Significance and strategies in developing delivery systems for bio-macromolecular drugs

Metal-organic frameworks (MOFs) as host materials for the enhanced delivery of biomacromolecular therapeutics

Biomacromolecular drugs have become an important class of therapeutic agents for the treatment of human diseases. Considering their high propensity for being degraded in the human body, the choice of an appropriate delivery system is key to ensure the therapeutic efficacy of biomacromolecular drugs in vivo. As an emerging class of supramolecular "host" materials, metal-organic frameworks (MOFs) exhibit advantages in terms of the tunability of pore size, encapsulation efficiency, controllable drug release, simplicity in surface functionalization and good biocompatibility. As a result, MOF-based host-guest systems have been extensively developed as a new class of flexible and powerful platform for the delivery of therapeutic biomacromolecules. In this review, we summarize current research progress in the synthesis of MOFs as delivery materials for a variety of biomacromolecules. Firstly, we briefly introduce the advances made in the use of biomacromolecular drugs for disease therapy and the types of commonly used clinical delivery systems. We then describe the advantages of using MOFs as delivery materials. Secondly, the strategies for the construction of MOF-encapsulated biomacromolecules (Biomacromolecules@MOFs) and the release mechanisms of the therapeutics are categorized. Thirdly, the application of MOFs to deliver different types of biomacromolecules (e.g., antigens/antibodies, enzymes, therapeutic proteins, DNA/RNA, polypeptides, and polysaccharides) for the treatment of various human diseases based on immunotherapy, gene therapy, starvation therapy and oxidation therapy is summarized. Finally, the remaining challenges and available opportunities for MOFs as drug delivery systems are outlined, which we anticipate will encourage additional research efforts directed towards developing Biomacromolecules@MOFs systems for biomedical applications.

Shotgun Proteomics and Mass Spectrometry as a Tool for Protein Identification and Profiling of Bio-Carrier-Based Therapeutics on Human Cancer Cells

Shotgun proteomics has been widely applied to study proteins in complex biological samples. Combination of high-performance liquid chromatography with mass spectrometry has allowed for comprehensive protein analysis with high resolution, sensitivity, and mass accuracy. Prior to mass spectrometry analysis, proteins are extracted from biological samples and subjected to in-solution trypsin digestion. The digested proteins are subjected for clean-up and injected into the liquid chromatography-mass spectrometry system for peptide mass identification. Protein identification is performed by analyzing the mass spectrometry data on a protein search engine software such as PEAKS studio loaded with protein database for the species of interest. Results such as protein score, protein coverage, number of peptides, and unique peptides identified will be obtained and can be used to determine proteins identified with high confidence. This method can be applied to understand the proteomic changes or profile brought by bio-carrier-based therapeutics in vitro. In this chapter, we describe methods in which proteins can be extracted for proteomic analysis using a shotgun approach. The chapter outlines important in vitro techniques and data analysis that can be applied to investigate the proteome dynamics.

A Guided Walk through the World of Mesoporous Bioactive Glasses (MBGs): Fundamentals, Processing, and Applications

Bioactive glasses (BGs) are traditionally known to be able to bond to living bone and stimulate bone regeneration. The production of such materials in a mesoporous form allowed scientists to dramatically expand the versatility of oxide-based glass systems as well as their applications in biomedicine. These nanostructured materials, called mesoporous bioactive glasses (MBGs), not only exhibit an ultrafast mineralization rate but can be used as vehicles for the sustained delivery of drugs, which are hosted inside the mesopores, and therapeutic ions, which are released during material dissolution in contact with biological fluids. This review paper summarizes the main strategies for the preparation of MBGs, as well as their properties and applications in the biomedical field, with an emphasis on the methodological aspects and the promise of hierarchical systems with multiscale porosity.

Naturally derived nano- and micro-drug delivery vehicles: halloysite, vaterite and nanocellulose

We discuss prospects for halloysite nanotubes, vaterite crystals and nanocellulose to enter the market of biomaterials for drug delivery and tissue engineering, and their potential for economically viable production from abundant natural sources.

CPP-Assisted Intracellular Drug Delivery, What Is Next?

