Nanocarriers from GRAS Zein Proteins to Encapsulate Hydrophobic Actives

Brij-stabilized zein nanoparticles as potential drug carriers

The current study was designed to provide a preliminary physico-chemical characterization of zein nanosystems prepared with various Brij surfactants (for the first time to the best of our knowledge) as a function of various external stimuli such as temperature, pH, serum incubation and the freeze-drying process. The results demonstrate that when Brijs are characterized by unsaturation (C18), considerable stabilization of the colloidal structure is promoted while the length of the polyethylene glycol fraction does not significantly modulate the physico-chemical properties of the nanosystems. Specifically, dynamic light scattering and nanoparticle tracking analysis demonstrated that the use of 0.2 % w/v of Brij O10 promoted the formation of stable zein nanosystems with mean sizes of ∼150 nm and a narrow size distribution, preserving their structures at various pHs and temperatures. The use of mannitol as cryoprotectant resulted in a formulation that can easily be re-suspended in water after the freeze-drying process. This nanoformulation demonstrated that it efficiently retained different amounts of both hydrophilic and lipophilic compounds and showed a prolonged release of the entrapped molecules. In addition, the nanosystems showed a favorable degree of in vitro safety on various cell lines when a concentration <50 μg/mL of protein was used, demonstrating the potential application of Brij O10-stabilized zein nanoparticles as innovative nanocarriers of several active compounds.

Fabrication, Characterization, and Formation Mechanism of Zein-Gum Arabic Nanocomposites in Aqueous Ethanol Solution with a High Ethanol Content

The antisolvent precipitation method is widely applied to produce zein colloidal particles. The process involves dissolving zein in 55-90% (v/v) alcohol/water mixtures and then shearing such solutions into deionized water to lower the ethanol content. In the present work, on the basis of the preliminary result that gum arabic (GA) was able to well disperse in 70% (v/v) alcohol/water mixtures, a new way was created to produce zein-GA nanocomposites by simply mixing their aqueous alcohol solution with a high alcohol level of 70% (v/v) at pH 8.0. Findings showed that the multimodal size distribution of zein or GA alone was shifted to be the monomodal peak after zein and GA aqueous ethanol solution was mixed, indicating the successful formation of zein-GA nanocomposites. A core-shell structure was observed for zein-GA nanocomposites, with zein as a core and GA as a shell. In addition, the incorporation of GA caused the conformational and second structural changes of zein. A two-step mechanism was involved to explain the formation of zein-GA nanocomposites. The first step was that GA addition changed the polarity of zein aqueous ethanol solution and zein nanoparticles formed, and the second step was that hydrogen bonds and hydrophobic interactions promoted the adsorption of GA onto the particle surfaces. Results in this work would provide a new sight into the design of zein-based nanocomplexes, which may have potential applications, such as constructing delivery systems, for bioactive compounds.

Fabrication of Composite Structures of Lysozyme Fibril-Zein using Antisolvent Precipitation: Effects of Blending and pH Adjustment Sequences

Antisolvent precipitation is a widely used method to fabricate prolamin-based composites. In the present study, composite structures of lysozyme amyloid fibrils with zein proteins were fabricated using the antisolvent precipitation method by applying different blending and pH adjustment sequences. Globular prolamins were bound to the amyloid fibrils to combine their respective advantages. The dynamic light scattering showed that the composites with a characteristic stabilized behavior (43.60 ± 1.75 mV ∼ 35.20 ± 0.65 mV) were formed at pH 4.0-5.0, in which noncovalent interactions between fibril and particles occurred. Two different structures: fruit tree-like structure and beaded-like structure, were presented in AFM and TEM images due to the different pH adjustment sequences, while blending sequences had negligible effect on the morphology of the composites. A fruit tree-like entity was detected for lysozyme fibril-zein composites, where its "branches" bear zein globular particles. A beaded-like structure was observed for lysozyme fibril-zein composites, where lysozyme fibril was the thread and zein aggregates were the beads. The potential mechanism of this phenomenon can be explained as the fruit tree-like structure being primarily formed through electrostatic interactions while the beaded-like structure is mainly caused by hydrophobic interactions. The composites of fruit tree-like structures hold a more promising stability than those with beaded-like structures. The results of this research would give constructive information for the fabrication of amyloid fibril-prolamin protein composites, which may exhibit the combined advantages of each components and have potential applications in encapsulation and protection of bioactive substances and stabilizing emulsions.

