Carrier mediated protein and peptide stabilization

Sweet corn phytoglycogen dendrimers as a lyoprotectant for dry-state protein storage

Protein biotherapeutics typically require expensive cold-chain storage to maintain their fold and function. Packaging proteins in the dry state via lyophilization can reduce these cold-chain requirements. However, formulating proteins for lyophilization often requires extensive optimization of excipients that both maintain the protein folded state during freezing and drying (i.e., "cryoprotection" and "lyoprotection"), and form a cake to carry the dehydrated protein. Here we show that sweet corn phytoglycogens, which are glucose dendrimers, can act as both a protein lyoprotectant and a cake-forming agent. Phytoglycogen (PG) dendrimers from 16 different maize sources (PG1-16) were extracted via ethanol precipitation. PG size was generally consistent at ~70-100 nm for all variants, whereas the colloidal stability in water, protein contaminant level, and maximum density of cytocompatibility varied for PG1-16. 10 mg/mL PG1, 2, 9, 13, 15, and 16 maintained the activity of various proteins, including green fluorescent protein, lysozyme, β-galactosidase, and horseradish peroxidase, over a broad range of concentrations, through multiple rounds of lyophilization. PG13 was identified as the lead excipient candidate as it demonstrated narrow dispersity, colloidal stability in phosphate-buffered saline, low protein contaminants, and cytocompatibility up to 10 mg/mL in NIH3T3 cell cultures. All dry protein-PG13 mixtures had a cake-like appearance and all frozen protein-PG13 mixtures had a Tg' of ~ -26°C. The lyoprotection and cake-forming properties of PG13 were density-dependent, requiring a minimum density of 5 mg/mL for maximum activity. Collectively these data establish PG dendrimers as a new class of excipient to formulate proteins in the dry state.

Advances in the development of antimicrobial peptides and proteins for inhaled therapy

Antimicrobial peptides and proteins (APPs) are becoming increasingly important in targeting multidrug-resistant (MDR) bacteria. APPs is a rapidly emerging area with novel molecules being produced and further optimised to enhance antimicrobial efficacy, while overcoming issues associated with biologics such as potential toxicity and low bioavailability resulting from short half-life. Inhalation delivery of these agents can be an effective treatment of respiratory infections owing to the high local drug concentration in the lungs with lower exposure to systemic circulation hence reducing systemic toxicity. This review describes the recent studies on inhaled APPs, including in vitro and in vivo antimicrobial activities, toxicity assessments, and formulation strategies whenever available. The review also includes studies on combination of APPs with other antimicrobial agents to achieve enhanced synergistic antimicrobial effect. Since different APPs have different biological and chemical stabilities, a targeted formulation strategy should be considered for developing stable and inhalable antimicrobial peptides and proteins. These strategies include the use of sodium chloride to reduce electrostatic interaction between APP and extracellular DNA in sputum, the use of D-enantiomers or dendrimers to minimise protease-mediated degradation and or the use of prodrugs to reduce toxicity. Although great effort has been put towards optimising the biological functions of APPs, studies assessing biological stability in inhalable aerosols are scarce, particularly for novel molecules. As such, formulation and manufacture of inhalable liquid and powder formulations of APPs are underexplored, yet they are crucial areas of research for clinical translation.

Insights into Peptide Mediated Antibiofilm Treatment in Chronic Wound: A Bench to Bedside Approach

Chronic wound biofilm infections are a threat to the population with respect to morbidity and mortality. The presence of multidrug-resistant bacterial pathogens in chronic wound renders the action of antibiotics and antibiofilm agents difficult. Therefore an alternative therapy is essential for reducing bacterial biofilm burden. In this scenario, the peptide-based antibiofilm therapy for chronic wound biofilm management seeks more attention. A synthetic peptide with a broad range of antibiofilm activity against preformed and established biofilms, having the ability to kill multispecies bacteria within biofilms and possessing combinatorial activity with other antimicrobial agents, provides significant insights. In this review, we portray the possibilities and difficulties of peptide-mediated treatment in chronic wounds biofilm management and how it can be clinically translated into a product.

Dendrimers as Pharmaceutical Excipients: Synthesis, Properties, Toxicity and Biomedical Applications

The European Medicines Agency (EMA) and the Current Good Manufacturing Practices (cGMP) in the United States of America, define excipient as the constituents of the pharmaceutical form other than the active ingredient, i.e., any component that is intended to furnish pharmacological activity. Although dendrimers do not have a pharmacopoeia monograph and, therefore, cannot be recognized as a pharmaceutical excipient, these nanostructures have received enormous attention from researchers. Due to their unique properties, like the nanoscale uniform size, a high degree of branching, polyvalency, aqueous solubility, internal cavities, and biocompatibility, dendrimers are ideal as active excipients, enhancing the solubility of poorly water-soluble drugs. The fact that the dendrimer's properties are controllable during their synthesis render them promising agents for drug-delivery applications in several pharmaceutical formulations. Additionally, dendrimers can be used for reducing the drug toxicity and for the enhancement of the drug efficacy. This review aims to discuss the properties that turn dendrimers into pharmaceutical excipients and their potential applications in the pharmaceutical and biomedical fields.

