abilities in gastrointestinal environments and enhanced uptake in Caco-2 cells. The optimum absorption sites of rapamycin in the intestine were duodenum and jejunum as single-pass intestinal perfusion assay. Upon also considering the results of Caco-2 cell assay, it could be speculated that the transport of rapamycin in vivo involved active transport as well as P-glycoprotein (P-gp) based efflux. Finally, the relative oral bioavailability of RTLZ-NPS was 4.33 fold higher than free rapamycin in SD rat. Altogether the designed nanoparticles can be an efficient oral delivery strategy for rapamycin analogues to prevent the attacks from destructive enzymes, reduce cell efflux, increase cell uptake, and then enhance the oral bioavailability.

Bioavailability Enhancement of Astilbin in Rats through Zein-Caseinate Nanoparticles.

Astilbin-encapsulated zein-caseinate nanoparticles were fabricated through the antisolvent method. The encapsulation and loading efficiency of astilbin in the nanoparticles were determined by high-performance liquid chromatography. The nanoparticles were characterized by particle size, ζ potential, redispersibility, scanning electron microscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy, and differential scanning calorimetry (DSC). Under the optimal formulation of astilbin, zein, and sodium caseinate with a mass ratio of 1:1:2, the size and ζ potential of the nanoparticles were 152.9 nm and -40.43 mV, respectively, while the encapsulation and loading efficiency of astilbin were 80.1 and 21.8%, respectively. The nanoparticles had good redispersibility in water without a particle size change after freeze drying. The nanoparticles showed a spherical shape with a smooth surface. XRD and DSC analyses showed that astilbin existed in amorphous form in the nanoparticles. The interactions between astilbin and the protein were found, and astilbin was encapsulated in nanoparticles rather than adsorbed. The diffusion of astilbin from nanoparticles was significantly faster than that of astilbin suspensions in both simulated gastric and intestinal fluids. Astilbin was relatively stable in simulated intestinal fluids, and the encapsulation in the nanoparticles showed a slight stability improvement effect. A pharmacokinetic study showed that the absolute bioavailability of astilbin was improved from 0.32 to 4.40% in rats through nanoparticle fabrication.

The Novel X-Ray Visible Zein-Based Non-adhesive Precipitating Liquid Embolic HEIE1_2017: An Exploratory Study.

PURPOSE: To investigate the novel zein-based non-adhesive precipitating liquid embolic HEIE1_2017. MATERIALS AND METHODS: Zein-based liquid embolics are an own class of embolization material. In this study, HEIE1_2017, a novel zein-based liquid embolic, was investigated. Visibility was assessed in vitro in CT and MRI phantoms, embolization characteristics were assessed in vivo in the kidneys of 12 pigs. Components of HEIE1_2017 were zein as occlusion material, ethanol as solvent, and iodized oil as radiopaque material. HEIE1_2017 was used in pure (HEI-PURE) and manually modified (HEI-MOD) form and compared with 6% ethylene vinyl alcohol copolymer (EVOH). Different radiological methods (CT, MRI, DSA, cone-beam CT, and micro-CT) and histopathologic analyses were applied to compare visibility and vascular occlusion patterns. RESULTS: In CT phantoms, all embolics were definitely visible as hyperdense materials. In MRI phantoms, signal-to-noise ratio was highest for HEI-PURE, followed by HEI-MOD and EVOH. In all kidneys, embolization procedures were technically successful and without complications. In DSA, all embolics were definitely visible during and after embolization. Only EVOH caused substantial artifacts in cone-beam CT and CT. In micro-CT and histopathology, HEI-PURE showed a homogeneous occlusion from segmental arteries to glomerular capillaries. HEI-MOD demonstrated the deepest vascular penetration (up to the level of peritubular capillaries), but with an inhomogeneous distribution. For EVOH, there was inhomogeneous vascular occlusion from segmental arteries to glomerular capillaries. CONCLUSION: HEIE1_2017 is a promising novel zein-based liquid embolic. Further preclinical and clinical studies with higher case numbers and long-term follow-up are needed to further assess the value of this embolic material.

Application of Box-Behnken experimental design for the formulation and optimisation of selenomethionine-loaded chitosan nanoparticles coated with zein for oral delivery.