Food Protein-Based Nanodelivery Systems for Hydrophobic and Poorly Soluble Compounds

The hydrophobicity of bioactive molecules poses a considerable problem in the pharmaceutical and the food industry. Using food-based protein nanocarriers is one promising way to deliver hydrophobic molecules. These types of protein possess many functional properties such as surface activity, water-binding capacity, emulsification, foaming, gelation, and antioxidant activity, as well as their incorporation in the food industry as ingredients. Besides, they express low toxicity, are less expensive compared to synthetic polymers, and are biodegradable. This review aims to give a brief overview of the recent studies done using food proteins as colloidal delivery systems for hydrophobic and poorly soluble compounds.

Emergence in protein derived nanomedicine as anticancer therapeutics: More than a tour de force

Cancer has thwarted as a major health problem affecting the global population. With an alarming increase in the patient population suffering from diverse varieties of cancers, the global demographic data predicts sharp escalation in the number of cancer patients. This can be expected to reach 420 million cases by 2025. Among the diverse types of cancers, the most frequently diagnosed cancers are the breast, colorectal, prostate and lung cancer. From years, conventional treatment approaches like surgery, chemotherapy and radiation therapy have been practiced. In the past few years, increasing research on molecular level diagnosis and treatment of cancers have significantly changed the realm of cancer treatment. Lately, uses of advanced chemotherapy and immunotherapy like treatments have gained significant progress in the cancer therapy, but these approaches have several limitations on their safety and toxicity. This has generated lot of momentum for the evolution of new drug delivery approaches for the effective delivery of anticancer therapeutics, which may improve the pharmacokinetic and pharmacodynamic effect of the drugs along with significant reduction in the side effects. In this regard, the protein-based nano-medicines have gained wider attention in the management of cancer. Proteins are organic macromolecules essential, for life and have quite well explored in developing the nano-carriers. Furthermore, it provides passive or active tumour cell targeted delivery, by using protein based nanovesicles or virus like structures, antibody drug conjugates, viral particles, etc. Moreover, by utilizing various formulation strategies, both the animal and plant derived proteins can be converted to produce self-assembled virus like nano-metric structures with high efficiency in targeting the metastatic cancer cells. Therefore, the present review extensively discusses the applications of protein-based nano-medicine with special emphasis on intracellular delivery/drug targeting ability for anticancer drugs.

Single-Step Self-Assembly and Physical Crosslinking of PEGylated Chitosan Nanoparticles by Tannic Acid

Chitosan-based nanoparticles are promising materials for potential biomedical applications. We used Flash NanoPrecipitation as a rapid, scalable, single-step method to achieve self-assembly of crosslinked chitosan nanoparticles. Self-assembly was driven by electrostatic interactions, hydrogen bonding, and hydrophobic interactions; tannic acid served to precipitate chitosan to seed nanoparticle formation and crosslink the chitosan to stabilize the resulting particles. The size of the nanoparticles can be tuned by varying formulation parameters including the total solids concentration and block copolymer to core mass ratio. We demonstrated that hydrophobic moieties can be incorporated into the nanoparticle using a lipophilic fluorescent dye as a model system.

Amorphous nanoparticles by self-assembly: processing for controlled release of hydrophobic molecules