Construction of Hyaluronic Tetrasaccharide Clusters Modified Polyamidoamine siRNA Delivery System

The CD44 protein, as a predominant receptor for hyaluronan (HA), is highly expressed on the surface of multiple tumor cells. HA, as a targeting molecule for a CD44-contained delivery system, increases intracellular drug concentration in tumor tissue. However, due to the weak binding ability of hyaluronan oligosaccharide to CD44, targeting for tumor drug delivery has been restricted. In this study, we first use a HA tetrasaccharide cluster as the target ligand to enhance the binding ability to CD44. A polyamidoamine (PAMAM) dendrimer was modified by a HA tetrasaccharide cluster as a nonviral vector for small interfering RNA (siRNA) delivery. The dendrimer/siRNA nanocomplexes increased the cellular uptake capacity of siRNA through the CD44 receptor-mediated endocytosis pathway, allowing the siRNA to successfully escape the endosome/lysosome. Compared with the control group, nanocomplexes effectively reduced the expression of GFP protein and mRNA in MDA-MB-231-GFP cells. This delivery system provides a foundation to increase the clinical applications of PAMAM nanomaterials.

cRGD functionalised nanocarriers for targeted delivery of bioactives

The integrins α_vβ₃ play a very imperative role in angiogenesis and are overexpressed in endothelial cells of the tumour. Recent years have witnessed huge exploration in the field of α_vβ₃ integrin-mediated bioactive targeting for treatment of cancer. In these studies, the cRGD peptide has been employed extensively owing to their binding capacity to the α_vβ₃ integrin. Principally, RGD-based approaches comprise of antagonist molecules of the RGD sequence, drug-RGD conjugates, and most importantly tethering of the nanocarrier surface with the RGD peptide as targeting ligand. Targeting tumour vasculature or cells via cRGD conjugated nanocarriers have emerged as a promising technique for delivering chemotherapeutic drugs and imaging agents for cancer theranostics. In this review, primary emphasis has been given on the application of cRGD-anchored nanocarriers for targeted delivery of drugs, imaging agents, etc. for tumour therapy.

Triptorelin Tethered Multifunctional PAMAM-Histidine-PEG Nanoconstructs Enable Specific Targeting and Efficient Gene Silencing in LHRH Overexpressing Cancer Cells

Cancer treatment using siRNA based therapies pose various limitations such as off-target effects and degradation due to lack of specific delivery in desired cells. The aim of the present study was to develop multifunctional targeted nanoconstructs, which can efficiently and precisely deliver siRNA and silence the desired gene of interest in various LHRH overexpressing cancer cells. Herein, we report the development of triblock, PAMAM-histidine-PEG dendritic nanoconstructs functionalized with triptorelin (an LHRH analog) for targeted siRNA delivery to LHRH overexpressing breast (MCF-7) and prostate (LNCaP) cancer cells. The nanoconstructs were characterized using ¹H NMR and DLS and displayed a very low cationic charge to avoid off-target interactions. The developed nanoconstructs showed negligible cytotoxicity and hemolytic activity with efficient siRNA loading, excellent serum stability, and strongly protected siRNA from degradation. Further, confocal microscopy results confirmed extremely significant (p < 0.001) higher cellular uptake of cy5.5 conjugated targeted nanoparticles (NPs) in both cancer cell lines than nontargeted NPs. Also, targeted NPs specifically delivered cy3-tagged siRNA to MCF-7 cells. Co-localization studies in MCF-7 and LNCaP cells further established that targeted NPs traveled through the endolysosomal pathway and escaped endosomes within 6 h of incubation. Gene silencing studies in luciferase expressing MCF-7 and LNCaP cell lines demonstrated that the targeted NPs exhibited extremely significant (p < 0.001) silencing of luciferase gene. Additionally, receptor blockade studies further confirmed the specificity of targeted NPs and suggested that targeted NPs entered cancer cells via LHRH receptor mediated endocytosis, which was evident through insignificant gene silencing in receptor blocked cells. Thus, the results indicated that PAMAM-histidine-PEG-triptorelin could be a promising approach for siRNA delivery, gene silencing, and tumor therapy in all LHRH overexpressing cancer cells.

