Protein Drug Delivery Research Articles

Artificial Molecular Chaperone Systems for Proteins, Nucleic Acids, and Synthetic Molecules.

Molecular chaperones play critical roles in biological functions. They are closely involved in the maintenance of cell homeostasis, proper folding of proteins and nucleic acids, and inhibition of irreversible aggregation in denatured proteins. In addition to protein production, molecular chaperone function is widely recognized as important for peptide and protein drug delivery systems. Therefore, much effort has been made in recent decades to develop chaperone-mimetic molecules that have similar structures and biological functions to natural chaperones. These artificial molecular chaperone systems have been demonstrated to facilitate proper protein and nucleic acid folding, in addition to the formation of higher-order structures of synthetic molecules. Furthermore, the functions of these artificial systems show promising clinical applications in drug delivery and biomolecule detection. This topical review focuses on recent advances in the design, construction, characterization, and potential applications of different artificial molecular systems with distinct functional roles, such as the folding of water-soluble and membrane proteins, nucleic acids, and the self-assembly of synthetic molecules. Strategies used in the construction of some artificial molecule chaperone systems for proteins (such as pairs of amphiphilic molecules or self-assembled nanogels) and their applications as biomaterials are described. Specific examples from each design strategy are also highlighted to demonstrate the mechanisms, challenges, and limitations of the different artificial molecular systems. By highlighting the many new developments that have expanded the applications of the artificial chaperones beyond protein folding, this review aims to stimulate further studies on their design and applications.

Modulation of Entrapment Efficiency and In Vitro Release Properties of BSA-Loaded Chitosan Microparticles Cross-Linked with Citric Acid as a Potential Protein-Drug Delivery System.

Microparticles, aimed for oral protein and peptide drug delivery, were prepared via emulsion cross-linking using citric acid as cross-linker and polyglycerol polyricinoleate as surfactant. A comparative study of the interaction between chitosan and citric acid and its effect on the resulting microparticle properties was performed using different chitosan-to-cross-linker mass ratios and pH-values during fabrication of the microparticles. Non-cross-linked and cross-linked microparticles were studied in terms of size (4–12 μm), zeta potential (−15.7 to 12.8 mV), erosion (39.7–75.6%), a model protein encapsulation efficiency (bovine serum albumin) (6.8–27.6%), and loading capacity (10.4–40%). Fourier transform infrared spectroscopy and X-ray diffraction confirmed the ionic interaction between the protonated amine groups of chitosan and the carboxylate ions of the cross-linking agent. Scanning electron microscopy revealed that the non-cross-linked microparticles had an uneven shape with wrinkled surfaces, while the cross-linked formulations were spherical in shape with smooth surfaces. On the basis of these data, the role of the surfactant and microparticle structure on the release mechanism was proposed. Control of the microparticle shape and release mechanisms is expected to be crucial in developing carriers for the controlled delivery of proteins and peptides.

Responsive boron biomaterials and their biomedical applications

Due to the formation of dynamic boronate ester bonds between phenylboronic acid (PBA) and 1,2- and 1,3-diols, PBA-containing biomaterials show increasing applications in biomedical areas, including responsive nanobiomaterials for targeting delivery of chemical drugs, protein drugs, gene drugs and imaging agents in vitro and in vivo for detection of various bioactive molecules such as sialic acid, saccharides, adenosine triphosphate (ATP) and dopamine. With the specific reaction between PBA and sialic acid, which is overexpressed in many kinds of cancer cells, PBA has been used as a targeting moiety for tumor-targeting drug delivery. Additionally, PBA as an electron acceptor affords nanomaterials Lewis acid-base coordination with electron donor atoms such as nitrogen and oxygen, which can be exploited for developing drug delivery systems with high drug loading. Furthermore, PBA-containing materials can stoichiometric consume reactive oxygen species (ROS) and show a nucleus targeting ability. This current review outlined PBA-containing biomaterials with various responsive abilities including sialic acid-targeting, sugars-binding, ROS-response, ATP-response, dopamine-binding, and nuclear targeting. On this basis, their biomedical applications were summarized.

