Protection of Protein Secondary Structure by Saccharides of Different Molecular Weights during Freeze-Drying

Development of Cyclodextrin-Based Mono and Dual Encapsulated Powders by Spray Drying for Successful Preservation of Everlasting Flower Extract

The study aimed to develop encapsulation systems to maintain the preservation of everlasting (Helichrysum plicatum) flower extract polyphenols. Spray-dried encapsulates were formulated using β-cyclodextrin (BCD) and 2-hydroxypropyl-β-cyclodextrin (HPBCD) as supramolecular hosts, and their macromolecule mixtures with the conventional carriers, maltodextrin (MD) and whey protein (WP). The obtained microparticles were comparatively assessed regarding technological, physicochemical, and phytochemical properties. The highest yields were achieved by combining cyclodextrins with whey protein (73.96% for WP+BCD and 75.50% for WP+HPBCD compared to 62.48% of pure extract). The extract-carrier interactions and thermal stability were evaluated by FTIR and DSC analysis, suggesting successful entrapment within the carriers. Carriers reduced the particle diameter (3.99 to 4.86 μm compared to 6.49 μm of pure extract), classifying all encapsulates as microsystems. Carrier blends made the particle size distribution uniform, while SEM analysis revealed the production of more spherical and less aggregated particles. The HPBCD provided the highest encapsulation efficiency, with the highest content of detected aglycones and slightly lower values of their glycosylated forms. An analysis of the dual macromolecule encapsulation systems revealed the highest bioactive preservation potential for SHE+MD+BCD and SHE+WP+HPBCD. Overall, macromolecule combinations of cyclodextrins and conventional biopolymers in the spray-drying process can enhance the functional properties of H. plicatum extract.

Starch nanoparticles as a new ice crystal nucleator in Lactobacillus bulgaricus CICC 6097 cryoprotection

This work aimed at studying the cryoprotective effect of starch nanoparticles (SNPs) as ice nucleators on Lactobacillus bulgaricus CICC 6097 and exploring the protective mechanism. SNPs with a diameter of 363 nm were obtained, which possessed special properties to enhance ice nucleation and blunt ice crystals edges, and can be wrapped around the surface of bacteria form a protective barrier, thus maintaining the integrity of cell membranes and improving the survivability of L. bulgaricus CICC 6097 from 36.09% to 75.56%. However, SNCs solution formed ice crystals with obvious spikes during freezing, which was harmful to bacteria survival. Therefore, SNPs addition is a possible strategy for increasing viable cell counts during freezing. To the best of our knowledge, this report is the first to demonstrate the cryoprotective effect of ice nucleator on lactic acid bacteria.

Freeze vs. Spray Drying for Dry Wild Thyme (Thymus serpyllum L.) Extract Formulations: The Impact of Gelatin as a Coating Material

Freeze drying was compared with spray drying regarding feasibility to process wild thyme drugs in order to obtain dry formulations at laboratory scale starting from liquid extracts produced by different extraction methods: maceration and heat-, ultrasound-, and microwave-assisted extractions. Higher total powder yield (based on the dry weight prior to extraction) was achieved by freeze than spray drying and lower loss of total polyphenol content (TPC) and total flavonoid content (TFC) due to the drying process. Gelatin as a coating agent (5% w/w) provided better TPC recovery by 70% in case of lyophilization and higher total powder yield in case of spray drying by diminishing material deposition on the wall of the drying chamber. The resulting gelatin-free and gelatin-containing powders carried polyphenols in amount ~190 and 53–75 mg gallic acid equivalents GAE/g of powder, respectively. Microwave-assisted extract formulation was distinguished from the others by a higher content of polyphenols, proteins and sugars, higher bulk density and lower solubility. The type of the drying process mainly affected the position of the gelatin-derived -OH and amide bands in FTIR spectra. Spray-dried formulations compared to freeze-dried expressed higher thermal stability as confirmed by differential scanning calorimetry analysis and a higher diffusion coefficient; the last feature can be associated with the lower specific surface area of irregularly shaped freeze-dried particles (151–223 µm) compared to small microspheres (~8 µm) in spray-dried powder.