Delivery systems for antimicrobial peptides

Due to rapidly increasing resistance development against conventional antibiotics, finding novel approaches for the treatment of infections has emerged as a key health issue. Antimicrobial peptides (AMPs) have attracted interest in this context, and there is by now a considerable literature on the identification such peptides, as well as on their optimization to reach potent antimicrobial and anti-inflammatory effects at simultaneously low toxicity against human cells. In comparison, delivery systems for antimicrobial peptides have attracted considerably less interest. However, such delivery systems are likely to play a key role in the development of potent and safe AMP-based therapeutics, e.g., through reducing chemical or biological degradation of AMPs either in the formulation or after administration, by reducing adverse side-effects, by controlling AMP release rate, by promoting biofilm penetration, or through achieving co-localization with intracellular pathogens. Here, an overview is provided of the current understanding of delivery systems for antimicrobial peptides, with special focus on AMP-carrier interactions, as well as consequences of these interactions for antimicrobial and related biological effects of AMP-containing formulations.

Development of acid-resistant alginate/trimethyl chitosan nanoparticles containing cationic β-cyclodextrin polymers for insulin oral delivery

In this study, the use of trimethylchitosan (TMC), by higher solubility in comparison with chitosan, in alginate/chitosan nanoparticles containing cationic β-cyclodextrin polymers (CPβCDs) has been studied, with the aim of increasing insulin uptake by nanoparticles. Firstly, TMCs were synthesized by iodomethane, and CPβCDs were synthesized within a one-step polycondensation reaction using choline chloride (CC) and epichlorohydrine (EP). Insulin-CβCDPs complex was prepared by mixing 1:1 portion of insulin and CPβCDs solutions. Then, nanoparticles prepared in a three-step procedure based on the iono-tropic pregelation method. Nanoparticles screened using experimental design and Placket Burman methodology to obtain minimum size and polydispercity index (pdI) and the highest entrapment efficiency (EE). CPβCDs and TMC solution concentration and pH and alginate and calcium chloride solution concentrations are found as the significant parameters on size, PdI, and EE. The nanoparticles with proper physicochemical properties were obtained; the size, PdI, and EE% of optimized nanoparticles were reported as 150.82 ± 21 nm, 0.362 ± 0.036, and 93.2% ± 4.1, respectively. The cumulative insulin release in intestinal condition achieved was 50.2% during 6 h. By SEM imaging, separate, spherical, and nonaggregated nanoparticles were found. In the cytotoxicity studies on Caco-2 cell culture, no significant cytotoxicity was observed in 5 h of incubation, but after 24 h of incubation, viability was decreased to 50% in 0.5 mμ of TMC concentration. Permeability studies across Caco-2 cells had been carried out, and permeability achieved in 240 min was 8.41 ± 0.39%, which shows noticeable increase in comparison with chitosan nanoparticles. Thus, according to the results, the optimized nanoparticles can be used as a new insulin oral delivery system.

Bile salts-containing vesicles: promising pharmaceutical carriers for oral delivery of poorly water-soluble drugs and peptide/protein-based therapeutics or vaccines

Most of the new drugs, biological therapeutics (proteins/peptides) and vaccines have poor performance after oral administration due to poor solubility or degradation in the gastrointestinal tract (GIT). Though, vesicular carriers exemplified by liposomes or niosomes can protect the entrapped agent to a certain extent from degradation. Nevertheless, the harsh GIT environment exemplified by low pH, presence of bile salts and enzymes limits their capabilities by destabilizing them. In response to that, more resistant bile salts-containing vesicles (BS-vesicles) were developed by inclusion of bile salts into lipid bilayers constructs. The effectiveness of orally administrated BS-vesicles in improving the performance of vesicles has been demonstrated in researches. Yet, these attempts did not gain considerable attention. This is the first review that provides a comprehensive overview of utilizing BS-vesicles as a promising pharmaceutical carrier with a special focus on their successful applications in oral delivery of therapeutic macromolecules and vaccines. Insights on the possible mechanisms by which BS-vesicles improve the oral bioavailability of the encapsulated drug or immunological response of entrapped vaccine are explained. In addition, methods adopted to prepare and characterize BS-vesicles are described. Finally, the gap in the scientific researches tackling BS-vesicles that needs to be addressed is highlighted.

Druggability assessment of protein-protein interfaces

Recent success stories concerning the targeting of protein-protein interactions (PPIs) have led to an increased focus on this challenging target class for drug discovery. This article explores various avenues to assess the druggability of PPIs and describes a druggability decision flow chart, which can be applied to any PPI target. This flow chart not only covers small molecules but also peptidomimetics, peptides and conformationally restricted peptides as potential modalities for targeting PPIs. Additionally, a retrospective analysis of PPI druggability using various computational tools is summarized. The application of a systematic approach as presented in this paper will increase confidence that modulators (e.g., small organic molecules or peptides) can ultimately be identified for a particular target before a decision is made to commit significant discovery resources.