More than 40% of newly developed drug molecules are highly hydrophobic and, thus, suffer from low bioavailability. Kinetically trapping the drug as a nanoparticle in an amorphous state enhances solubility. However, enhanced solubility can be compromised by subsequent recrystallization from the amorphous state during drying processes. We combine Flash NanoPrecipitation (FNP) to generate nanoparticles with spray-drying to produce stable solid powders. We demonstrate that the continuous nanofabrication platform for nanoparticle synthesis and recovery does not compromise the dissolution kinetics of the drug. Lumefantrine, an anti-malaria drug, is highly hydrophobic with low bioavailability. Increasing the bioavailability of lumefantrine has the potential to reduce the dose and number of required administrations per treatment, thus reducing cost and increasing patient compliance. The low melting temperature of lumefantrine (Tm = 130 °C) makes the drying of amorphous nanoparticles at elevated temperatures potentially problematic. Via FNP, we produced 200-400 nm nanoparticles using hydroxypropyl methylcellulose acetate succinate (HPMCAS), lecithin phospholipid, and zein protein stabilizers. Zein nanoparticles were spray-dried at 100 °C and 120 °C to study the effect of the drying temperature. For zein powders, at two hours the dissolution kinetics under fasted conditions reached 85% release for the 100 °C sample, but only 60% release for the 120 °C sample. Powder X-ray diffraction, differential scanning calorimetry, and solid state nuclear magnetic resonance indicate that the lumefantrine in the nanoparticle core is amorphous for samples spray-dried at 100 °C. Dissolution under fed state conditions showed similar release kinetics for both temperatures, with 90-95% release at two hours. Zein and HPMCAS nanoparticles spray-dried at 100 °C showed release profiles in fasted and fed state media that are identical to those of lyophilized samples, i.e. those dried at cryogenic conditions where no transformation to the crystalline state can occur. Thus, spray drying 30 °C below the melting transition of lumefantrine is sufficient to maintain the amorphous state. These inexpensive formulations have potential to be developed into future therapies for malaria, and the results also highlight the potential of combining FNP and spray-drying as a versatile platform to assemble and rapidly recover amorphous nanoparticles in a solid dosage form.

Preparation and characterization of α-tocopherol nanocapsules based on gum Arabic-stabilized nanoemulsions

The preparation of water dispersed α-tocopherol nanocapsules through solvent-displacement technique using gum Arabic (GA) as natural stabilizing and emulsifying biopolymer, for a first time was aimed in current research. The effects of GA concentrations on physicochemical and biological characteristics of prepared nanocapsules, namely, mean particle size, size distribution, zeta potential, rheological properties, turbidity, in vitro antioxidant activity and cellular uptake were evaluated, subsequently. The result indicated that the mono modal size distributed water dispersible α-tocopherol nanocapsules could be successfully attained using selected technique in sizes ranged from 10.01 to 171.2 nm and zeta potential of - 13.5 to - 47.8 mv. The prepared nanocapsules showed the dilatant rheological properties and acceptable radical scavenging (antioxidant activity). The cellular uptake of samples were increased up to 12 times more than microsized α-tocopherol. Consequently, the prepared water dispersed nanosized α-tocopherol can effectively be used in water based food and beverage formulations as nutrition enhancer or natural preservatives.

Copper Loading of Preformed Nanoparticles for PET-Imaging Applications

Nanoparticles (NP) are promising contrast agents for positron emission tomography (PET) radionuclide imaging that can increase signal intensity by localizing clusters of PET radionuclides together. However, methods to load NPs with PET radionuclides suffer from harsh loading conditions or poor loading efficacies or result in NP surface modifications that alter targeting in vivo. We present the formation of water-dispersible, polyethylene glycol coated NPs that encapsulate phthalocyanines into NP cores at greater than 50 wt % loading, using the self-assembly technique Flash NanoPrecipitation. Particles from 70 to 160 nm are produced. Phthalocyanine NPs rapidly and spontaneously chelate metals under mild conditions and can act as sinks for PET radionuclides such as 64-Cu to produce PET-active NPs. NPs chelate copper(II) with characteristic rates of 1845 M^-1 h^-1 at pH 6 and 37 °C, which produced >90% radionuclide chelation within 1 h. NP physical properties, such as core composition, core fluidity, and size, can be tuned to modulate chelation kinetics. These NPs retain ⁶⁴Cu even in the presence of the strong chelator ethylene diamine tetraacetic acid. The development of these constructs for rapid and facile radionuclide labeling expands the applications of NP-based PET imaging.