Solid Composite Material for Delivering Viable Cells into Skin Tissues via Detachable Dissolvable Microneedles

Delivering cells to desired locations in the body is needed for disease treatments, tissue repairs, and various scientific investigations such as animal models for drug development. Here, we report the solid composite material that when embedded with viable cells, can temporarily keep cells alive. Using the material, we also show the fabrication of detachable dissolvable microneedles (DMNs) that can instantly deliver viable cells into skin tissue. B16-F10-murine-melanoma (B16-F10) and human-embryonic-kidney-293T (HEK293T) cells embedded in the solid matrix of the hyaluronic/polyvinylpyrolidone/maltose (HA/PVP/maltose) mixture show 50.6 ± 12.0 and 71.0 ± 5.96% survivals, respectively, when kept at 4 °C for 24 h. Detachable DMNs made of the HA/PVP/maltose mixture and loaded with B16-F10-cells were constructed, and the obtained DMN patches could detach the cell-loaded needles into the skin within 1 min of patch application. In vivo intradermal tumorgrafting mice with the DMNs containing 800 cells of B16-F10 developed tumors 10 times bigger in volume than tumors induced by hypodermic needle injection of suspension containing 100,000 cells. We anticipate this work to be a starting point for viable cell encapsulation in the solid matrix and viable cell delivery via DMNs.

A comparative study of physicochemical and functional properties of silver carp myofibrillar protein glycated with glucose and maltodextrin

Myofibrillar protein (Mf) from silver carp (Hypophthalmichthys molitrix) was incubated with glucose and maltodextrin for 0–96 h at 50 °C and 75% relative humidity to obtain glycoconjugates in different periods of the Maillard reaction.

Role of Buffers in Protein Formulations

Buffers comprise an integral component of protein formulations. Not only do they function to regulate shifts in pH, they also can stabilize proteins by a variety of mechanisms. The ability of buffers to stabilize therapeutic proteins whether in liquid formulations, frozen solutions, or the solid state is highlighted in this review. Addition of buffers can result in increased conformational stability of proteins, whether by ligand binding or by an excluded solute mechanism. In addition, they can alter the colloidal stability of proteins and modulate interfacial damage. Buffers can also lead to destabilization of proteins, and the stability of buffers themselves is presented. Furthermore, the potential safety and toxicity issues of buffers are discussed, with a special emphasis on the influence of buffers on the perceived pain upon injection. Finally, the interaction of buffers with other excipients is examined.

Raman spectroscopy and multivariate analysis for the rapid discrimination between native-like and non-native states in freeze-dried protein formulations

This study investigates whether Raman spectroscopy combined with multivariate analysis (MVA) enables a rapid and direct differentiation between two classes of conformational states, i.e., native-like and non-native proteins, in freeze-dried formulations. A data set comprising of 99 spectra, both from native-like and various types of non-native freeze-dried protein formulations, was obtained by freeze-drying lactate dehydrogenase (LDH) as model protein under various conditions. Changes in the secondary structure in the solid freeze-dried proteins were determined through visual interpretation of the blank corrected second derivative amide I band in the ATR-FTIR spectra (further called FTIR spectra) and served as an independent reference to assign class labels. Exploratory analysis and supervised classification, using Principal Components Analysis (PCA) and Partial Least Squares - Linear Discriminant Analysis (PLS-LDA), respectively, revealed that Raman spectroscopy is with 95% accuracy able to correctly discriminate between native-like and non-native states in the tested freeze-dried LDH formulations. Backbone (i.e., amide III) and side chain sensitive spectral regions proved important for making the discrimination between both classes. As discrimination was not influenced by the spectral signals from the tested excipients, there was no need for blank corrections. The Raman model may allow direct and automated analysis of the investigated quality attribute, opening possibilities for a real time and in-line quality indication as a future step. However, the sensitivity of the method should be further investigated and where possible improved.

Vacuum foam drying: an alternative to lyophilization for biomolecule preservation

Vacuum foam drying is evaluated as an alternative for lyophilization for enhanced process and storage stability of bovine serum albumin. The protein protective efficiency of different stabilizers was compared in vacuum foam drying and lyophilization. Sucrose mixtures produced better foam characters than mannitol. Unlike calcium lactate, incorporation of polyvinyl pyrrolidone to sucrose synergistically enhanced the recovery of bovine serum albumin. The conformational stability and bovine serum albumin content further increased with sodium phosphate as compared to potassium phosphate. All sucrose mixtures, except calcium lactate showed large α-helix amide-I band at approximately 1656 cm(-1). The amorphous powder diffraction in case of sodium phosphate monobasic mixture retained maximum bovine serum albumin content. The crystallization of similar mixtures in lyophilization reduced its bovine serum albumin content. Vacuum foam drying showed better processing and storage stability of bovine serum albumin than lyophilization process. Hence vacuum foam drying is short, simple and industrially economical process for biomolecules preservation.