Carbon Nanomaterials: Efficacy and Safety for Nanomedicine

Carbon nanomaterials, including fullerenes, carbon nanohorns, and carbon nanotubes, are increasingly being used in various fields owing to these materials’ unique, size-dependent functions and physicochemical properties. Recently, because of their high variability and stability, carbon nanomaterials have been explored as a novel tool for the delivery of therapeutic molecules including peptide and nucleic acid cancer drugs. However, insufficient information is available regarding the safety of carbon nanomaterials for human health, even though such information is vital for the development of safe and effective nanomedicine technologies. In this review, we discuss currently available information regarding the safety of carbon nanomaterials in nanomedicine applications, including information obtained from our own studies; and we discuss types of carbon nanomaterials that demonstrate particular promise for safe nanomedicine technologies.

Preparation, statistical optimization, and in vitro characterization of insulin nanoparticles composed of quaternized aromatic derivatives of chitosan

The aim of this study was the preparation, optimization, and in vitro characterization of insulin nanoparticles composed of methylated N-(4-N,N-dimethylaminobenzyl), methylated N-(4-pyridinyl), and methylated N-(benzyl) chitosan. Three types of derivatives were synthesized by the Schiff base reaction followed by quaternization. Nanoparticles were prepared by the polyelectrolyte complexation method. Experimental design D-optimal response surface methodology was used for the optimization of the nanoparticles. Independent variables were pH of polymer solution, concentration ratio of polymer/insulin, and also polymer type. Dependent variables include size, zeta potential, polydispersity index (PdI), and entrapment efficiency (EE%). Optimized nanoparticles were studied morphologically by transmission electron microscopy (TEM), and in vitro release of insulin from nanoparticles were determined under phosphate buffer (pH = 6.8) condition. Although a quadratic model has been chosen to fit the responses for size, PdI, and EE%, the zeta potential of the particles has been best fitted to 2-FI model. The optimized nanoparticles were characterized. The size of the particles were found to be 346, 318, and 289 nm; zeta potentials were 28.5, 27.7, and 22.2 mV; PdI of particles were 0.305, 0.333, and 0.437; and calculated EE% were 70.3%, 84.5%, and 69.2%, for methylated (aminobenzyl), methylated (pyridinyl), and methylated (benzyl) chitosan nanoparticles, respectively. TEM images show separated and non-aggregated nanoparticles with sub-spherical shapes and smooth surfaces. An in vitro release study of the prepared nanoparticles showed that the cumulative percentage of insulin released from the nanoparticles were 47.1%, 38%, and 68.7% for (aminobenzyl), (pyridinyl), and (benzyl) chitosan, respectively, within 300 min.

Protein-excipient interactions: mechanisms and biophysical characterization applied to protein formulation development

The purpose of this review is to demonstrate the critical importance of understanding protein-excipient interactions as a key step in the rational design of formulations to stabilize and deliver protein-based therapeutic drugs and vaccines. Biophysical methods used to examine various molecular interactions between solutes and protein molecules are discussed with an emphasis on applications to pharmaceutical excipients in terms of their effects on protein stability. Key mechanisms of protein-excipient interactions such as electrostatic and cation-pi interactions, preferential hydration, dispersive forces, and hydrogen bonding are presented in the context of different physical states of the formulation such as frozen liquids, solutions, gels, freeze-dried solids and interfacial phenomenon. An overview of the different classes of pharmaceutical excipients used to formulate and stabilize protein therapeutic drugs is also presented along with the rationale for use in different dosage forms including practical pharmaceutical considerations. The utility of high throughput analytical methodologies to examine protein-excipient interactions is presented in terms of expanding formulation design space and accelerating experimental timelines.

Post-production protein stability: trouble beyond the cell factory

Being protein function a conformation-dependent issue, avoiding aggregation during production is a major challenge in biotechnological processes, what is often successfully addressed by convenient upstream, midstream or downstream approaches. Even when obtained in soluble forms, proteins tend to aggregate, especially if stored and manipulated at high concentrations, as is the case of protein drugs for human therapy. Post-production protein aggregation is then a major concern in the pharmaceutical industry, as protein stability, pharmacokinetics, bioavailability, immunogenicity and side effects are largely dependent on the extent of aggregates formation. Apart from acting at the formulation level, the recombinant nature of protein drugs allows intervening at upstream stages through protein engineering, to produce analogue protein versions with higher stability and enhanced therapeutic values.