A Novel Oral Protein-Drug Delivery System with Bilayer Shell-Core Structure

For oral drug therapy, the inefficiency of protein/peptide drugs is a big concern due to inactivation and degradation induced by the gastric juice. In this study, a novel highly effective drug delivery system with the bilayer shell-core structure was developed for oral administration of protein/peptide drugs. In this design, chitosan microparticle was used as the carrier core to load protein drug via genipin crosslinking, and then covered by a casein protective shell via TG crosslinking to slow release the loaded drug and protect its bioactivity. In order to verify the effectiveness of this drug delivery system, the novel thrombolytic agent, nattokinase, was loaded and applied to prevent thrombosis via oral administration in mice. The results indicated that the bilayer shell-core structure could protect loaded nattokinase from destroy in the gastric juice, and then release both intact nattokinase and digested fragments with thrombolytic activity gradually in the intestine. Results from mouse black tail test indicated that oral administration of this microparticle could preclude thrombus formation in the tail. Overall, this study provides a feasible way to enhance the oral bioavailability and prolong the effective half-life of protein drugs, which has the potential to accelerate the development of oral drug therapy.

Mesoporous silica particles as potential carriers for protein drug delivery: protein immobilization and the effect of displacer on γ-globulin release

The adsorption of γ-globulin was evaluated with experiments with silica particles marketed as Syloid AL1-FP (SAL), XDP-3150 (SXDP), and 244FP (SFP). The influence of pH, pore sizes, and degree of surface porosity on the extent of γ-globulin immobilization was examined. Protein adsorption on these particles was largely related to their surface porosity and pore sizes. The adsorption capacity was established to be greater with mesoporous SFP and SXDP particles at 474 and 377 mg/g, respectively, when compared to significantly low-porosity SAL (16 mg/g). Additionally, γ-globulin immobilization was favored at pH closer to iso-electric point. A key aim of this work was to better understand and improve the limited reversibility of protein adsorption. Protein desorption was found to be lower in simulated intestinal fluid (SIF) in comparison to pH 7.4 phosphate buffer (PB). The use of displacer molecules (sodium dodecyl sulfate [SDS]/Tween 80/Pluronic F127 [PF127]) promoted protein desorption from the adsorbent surface by the exchange mechanism. The PF127 provided substantial release in both studied condition but the highest release of 83% of γ-globulin from SXDP was obtained with tween 80 in PB. The released protein was analyzed with circular dichroism (CD) spectroscopy which indicated that the secondary structure of desorbed γ-globulin was dependent on the pH and displacer molecule. The conformation largely remained unchanged when desorption was carried out in SIF but changed markedly in PB specially in the presence of SDS.

Enhanced pulmonary systemic delivery of protein drugs via zwitterionic polymer conjugation

Pulmonary delivery of protein drugs into the systemic circulation is highly desirable as the lung provides a large absorption surface area and a more favorable environment for biologics compared to other delivery routes. However, pulmonary systemic delivery of proteins presents several challenges such as poor protein stability and limited bioavailability, especially for large proteins (molecular weight > 50 kDa), which exhibit an average bioavailability of 1% to 5% when delivered via the pulmonary route. Here, we demonstrated that with the conjugation of zwitterionic poly(carboxybetaine) (pCB) polymer, the bioavailability of organophosphate hydrolase (OPH) was significantly increased from 5% to 53%. OPH conjugated with pCB delivered through intubation-assisted intratracheal instillation (IAIS) into the lung exhibited improved pharmacokinetic properties and prophylactic efficacy against organophosphate poisoning, showing its application potential. Zwitterionic polymer conjugation provides the possibility for a favorable, non-invasive delivery of biological therapeutics into the systemic circulation.