Biocontrol of Listeria monocytogenes and Escherichia coli O157:H7 in meat by using phages immobilized on modified cellulose membranes

The ability of phages to specifically interact with and lyse their host bacteria makes them ideal antibacterial agents. The range of applications of bacteriophage can be extended by their immobilization on inert surfaces. A novel method for the oriented immobilization of bacteriophage has been developed. The method was based on charge differences between the bacteriophage head, which exhibits an overall net negative charge, and the tail fibers, which possess an overall net positive charge. Hence, the head would be more likely to attach to positively charged surfaces, leaving the tails free to capture and lyse bacteria. Cellulose membranes modified so that they had a positive surface charge were used as the support for phage immobilization. It was established that the number of infective phages immobilized on the positively charged cellulose membranes was significantly higher than that on unmodified membranes. Cocktails of phages active against Listeria or Escherichia coli immobilized on these membranes were shown to effectively control the growth of L. monocytogenes and E. coli O157:H7 in ready-to-eat and raw meat, respectively, under different storage temperatures and packaging conditions. The phage storage stability was investigated to further extend their industrial applications. It was shown that lyophilization can be used as a phage-drying method to maintain their infectivity on the newly developed bioactive materials. In conclusion, utilizing the charge difference between phage heads and tails provided a simple technique for oriented immobilization applicable to a wide range of phages and allowed the retention of infectivity.

Mixing properties of lyophilized protein systems: a spectroscopic and calorimetric study

The purpose of this study was to investigate the solid-state properties of lyophilized formulations of protein (ribonuclease A) containing sucrose or trehalose across a wide range of compositions, both in the presence or absence of hydroxyethylstarch (HES). Infrared spectroscopy reveals that the protein forms hydrogen bonds to sugars (sucrose or trehalose) as water is removed from the sample. The strength and/or number of hydrogen bonds in dried samples increase as the weight fraction of sugar increases. Significant deviations of glass transition temperatures (T(g)'s) from those predicted by free volume theory are seen in both protein-sugar systems. The behavior can be explained by formation of protein-sugar hydrogen bonds at the expense of self-interactions between the sugars. Attractive interactions between lyophilized ribonuclease A and HES were detected spectroscopically and from thermodynamic analysis of T(g) values, contrary to the view that HES is sterically hindered from interacting with the protein surface. Sucrose-HES interactions were much less favorable than trehalose-HES interactions, suggesting that phase separation in sugar/HES/protein mixtures would be more likely in the presence of sucrose than trehalose. Finally, the thermodynamics of mixing were investigated using differential scanning calorimetry (DSC) providing some of the first data for such solid protein sugar formulations with and without HES. In nearly all samples, positive excess enthalpy, excess entropy and excess free energy were observed, with the excess free energy being greater for samples containing sucrose rather than trehalose. Analysis of Flory-Huggins chi parameters suggests that phase separation between protein and excipients may be thermodynamically favored in these dried solid preparations.

The impact of drying method and formulation on the physical properties and stability of methionyl human growth hormone in the amorphous solid state

The objective of this work was to investigate the impact of drying method and formulation on the physical stability (aggregation) and selected important physical properties of dried methionyl human growth hormone (Met-hGH) formulations. Solutions of Met-hGH with different stabilizers were dried by different methods (freeze drying, spray drying, and film drying), with and without surfactant. Properties of the dried powders included powder morphology, specific surface area (SSA), protein surface coverage, thermal analysis, and protein secondary structure. Storage stability of Met-hGH in different formulations was also studied at 50 degrees C and at 60 degrees C for 3 months. The dried powders displayed different morphologies, depending mainly on the method of drying and on the presence or absence of surfactant. Film dried powders had the lowest SSA (approximately 0.03 m(2)/g) and the lowest total protein surface accumulation (approximately 0.003%). Surfactant caused a reduction in the SSA of both spray dried and freeze dried powders. Spray dried powders showed greater protein surface coverage and SSA relative to the same formulations dried by other means. Greater in-process perturbations of protein secondary structure were observed with polymer excipients. Formulation impacted physical stability. In general, low molecular weight stabilizers provided better stability. For example, the aggregation rate at 50 degrees C of Met-hGH in a freeze dried trehalose-based formulation was approximately four times smaller than the corresponding Ficoll-70-based formulation. Drying method also influenced physical stability. In general, the film dried preparations studied showed superior stability to preparations dried by other methods, especially those formulations employing low molecular weight stabilizers.