Design and Solidification of Fast-Releasing Clofazimine Nanoparticles for Treatment of Cryptosporidiosis

Clofazimine, a lipophilic (log P = 7.66) riminophenazine antibiotic approved by the US Food and Drug Administration (FDA) with a good safety record, was recently identified as a lead hit for cryptosporidiosis through a high-throughput phenotypic screen. Cryptosporidiosis requires fast-acting treatment as it leads to severe symptoms which, if untreated, result in morbidity for infants and small children. Consequently, a fast-releasing oral formulation of clofazimine in a water-dispersible form for pediatric administration is highly desirable. In this work, clofazimine nanoparticles were prepared with three surface stabilizers, hypromellose acetate succinate (HPMCAS), lecithin, and zein, using the flash nanoprecipitation (FNP) process. Drug encapsulation efficiencies of over 92% were achieved. Lyophilization and spray-drying were applied and optimized to produce redispersible nanoparticle powders. The release kinetics of these clofazimine nanoparticle powders in biorelevant media were measured and compared with those of crystalline clofazimine and the currently marketed formulation Lamprene. Remarkably improved dissolution rates and clofazimine supersaturation levels up to 90 times equilibrium solubility were observed with all clofazimine nanoparticles tested. Differential scanning calorimetry indicated a reduction of crystallinity of clofazimine in nanoparticles. These results strongly suggest that the new clofazimine nanoparticles prepared with affordable materials in this low-cost nanoparticle formulation process can be used as viable cryptosporidiosis therapeutics.

Small amphipathic peptides are responsible for the assembly of cruciferin nanoparticles

Amphipathic peptides are versatile building blocks for fabricating well-ordered nanostructures, which have gained much attention owing to their enormous design possibilities and bio-functionalities. However, using amphipathic peptides from natural proteins to create tunable nanostructures is challenging because of their heterogeneity and great tendency to form aggregates. Here we fabricated two well-defined nanoparticles from cruciferin amphipathic peptides by integrating top-down and bottom-up approach. Alkali hydrolysis (pH 12, 120 °C for 30 min) was introduced to break down intact cruciferin into peptides (top–down). The cruciferin peptides and their fractions were then assembled into nanoparticles (bottom–up) in the presence of calcium ions. The permeate fraction from 10 kDa cut-off membrane formed smaller nanoparticles (F1-NPs) (around 82 nm) than that of unfractionated cruciferin peptides (CRU-NPs, around 185 nm); the electrostatic and hydrophobic interactions were the main driving forces for particle formation. LC-MS/MS analysis characterised that the small amphipathic peptides (X_n1Z_n2X_n3Z_n4, n_1–4 = 0~5), composed of alternating hydrophobic (X) and hydrophilic (Z) amino acid with a length of 5–15 and 5–20 residues for F1-NPs and CRU-NPs, respectively, were responsible for particle formation. Our study established the mechanism of particle formation of the cold gelation is through assembly of amphipathic peptides.

Assembly of Macrocycle Dye Derivatives into Particles for Fluorescence and Photoacoustic Applications

Optical imaging is a rapidly progressing medical technique that can benefit from the development of new and improved optical imaging agents suitable for use in vivo. However, the molecular rules detailing what optical agents can be processed and encapsulated into in vivo presentable forms are not known. We here present the screening of series of highly hydrophobic porphyrin, phthalocyanine, and naphthalocyanine dye macrocycles through a self-assembling Flash NanoPrecipitation process to form a series of water dispersible dye nanoparticles (NPs). Ten out of 19 tested dyes could be formed into poly(ethylene glycol) coated nanoparticles 60-150 nm in size, and these results shed insight on dye structural criteria that are required to permit dye assembly into NPs. Dye NPs display a diverse range of absorbance profiles with absorbance maxima within the NIR region, and have absorbance that can be tuned by varying dye choice or by doping bulking materials in the NP core. Particle properties such as dye core load and the compositions of co-core dopants were varied, and subsequent effects on photoacoustic and fluorescence signal intensities were measured. These results provide guidelines for designing NPs optimized for photoacoustic imaging and NPs optimized for fluorescence imaging. This work provides important details for dye NP engineering, and expands the optical imaging tools available for use.