Selenomethionine is an essential amino acid with a narrow therapeutic index and susceptibility to oxidation. Here it was encapsulated into a nanoparticle composed of chitosan cross-linked with tripolyphosphate for oral delivery. The formulation was optimised using a three-factor Box-Behnken experimental design. The chitosan:tripolyphosphate ratio, chitosan solvent pH, and drug load concentration were independently varied. The dependent variables studied were encapsulation efficiency, particle size, polydispersity index and zeta potential. For optimisation, encapsulation efficiency and zeta potential were maximised, particle diameter was set to 300 nm and polydispersity index was minimised. A 0.15 mg/mL concentration of selenomethionine, chitosan solvent pH of 3, and chitosan:tripolyphosphate ratio of 6:1 yielded optimum nanoparticles of size 187 ±â€¯58 nm, polydispersity index 0.24 ±â€¯0.01, zeta potential 36 ±â€¯6 mV, and encapsulation efficiency of 39 ±â€¯3%. Encapsulation efficiency was doubled to 80 ±â€¯1.5% by varying pH of the ionotropic solution components and by subsequent coating of the NPs with zein, increasing NP diameter to 377 ±â€¯47 nm, whilst retaining polydispersity index and zeta potential values. Selenomethionine-entrapped nanoparticles were not cytotoxic to intestinal and liver cell lines. Accelerated thermal stability studies indicated good stability of the nanoparticles under normal storage conditions (23 °C). In simulated gastrointestinal and intestinal fluid conditions, 60% cumulative release was obtained over 6 h.

Gallic acid loaded PEO-core/zein-shell nanofibers for chemopreventive action on gallbladder cancer cells.

Coaxial electrospinning was used to develop gallic acid (GA) loaded poly(ethylene oxide)/zein nanofibers in order to improve its chemopreventive action on human gallbladder cancer cells. Using a Plackett-Burman design, the effects of poly(ethylene oxide) and zein concentration and applied voltage on the diameter and morphology index of nanofibers were investigated. Coaxial nanofibers were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). GA loading efficiency as high as 77% was obtained under optimal process conditions. The coaxial nanofibers controlled GA release in acid and neutral pH medium. Cytotoxicity and reactive oxygen species (ROS) production on gallbladder cancer cell lines GB-d1 and NOZ in the presence of GA-nanofibers were assessed. GA-nanofibers triggered an increase in the cellular cytotoxicity compared with free GA on GB-d1 and NOZ cells. Statistically significant differences were found in ROS levels of GA-nanofibers compared with free GA on NOZ cells. Differently, ROS production on GB-d1 cell line was similar. Based on these results, the coaxial nanofibers obtained in this study under optimized operational conditions offer an alternative for the development of a GA release system with improved chemopreventive action on gallbladder cancer cells.

Zein Microneedles for Localized Delivery of Chemotherapeutic Agents to Treat Breast Cancer: Drug Loading, Release Behavior, and Skin Permeation Studies.

Localized delivery of chemotherapeutic agents to treat breast cancer could limit their adverse drug reactions. The aim of this study was to investigate the influence of physico-chemical properties of chemotherapeutic agents in their loading, release behavior, and skin permeation using microneedles. Zein microneedles were fabricated using the micromolding technique containing 36 microneedles in a 1-cm2 area. These microneedles were loaded with two anti-breast cancer drugs, tamoxifen and gemcitabine, having different water solubilities. Entrapment or surface coating of chemotherapeutic agents in zein microneedles was optimized to achieve greater loading efficiency. The greatest loading achieved was 607 ± 21 and 1459 ± 74 µg for tamoxifen and gemcitabine using the entrapment approach, respectively. Skin permeation studies in excised porcine skin showed that the coating on microneedles approach results in greater skin deposition for tamoxifen; while the poke-and-patch approach would provide greater skin permeation for gemcitabine. Taken together, it can be concluded that different loading strategies and skin penetration approaches have to be studied for delivery of small molecules using polymeric microneedles.

Zein-based Nanocarriers as Potential Natural Alternatives for Drug and Gene Delivery: Focus on Cancer Therapy.