Drying-induced variations in physico-chemical properties of amorphous pharmaceuticals and their impact on stability (I): stability of a monoclonal antibody

The present study was conducted to investigate the impact of drying method and formulation on the storage stability of IgG1. Formulations of IgG1 with varying levels of sucrose with and without surfactant were dried by different methods, namely freeze drying, spray drying, and foam drying. Dried powders were characterized by thermal analysis, scanning electron microscopy, specific surface area (SSA) analysis, electron spectroscopy for chemical analysis (ESCA), solid state FTIR, and molecular mobility measurements by both isothermal calorimetry and incoherent elastic neutron scattering. Dried formulations were subjected to storage stability studies at 40 degrees C and 50 degrees C (aggregate levels were measured by size exclusion chromatography initially and at different time points). Both drying method and formulation had a significant impact on the properties of IgG1 powders, including storage stability. Among the drying methods, SSA was highest and perturbations in secondary structure were lowest with the spray-dried preparations. Sucrose-rich foams had the lowest SSA and the lowest protein surface accumulation. Also, sucrose-rich foams had the lowest molecular mobility (both fast dynamics and global motions). Stability studies showed a log-linear dependence of physical stability on composition. Preparations manufactured by "Foam Drying" were the most stable, regardless of the stabilizer level. In protein-rich formulations, freeze-dried powders showed the poorest storage stability and the stability differences were correlated to differences in secondary structure. In stabilizer-rich formulations, stability differences were best correlated to differences in molecular mobility (fast dynamics) and total protein surface accumulation.

Effects of Excipients on Protein Conformation in Lyophilized Solids by Hydrogen/Deuterium Exchange Mass Spectrometry

PURPOSE

Excipients are added to lyophilized protein drug formulations to protect the protein during processing and storage, but the mechanisms are poorly understood. Here, hydrogen/deuterium (H/D) exchange with mass spectrometry was used to assess protein conformation and excipient interactions in lyophilized solids.

METHODS

Calmodulin (CaM, 17 kD) was co-lyophilized with carbohydrate excipients (sucrose, mannitol, trehalose, raffinose, dextran 5,000, dextran 12,000) or guanidine hydrochloride (negative control) and exposed to D2O vapor at 33% RH and RT. Samples were then dissolved and analyzed by mass spectrometry (+ESI/MS). Peptic digestion provided additional, site-specific information on H/D exchange. Solids were further characterized by powder x-ray diffraction (PXRD), differential scanning calorimetry (DSC), infrared spectroscopy (FTIR) and water vapor sorption.

RESULTS

Excipients protected CaM from H/D exchange, increasing in the order guanidine hydrochloride < no excipient, mannitol < dextran 5,000, dextran 12,000 < sucrose < raffinose < trehalose. Effects were exerted primarily in the protein's alpha-helical segments.

CONCLUSIONS

The effects of carbohydrate excipients on protein conformation in lyophilized solids are not exhibited uniformly along the protein sequence, but instead are exerted in a site-specific manner. The results also demonstrate the utility of H/D exchange with ESI/MS for protein structure characterization in lyophilized samples.

Effects of sodium tetraborate and boric acid on nonisothermal mannitol crystallization in frozen solutions and freeze-dried solids

The purpose of the present study was to elucidate the effects of sodium tetraborate (borax) and boric acid on the crystallization of mannitol in frozen aqueous solutions and freeze-dried solids. Thermal analysis of frozen solutions showed that sodium tetraborate inhibits mannitol crystallization at sodium tetraborate/mannitol molar concentration ratios of approximately 0.05, which is much lower than the other co-solutes studied (boric acid, sucrose, sodium phosphate buffer). Inhibition of the mannitol crystallization in frozen solutions resulted in highly amorphous mannitol in the freeze-dried solids. Mannitol remained in an amorphous state in some of the combination freeze-dried solids, even at elevated temperatures. Changes in the thermal transition temperatures (glass transition temperature of maximally freeze-concentrated solute ( T'g) and glass transition temperature of freeze-dried solid (Tg)) suggested reduced mannitol molecular mobility with increases in the sodium tetraborate ratio. Fourier-transform infrared spectroscopy (FT-IR) analysis of the bovine serum albumin secondary structure showed apparent protein structure-stabilizing effects of the amorphous mannitol and sodium tetraborate combination during the freeze-drying process. The mannitol and sodium tetraborate combination also protected lactate dehydrogenase (LDH) from inactivation during freeze-drying. We conclude that the complex formation and the accompanying reduction in molecular mobility make sodium tetraborate an effective mannitol crystallization inhibitor in frozen solutions and freeze-dried solids.