For the past 20 years, we have witnessed an unprecedented and, indeed, rather miraculous event of how cell-penetrating peptides (CPPs), the naturally originated penetrating enhancers, help overcome the membrane barrier that has hindered the access of bio-macromolecular compounds such as genes and proteins into cells, thereby denying their clinical potential to become potent anti-cancer drugs. By taking the advantage of the unique cell-translocation property of these short peptides, various payloads of proteins, nucleic acids, or even nanoparticle-based carriers were delivered into all cell types with unparalleled efficiency. However, non-specific CPP-mediated cell penetration into normal tissues can lead to widespread organ distribution of the payloads, thereby reducing the therapeutic efficacy of the drug and at the same time increasing the drug-induced toxic effects. In view of these challenges, we present herein a review of the new designs of CPP-linked vehicles and strategies to achieve highly effective yet less toxic chemotherapy in combating tumor oncology.

Engineering Intrinsically Zirconium-89 Radiolabeled Self-Destructing Mesoporous Silica Nanostructures for In Vivo Biodistribution and Tumor Targeting Studies

A systematic study of in vitro and in vivo behavior of biodegradable mesoporous silica nanoparticles (bMSNs), designed to carry multiple cargos (both small and macromolecular drugs) and subsequently self-destruct following release of their payloads, is presented. Complete degradation of bMSNs is seen within 21 d of incubation in simulated body fluid. The as-synthesized bMSNs are intrinsically radiolabeled with oxophilic zirconium-89 (89Zr, t1/2 = 78.4 h) radionuclide to track their in vivo pharmacokinetics via positron emission tomography imaging. Rapid and persistent CD105 specific tumor vasculature targeting is successfully demonstrated in murine model of metastatic breast cancer by using TRC105 (an anti-CD105 antibody)-conjugated bMSNs. This study serves to illustrate a simple, versatile, and readily tunable approach to potentially overcome the current challenges facing nanomedicine and further the goals of personalized nanotheranostics.

Modeling nanoparticle delivery of TB drugs to granulomas

Tuberculosis, which typically presents as a pulmonary disease, has a complex pathology. The primary site of infection, the Ghon focus, recruits immune cells and a granuloma forms. At earlier stages the granuloma is still vascularized, offering the best opportunity for drug treatment. In the more progressive state blood flow is reduced and a distinct caseous structure develops. Effective delivery of drugs to bacilli in the core of the granuloma becomes very difficult. It is perceivable that granuloma cores could create conditions where bacilli persist and develop resistance. In this study we analyze drug delivery to granulomas by means of a nanoparticle delivery system. The model consists of two parts; the overall distribution of the nanoparticles is described by a simple circulatory model and this result is used in the second part, focusing on transport in a capillary lined with macrophages. Nanoparticles enter the macrophages where they are metabolized and the drugs are released. The model reveals significant differences in drug concentrations between the plasma and macrophages. Based on the results of the model, strategies for improved drug delivery are proposed.

Surface modification and endothelialization of biomaterials as potential scaffolds for vascular tissue engineering applications

This review highlights the recent developments of surface modification and endothelialization of biomaterials in vascular tissue engineering applications.

15 years of ATTEMPTS: a macromolecular drug delivery system based on the CPP-mediated intracellular drug delivery and antibody targeting

Traditionally, any drug intended for combating the tumor would distribute profoundly to other organs and tissues as lack of targeting specificity, thus resulting in limited therapeutic effects toward the tumor but severe drug-induced toxic side effects. To prevail over this obstacle of drug-induced systemic toxicity, a novel approach termed "ATTEMPTS" (antibody targeted triggered electrically modified prodrug type strategy) was designed, which directly introduces both of the targeting and prodrug features onto the protein drugs. The ATTEMPTS system is composed of the antibody targeting component consisting of antibodies linked with heparin, and the cell penetrating peptide (CPP) modified drug component. The two components mentioned above self-assembled into a tight complex via the charge to charge interaction between the anionic heparin and cationic CPP. Once accumulated at the targeting site, the CPP modified drug is released from the blockage by a second triggering agent, while remaining inactive in the circulation during tumor targeting thus aborting its effect on normal tissues. We utilized the heparin-induced inhibition on the cell-penetrating activity of CPP to create the prodrug feature, and subsequently the protamine-induced reversal of heparin inhibition to resume cell transduction of the protein drug via the CPP function. Our approach is the first known system to overcome this selectivity issue, enabling CPP-mediated cellular drug delivery to be practically applicable clinically. In this review, we thoroughly discussed the historical and novel progress of the "ATTEMPTS" system.