DNA Strands Trigger the Intracellular Release of Drugs from Mucin-Based Nanocarriers

Nucleic acid-responsive smart systems for controlled cargo delivery

Stimulus-responsive delivery systems allow controlled, highly regulated, and efficient delivery of various cargos while minimizing side effects. Owing to the unique properties of nucleic acids, including the ability to adopt complex structures by base pairing, their easy synthesis, high specificity, shape memory, and configurability, they have been employed in autonomous molecular motors, logic circuits, reconfigurable nanoplatforms, and catalytic amplifiers. Moreover, the development of nucleic acid (NA)-responsive intelligent delivery vehicles is a rapidly growing field. These vehicles have attracted much attention in recent years due to their programmable, controllable, and reversible properties. In this work, we review several types of NA-responsive controlled delivery vehicles based on locks and keys, including DNA/RNA-responsive, aptamer-responsive, and CRISPR-responsive, and summarize their advantages and limitations.

DNA Crosslinked Mucin Hydrogels Allow for On-Demand Gel Disintegration and Triggered Particle Release

Whereas hydrogels created from synthetic polymers offer a high level of control over their stability and mechanical properties, their biomedical activity is typically limited. In contrast, biopolymers have evolved over billions of years to integrate a broad range of functionalities into a single design. Thus, biopolymeric hydrogels can show remarkable capabilities such as regulatory behavior, selective barrier properties, or antimicrobial effects. Still, despite their widespread use in numerous biomedical applications, achieving a meticulous control over the physical properties of macroscopic biopolymeric networks remains a challenge. Here, a macroscopic, DNA-crosslinked mucin hydrogel with tunable viscoelastic properties that responds to two types of triggers: temperature alterations and DNA displacement strands, is presented. As confirmed with bulk rheology and single particle tracking, the hybridized base pairs governing the stability of the hydrogel can be opened, thus allowing for a precise control over the hydrogel stiffness and even enabling a full gel-to-sol transition. As those DNA-crosslinked mucin hydrogels possess tunable mechanical properties and can be disintegrated on demand, they can not only be considered for controlled cargo release but may also serve as a role model for the development of smart biomedical materials in applications such as tissue engineering and wound healing.

Fabrication and Characterization of Mucin Nanoparticles for Drug Delivery Applications

Mucin glycoproteins are ideal biomacromolecules for drug delivery applications since they naturally offer a plethora of different functional groups that can engage in specific and unspecific binding interactions with cargo molecules. However, to fabricate drug carrier objects from mucins, suitable stabilization mechanisms have to be implemented into the nanoparticle preparation procedure that allow for drug release profiles that match the requirements of the selected cargo molecule and its particular mode of action. Here, we describe two different methods to prepare crosslinked mucin nanoparticles that can release their cargo either on-demand or in a sustained manner. This method chapter includes a description of the preparation and characterization of mucin nanoparticles (stabilized either with synthetic DNA strands or with covalent crosslinks generated by free radical polymerization), as well as protocols to quantify the release of a model drug from those nanoparticles.

Enhancing biofilm penetration and antibiofilm efficacy with protein nanocarriers against pathogenic biofilms

Nanocarriers play an important role in enhancing the efficacy of antibiotics against biofilms by improving their penetration and prolonging retention in pathogenic biofilms. Herein, the multifunctional nanocarriers including nanospheres (NS) and nanotubes (NT) with a high biocompatibility and biodegradability were prepared through self-assembly of partially hydrolyzed α-lactalbumin. The effects of these two different shaped nanocarriers on the delivery of antibiotics for biofilm treatment were examined by conducting in vitro antibiofilm experiment and in vivo infected wound model. The strong affinity of NS and NT for the bacterial surface allows antibiotics to be concentrated in the bacteria. Notably, the high permeability of NT into biofilms facilitates deeper penetration and the easier diffusion of loaded antibiotics within the biofilm. Furthermore, the acidic biofilm environment triggers the release of antibiotics from the NT, resulting in the accumulation of high local antibiotic concentrations. Therefore, NT could efficiently clean and inhibit the biofilm formation while also destroying the mature biofilms. In a S. aureus infected wound animal model, treatment with antibiotic-loaded NT demonstrated accelerated healing of S. aureus infected wounds when compared to free antibiotic treatment. These findings indicate that NT nanocarrier strategy is promising for treating bacterial biofilm infections, offering the potential for lower antibiotics dosages and preventing the overuse of antibiotics.