Protein nanocarriers possess unique merits including minimal cytotoxicity, numerous renewable sources, and high drug-binding capability. In opposition to delivery carriers utilizing hydrophilic animal proteins, hydrophobic plant proteins (e.g, zein) have great tendency in fabricating controlled-release particulate carriers without additional chemical modification to stiffen them, which in turn evades the use of toxic chemical crosslinkers. Moreover, zein is related to a class of alcohol-soluble prolamins and generally recognized as safe (GRAS) carrier for drug delivery. Various techniques have been adopted to fabricate zein-based nanoparticulate systems including phase separation coacervation, spray-drying, supercritical anti-solvent approach, electrospinning and self-assembly. This manuscript reviews the recent advances in the zein-based colloidal nano-carrier systems such as nanospheres, nanocapsules, micelles and nanofibers with a special focus on their physicochemical characteristics and drug delivery applications.

Indirect effects of immunological tolerance to a regular dietary protein reduce cutaneous scar formation.

Oral tolerance refers to the specific inhibition of immune responsiveness to T-cell-dependent antigens contacted through the oral route before parenteral immunization. Oral tolerance to one protein does not inhibit immune responses to other unrelated proteins, but parenteral injection of tolerated antigens plus adjuvant into tolerant, but not normal, mice inhibits immune responses to antigens injected concomitantly or soon thereafter. The inhibitory effect triggered by parenteral injection of tolerated proteins is known as bystander suppression or indirect effects of oral tolerance. Intraperitoneal injection of ovalbumin (OVA) plus alum adjuvant in OVA-tolerant mice soon before skin injury inhibits inflammation and improves cutaneous wound healing. However, as OVA is not a regular component of mouse chow, we tested whether indirect effects could be triggered by zein, the main protein of corn that is regularly present in mouse chow. We show that intraperitoneal injection of a single dose (10 µg) of zein plus alum adjuvant soon before skin injury in mice reduces leucocyte infiltration but increase the number of T cells and the expression of resistin-like molecule-α (a marker of alternatively activated macrophages) in the wound bed, increases the expression of transforming growth factor-ß3 in the newly formed epidermis and reduces cutaneous scar formation. These results suggest that indirect effects of oral tolerance triggered by parenteral injection of regular dietary components may be further explored as one alternative way to promote scarless wound healing.

Green self-assembly of zein-conjugated ZnO/Cd(OH)Cl hierarchical nanocomposites with high cytotoxicity and immune organs targeting.

Inorganic nanomedicines in the fight against cancer have progressed rapidly during recent years, with the synergistic advantages of multifunctional nanosystems compared to single component. Herein, a drug-combination opinion was introduced into "nanomedicine" based on the understanding of Trojan horse-anti-tumor mechanism of inorganic nano-medicines. Moreover, we reported the green and facile synthesis route of mono-dispersed and rod-like zein-conjugated ZnO/Cd(OH)Cl hierarchical nanocomposites. We found that the nanocomposites exhibited high-efficiency killing ability to tumor cells through lipid peroxidation mediated-membrane disintegration route. The safety studies in BALB/c mice didn't detect injection anaphylaxis, hemolysis and cytotoxicity. More interestingly, the nano-composites could specially accumulate in liver and kidney, which will be helpful for targeting cure to these regional cancers.

Preparation, characterization and application of a novel biodegradable macromolecule: carboxymethyl zein.

Zein, a naturally biocompatible and biodegradable macromolecule, is widely used as plastic film material; however, the poor water solubility limits its other applications. In this study, we aimed to obtain carboxymethyl zein (CM-zein) by modifying it with sodium monochloroacetate in weakly basic environment. CM-zein showed a new FTIR peak of C-O-C bond at 1080 cm(-1), with a new signal region appearing at 4.0-4.05 ppm that assigned to the protons of the CH2 group from a carboxymethyl on (1)H NMR and a Tg of 168.0 °C by thermal analysis. Compared with the -12.3 mV of zeta potential of unmodified zein, CM-zein increased it significantly to -23.9 mV as a consequence of carboxymethylation. 5-Fluorouracil (5-FU), a model drug used in CM-zein-based tablet, was rarely detected in 0.1 mol/L HCl (pH 1.0) but it was released massively and quickly in phosphates buffer (pH 6.8) in vitro assays. The unmodified zein-based tablet illustrated much lower release level in these two fluids. Furthermore, the pharmacokinetic study of rats showed that CM-zein released 5-FU in intestine but not in stomach after dissolving. These findings indicated that CM-zein has the potential to be used for enteric preparation as a novel pH-selective biomaterial.