Establishment and In Vitro Evaluation of Porous Ion-Responsive Targeted Drug Delivery System

Protein drugs have disadvantages, such as short half-lives, unstable biological activities, and low utilization efficiency. In this paper, a porous ion-responsive targeted drug delivery system was designed, combining biodegradable carriers with ion exchange technology to overcome problems for protein drug delivery systems. Carboxymethyl Chitosan Porous Microspheres (CCPM) were prepared using an emulsification- chemical crosslinking method. Chitosan-bovine serum albumin-carboxymethyl chitosan porous microspheres (CBCCPM) were prepared using a dynamic ion exchange method and static self-assembly technology. CCPM were round in appearance mostly with a particle size distribution of 5-15 μm, which facilitates passive targeting to the lungs. CCPM had a total ion exchange capacity of 9.97 ± 0.07 mmol/g and showed a strong ability to attract and contain positively charged drugs. A potentiometric titration curve was used to identify the dissociation behavior of exchangeable groups on the microspheres; the optimal pH for ion exchange of microspheres was ≥ 4.3. CCPM had ion responsiveness, in vitro degradation ability, thermal stability and biocompatibility. In vitro release results confirmed that BSA and CCPM were mainly bound together by ionic bonds and the drug release mechanism of the self-assembled microspheres changed from particle diffusion to membrane diffusion under pH 7.4 PBS solution containing 0.02% Tween 80. Circular dichroism and sodium dodecyl-sulfate polyacrylamide gel electrophoresis results showed no significant change in the secondary structure and purity of BSA after binding to CCPM. The cumulative in vitro release rate of microspheres after 24 h was 86.78%. In this paper, CBCCPM, a porous ion-responsive targeted drug delivery system, was designed.

How the Lack of Chitosan Characterization Precludes Implementation of the Safe-by-Design Concept.

Efficacy and safety of nanomedicines based on polymeric (bio)materials will benefit from a rational implementation of a Safe-by-Design (SbD) approach throughout their development. In order to achieve this goal, however, a standardization of preparation and characterization methods and their accurate reporting is needed. Focusing on the example of chitosan, a biopolymer derived from chitin and frequently used in drug and vaccine delivery vector preparation, this review discusses the challenges still to be met and overcome prior to a successful implementation of the SbD approach to the preparation of chitosan-based protein drug delivery systems.

Recent advances in protein drug delivery

Proteins and peptides drugs have been researched for decades and they show therapeutic and medicative function in numerous aspects. However, how to manipulate proteins efficiently to the specific region of the body or even cellular penetrate are the challenges we face. This overview introduces some potential methods of delivering proteins as well as how they act more accurate and controlled in vivo. Simply classify them to five sections which seem different from each other, whereas have possible connections.

Peptide gels for controlled release of proteins.

Treatment strategies in clinics have been shifting from small molecules to protein drugs due to the promising results of a highly specific mechanism of action and reduced toxicity. Despite their prominent roles in disease treatment, delivery of the protein therapeutics is challenging due to chemical instability, immunogenicity and biological barriers. Peptide hydrogels with spatiotemporally tunable properties have shown an outstanding potential to deliver complex protein therapeutics, maintain drug efficacy and stability over time, mimicking the extracellular matrix, and responding to external stimuli. In this review, we present recent advances in peptide hydrogel design strategies, protein release kinetics and mechanisms for protein drug delivery in cellular engineering, tissue engineering, immunotherapy and disease treatments.

Efficient protein delivery systems based on hierarchical zeolite microspheres constructed by MWW-nanosheets

Abstract A hierarchical hollownest-structured zeolite (HSZ) microsphere constructed by MWW-nanosheets and its various functionalized derivatives (HSZ-OH, HSZ-NH2 and HSZ-CHO) were firstly applied in the delivery of bovine serum albumin (BSA). Owing to the unique cup-shaped pores on the nanosheets and the abundant prismatic stacking mesopores and macropores in the shell, HSZ materials exhibited higher BSA loading content than other familiar microporous zeolites. More importantly, HSZ-NH2 and HSZ-CHO could release exceeded 50% of the loaded BSA under simulated physiological ion strength condition of pH 7.4 and 5.0, respectively. The adsorption thermodynamic parameters revealed that the loading of BSA on HSZ-OH was an enthalpy-driven process conducted by hydrogen bonds, but an entropy-driven process predominated by electrostatic forces on HSZ-NH2. The pH-sensitive imine bonds between BSA and hydrophobic HSZ-CHO were sensitive to acidic environment, constituting a pH-responsive intelligent protein delivery system. The synchronous fluorescence spectra corroborated that structural alteration of BSA recovered after desorption. The interaction mechanisms were analyzed by determining the physicochemical property of nanosheet surface. The favorable and controllable loading and release performance of HSZs predicted their huge application potential in delivery, slow-release, separation and purification of proteins and protein drugs.

Lipid and PLGA Microparticles for Sustained Delivery of Protein and Peptide Drugs.

Solid lipid particles have a great potential in sustained drug delivery, the lipid excipients are solid at room temperature with a slow degradation rate. Poly (D, L-lactic-coglycolic acid) (PLGA) has been successfully clinically applied for the sustained delivery of peptide drugs. A recent study showed the advantage of hybrid PLGA-lipid microparticles (MPs) over PLGA MPs for the sustained delivery of peptide drug in vivo. In this paper, we briefly present PLGA MPs, solid lipid MPs and PLGA lipid hybrid MP prepared by the double emulsion method and the spray drying method and discuss the effects of excipients on encapsulation efficiency of protein and peptide drugs in the MPs. The pros and cons of PLGA MPs, solid lipid MPs and PLGA lipid hybrid MP as carriers for sustained delivery of protein and peptide drugs are also discussed.

Mucoadhesive and pH-responsive behavior of gelatin containing hydrogels for protein drug delivery applications

Novel gelatin-containing polymer hydrogels that can be used as mucoadhesive delivery systems were developed. Poly(acrylic acid) hydrogels were modified by copolymerizing gelatin as adhesion promoter, to improve the adhesion to the mucus layer and the synthesized copolymer of acrylic acid (AA) and methacrylated gelatin (GelMA) were designated as P(AA-co-GelMA). The pH-sensitivity and the mucoadhesive property of the P(AA-co-GelMA) hydrogel were investigated as carries of an oral protein delivery system activated by pH changes of the human GI tract. There was a drastic change in the weight swelling ratio of P(AA-co-GelMA) hydrogels at a pH of around 5, that is, low swelling ratios at a pH below 5, while high swelling ratios at a pH greater than 5. In addition, the swelling ratio increased at a pH above 5, when the AA content in the hydrogel increased. In mucoadhesive experiments using the rheometer, when the GelMA concentration in the P(AA-co-GelMA) hydrogel increased, the maximum force of detachment increased, indicating that the mucoadhesion of the hydrogel was improved. The P(AA-co-GelMA) hydrogels also showed a pH-responsive release behavior. The ratio of the cumulative amounts of Rh-B released from P(AA-co-GelMA) hydrogels at pH 2.6 to pH 7.0 increased, when the AA content in the hydrogel decreased.

Poly(L-Glutamic Acid)-Based Brush Copolymers: Fabrication, Self-assembly, and Evaluation as Efficient Nanocarriers for Cationic Protein Drug Delivery.

Protein drugs were considered to be the first choice to treat many human diseases, but their clinical application was usually limited by their short half-life and lack of validated targeted therapy. Here, a series of folate-functionalized poly(ethylene glycol)-b-(poly(2-aminoethyl-L-glutamate)-g-poly(L-glutamic acid))s (FA-PEG-b-(PELG-g-PLGA)s) were designed as tumor-targeted carriers for cationic protein delivery. Compared with traditional copolymers consisting of PEG and linear charged hydrophilic blocks, FA-PEG-b-(PELG-g-PLGA) with brush-like polyelectrolyte segments were beneficial to improving their electrostatic interactions with loading protein molecules, thus increasing drug-loading stability and protecting encapsulated proteins from degradation. The designed polymer brushes could efficiently encapsulate cytochrome C (CytC), a cationic model protein, to form polyion complex (PIC) micelles with an average particle size of approximately 200nm. An in vitro drug release study showed that the drug-loading stability of the formed PIC micelles was largely improved. The functionalization of the block copolymer carriers with a targeting folate group enhanced the tumor cell growth inhibition and total apoptotic rates induced by CytC. Our results shed light on the unique advantages of brush-like polymer carriers in delivering cationic proteins, and the poly(L-glutamic acid)-based linear-brush diblock copolymers could be applied as a versatile delivery platform for molecular targeting in cancer therapy.