Electrospun antibacterial polyurethane-cellulose acetate-zein composite mats for wound dressing.

In this study, an antibacterial electrospun nanofibrous scaffolds with diameters around 400-700 nm were prepared by physically blending polyurethane (PU) with two biopolymers such as cellulose acetate (CA) and zein. Here, PU was used as the foundation polymer, was blended with CA and zein to achieve desirable properties such as better hydrophilicity, excellent cell attachment, proliferation and blood clotting ability. To prevent common clinical infections, an antimicrobial agent, streptomycin sulfate was incorporated into the electrospun fibers and its antimicrobial ability against the gram negative and gram positive bacteria were examined. The interaction between fibroblasts and the PU-CA and PU-CA-zein-drug scaffolds such as viability, proliferation, and attachment were characterized. PU-CA-zein-drug composite nanoscaffold showed enhanced blood clotting ability in comparison with pristine PU nanofibers. The presence of CA and zein in the nanofiber membrane improved its hydrophilicity, bioactivity and created a moist environment for the wound, which can accelerate wound recovery.

Oral administration of corn zein hydrolysate stimulates GLP-1 and GIP secretion and improves glucose tolerance in male normal rats and Goto-Kakizaki rats.

We have previously demonstrated that ileal administration of the dietary protein hydrolysate prepared from corn zein (ZeinH) stimulated glucagon-like peptide-1 (GLP-1) secretion and attenuated hyperglycemia in rats. In this study, to examine whether oral administration of ZeinH improves glucose tolerance by stimulating GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) secretion, glucose tolerance tests were performed in normal Sprague-Dawley male rats and diabetic Goto-Kakizaki (GK) male rats. The test solution was gavaged before ip glucose injection in normal rats or gavaged together with glucose in GK rats. Blood samples were collected from the tail vein or by using the jugular catheter to measure glucose, insulin, GLP-1, and GIP levels. In the ip glucose tolerance test, oral administration of ZeinH (2 g/kg) significantly suppressed the glycemic response accompanied by an immediate increase in plasma GLP-1 and GIP levels in normal rats. In contrast, oral administration of another dietary peptide, meat hydrolysate, did not elicit a similar effect. The glucose-lowering effect of ZeinH was attenuated by a GLP-1 receptor antagonist or by a GIP receptor antagonist. Furthermore, oral ZeinH induced GLP-1 secretion and reduced glycemic response in GK rats under the oral glucose tolerance test. These results indicate that the oral administration of the dietary peptide ZeinH improves glucose tolerance in normal and diabetic rats by its incretin-releasing activity, namely, the incretinotropic effect.

Preparation of zein conjugated quantum dots and their in vivo transdermal delivery capacity through nude mouse skin.

Zein have been successfully conjugated with quantum dots (QD630) via N-(3-dimethylaminopropyl)-N(-ethyl-carbodiimide hydrochloride (EDC) coupling. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements indicated that the average diameter of QD630 was about 5 nm, and that of the zein conjugated QD630 (QD630/Zein) increased to 24 nm. Their size distributions were relatively narrow (Polyindex (PI) < 0.15). The FT-IR and electrophoresis results indicated that QD630 has been combined with zein covalently. Uptakes of QD630 and QD630/Zein by NIH3T3 cells showed different kinetics as observed by fluorescent microscope. There was no obvious increase of fluorescent intensity within cells after 1 h for QD630 sample, while for QD630/Zein, uptake was found to be continuously increased and the major portion of QD630/Zein was localized in the perinuclear area in the form of granular inclusions at 9 h and 24 h. Moreover, penetrating ability of QD630 and QD630/Zein into skin was evaluated with nude mouse in vivo. Fluorescence images revealed that tiny QD630 particles penetrated through the stratum corneum barrier and localized within the epidermal and dermal layers by 8 h, and no QDs was found after 24 h; whereas for QD630/Zein particles, no obvious penetration was observed within 24 hours. Modification of conjugated zein to QDs may alter their skin penetration characteristics and reduce the risk of the QD toxicity.