Thermosensitive Hydrogel Based on Poly(2-Ethyl-2-Oxazoline)-Poly(D,L-Lactide)-Poly(2-Ethyl-2-Oxazoline) for Sustained Salmon Calcitonin Delivery.

This study developed a thermosensitive hydrogel based on poly(2-ethyl-2-oxazoline)-poly(D,L-lactide)-poly(2-ethyl-2-oxazoline) (PPP) for the delivery of salmon calcitonin to improve the hypocalcemic effect. The tube inversion and rheological tests revealed that the copolymer solution underwent temperature-dependent sol-gel-sol transitions. Observation by scanning electron microscopy (SEM) showed that the hydrogel exhibited a porous three-dimensional network. The swelling test demonstrated that there was a maximum swelling ratio at low temperature (25°C) as compared with the high temperature (37°C). In vitro release revealed that the PPP hydrogel were capable of sustained release of salmon calcitonin (sCT). The in vivo biodegradability study indicated the good degradability of PPP hydrogel. More importantly, the in vivo retention time of the hydrogel in situ was significantly prolonged after subcutaneous injection of the PPP hydrogel compared to the F127 hydrogel. In vivo pharmacodynamics analysis showed that the hypocalcemic effect of both PPP and F127 hydrogel was significantly greater than that of sCT solution, and the mean serum Ca reduction effect could be maintained for 24h of PPP hydrogel, indicating that PPP hydrogel could achieve a significant enhanced hypocalcemic effect. In conclusion, the PPP hydrogel has been shown to be prospective as a controlled release carrier for injection delivery of protein drugs.

Design of new protein drug delivery system (PDDS) with photoactive compounds as a potential application in the treatment of glioblastoma brain cancer.

Glioblastoma multiforme (GBM) is an extremely aggressive malignant brain tumor. Despite advances in treatment modalities, it remains largely incurable. This unfavorable prognosis for GBM is at least partly due to the lack of a successful drug delivery system across the blood-brain barrier (BBB). The delivery of drugs through nanomedicines combined with less invasive alternative therapies represents an important hope for the future of these incurable brain tumors. Whey protein nanocarriers represent promising strategy for targeted drug delivery to tumor cells by enhancing the drug's bioavailability and distribution, and reducing the body's response towards drug resistance. They have been extensively studied to find new alternatives for capacity to encapsulate different drugs and no need for cross-linkers. In this study, we report for the first time the incorporation and administration of Aluminum phthalocyanine chloride (AlClPc)-loaded whey protein drug delivery system (AlClPc-PDDS) for the treatment of glioblastoma brain cancer. This system was designed and optimized (with the use of the spray drying technique) to obtain the required particle size (in the range of 100 to 300nm), zeta potential and drug loading. Our results suggest that we have developed a drug delivery system from a low-cost raw material and preparation method that is capable of incorporating hydrophobic drugs which, in combination with irradiation, cause photodamage to neoplasic cells, working as an effective adjuvant treatment for malignant glioma.

Multiple targeting strategies achieve novel protein drug delivery into proapoptosis lung cancer cells by precisely inhibiting survivin.

Therapeutic recombinant proteins have numerous advantages and benefits over chemical drugs, particularly high specificity and good biocompatibility. However, the therapeutic potential and clinical application of current anticancer protein drugs are limited as most biomarkers are located within cells, and multiple physiological barriers exist between the point of administration and the intracellular biomarker. Herein, we report a novel strategy to accurately deliver a cell-permeable dominant-negative TATm-Survivin (TmSm) protein (T34A) to intracellular survivin in cancer cells by overcoming multiple barriers in vivo. A poly(d,l-lactide-co-glycolide) (PLGA) inner core, a polyethylene glycol (PEG) modification, and a TATm peptide were simultaneously introduced to mediate tumor tissue targeting and response to pH-triggered TmSm release. Compared to free TmSm, the PEGylated-PLGA nanoparticle platform achieved a significantly higher cellular uptake efficiency (1.79-fold for A549 and 1.77-fold for Capan-2), effectively decreased IC50 (1.22-fold for A549 and 1.17-fold for Capan-2), and largely elevated apoptosis in different cancer cells (1.17-fold for A549 and 1.15-fold for Capan-2). Besides, this newly developed nanoplatform showed increased protein drug accumulation in the tumor site in A549-bearing nude mice and reached a tumor inhibition rate of 55.81% (1.35-fold versus free TmSm) by reducing the expression of intracellular survivin. All these results confirmed that our newly developed delivery strategy is a very promising tool, which helps protein drugs to cross multiple barriers in vivo and achieves precise targeting to intracellular biomarkers. This strategy could also be applied to other types of protein drugs to further improve their clinical anticancer therapeutic efficacy.

BIOAVAILABILITY ENHANCEMENT AND LIPID NANOCARRIER BASED DELIVERY OF PEPTIDES AND PROTEINS

Peptides and proteins are vital biomacromolecules that perform several bodily functions in various physiological and biological processes. Being biocompatible and biodegradable, these macromolecules are considered promising platforms for delivery of drugs and genes. However, peptides and proteins suffer from major limitations including enzymatic degradation, short circulation half-lives, and poor membrane permeability that leads to poor bioavailability, challenging their effective delivery. This article briefly discusses the inherent challenges in peptide and protein delivery along with strategies for bioavailability enhancement and lipid nanocarriers as prospective systems for peptide and protein drug delivery.

Advances in colon-targeted nano-drug delivery systems: challenges and solutions.

Nano-drug delivery systems (NDDS) for colon-targeted drug delivery are an active area of research on local diseases affecting the colon, such as ulcerative colitis, Crohn's disease, colon cancer, and for the delivery of peptide or protein drugs and vaccinations. In particular, targeted nano-drug delivery to the colon is advantageous for colon-specific diseases because nanoparticles can accumulate in diseased parts, improve the efficacies of therapeutics, and enable localized treatments, which reduces systemic toxicity. However, there are many hurdles, such as burst drug release, enzyme and acidic degradation of drug and carrier in the stomach, pH variations, mucus entrapment, and systemic uptake in the upper small intestine, which could challenge and compromise the successful delivery of NDDS to the colon. With advancements in NDDS, it may be possible to overcome these challenges leading to efficient drug delivery for colon-specific disorders. This review describes a few of the potential colon-specific drug delivery areas and the challenges faced by colon-targeted orally administered delivery systems, and provides an updated summary of recent advances in the development of orally administered NDDS for colon targeting, and the future advances in this research.

Recent Advances in Protein and Peptide Drug Delivery

Peptides and proteins have great therapeutic potential. Proteins and peptides may be administered for therapeutic effects at comparatively low doses because of their relatively specific mode of action. For several chronic conditions such as cancer, hepatitis, diabetes, rheumatoid arthritis and leukaemia, this potent therapy is indicated. While the peptide and protein therapeutic market has developed significantly over the past decades, their use has been limited by delivery. Most are currently delivered intravenously or subcutaneously due to degradation and limited absorption in the gastrointestinal tract, although oral delivery is preferred. In order to facilitate the oral peptide delivery, absorption enhancers, enzyme inhibitors, carrier systems and stability enhancers are therefore being studied. Additionally, the delivery of transdermal peptides avoids gastrointestinal tract problems but also faces absorption limitations. Injections (i.e. intravenous, intramuscular, or subcutaneous route) remain the most common means of administering these protein and peptide drugs until recently. The oral, buccal, intranasal, pulmonary, transdermal, ocular and rectal routes that have been tried with varying degrees of success. This review discusses oral and transdermal peptide drug delivery, focusing on barriers and solutions to absorption and recent advances are discussed.