Crystallinity-tuned ultrasoft polymeric DNA networks for controlled release of anticancer drugs

Despite the vast interest in utilizing rolling circle amplification (RCA)-based DNA networks for bioapplications, precise control of the mechanical and physicochemical properties is highly challenging. To address this concern, we aimed to develop ultrasoft self-supporting polymerized DNA networks (pDNets) of variable crystallinities to manipulate sequence-mediated drug release efficiency. A controlled ratio of the inorganic magnesium pyrophosphate (MgPPi) crystal to the organic polymeric DNA resulted in the synthesis of pDNets of various nanoporosities. The number of crystal microstructures influencing drug localization and release pattern and the tunable mechanical properties influencing injectability and structural stability under physiological conditions were investigated. The pDNets exhibited ultrasoft properties with Young's moduli of 0.06-0.54 Pa; approximately 9-fold differences in mechanical properties were obtained by varying the degree of crystallinity. With functional DNA sequences, the developed platforms showed pH stimuli-responsive drug release profiles of the dynamic DNA structures and aptamer-specific cell target adhesion efficiency. Analyses of controlled delivery of anticancer therapeutics in vitro and in vivo revealed crystallinity-dependent antitumor efficacy without side effects. This strategy provides an effective one-pot enzymatic polymerization methodology and a favorable microenvironment for a three-dimensional DNA network based on demand-localized drug delivery.

Recombinant mucin biotechnology and engineering

Mucins represent a largely untapped class of polymeric building block for biomaterials, therapeutics, and other biotechnology. Because the mucin polymer backbone is genetically encoded, sequence-specific mucins with defined physical and biochemical properties can be fabricated using recombinant technologies. The pendent O-glycans of mucins are increasingly implicated in immunomodulation, suppression of pathogen virulence, and other biochemical activities. Recent advances in engineered cell production systems are enabling the scalable synthesis of recombinant mucins with precisely tuned glycan side chains, offering exciting possibilities to tune the biological functionality of mucin-based products. New metabolic and chemoenzymatic strategies enable further tuning and functionalization of mucin O-glycans, opening new possibilities to expand the chemical diversity and functionality of mucin building blocks. In this review, we discuss these advances, and the opportunities for engineered mucins in biomedical applications ranging from in vitro models to therapeutics.

Engineering poly- and micelleplexes for nucleic acid delivery - A reflection on their endosomal escape

For the longest time, the field of nucleic acid delivery has remained skeptical whether or not polycationic drug carrier systems would ever make it into clinical practice. Yet, with the disclosure of patents on polyethyleneimine-based RNA carriers through leading companies in the field of nucleic acid therapeutics such as BioNTech SE and the progress in clinical studies beyond phase I trials, this aloofness seems to regress. As one of the most striking characteristics of polymer-based vectors, the extraordinary tunability can be both a blessing and a curse. Yet, knowing about the adjustment screws and how they impact the performance of the drug carrier provides the formulation scientist committed to its development with a head start. Here, we equip the reader with a toolbox - a toolbox that should advise and support the developer to conceptualize a cutting-edge poly- or micelleplex system for the delivery of therapeutic nucleic acids; to be specific, to engineer the vector towards maximum endosomal escape performance at minimum toxicity. Therefore, after briefly sketching the boundary conditions of polymeric vector design, we will dive into the topic of endosomal trafficking. We will not only discuss the most recent knowledge of the endo-lysosomal compartment but further depict different hypotheses and mechanisms that facilitate the endosomal escape of polyplex systems. Finally, we will combine the different facets introduced in the previous chapters with the fundamental building blocks of polymer vector design and evaluate the advantages and drawbacks. Throughout the article, a particular focus will be placed on cellular peculiarities, not only as an additional barrier, but also to give inspiration to how such cell-specific traits might be capitalized on.

Recent Advancements in the Design of Nanodelivery Systems of siRNA for Cancer Therapy

RNA interference (RNAi) has increased the possibility of restoring RNA drug targets for cancer treatment. Small interfering RNA (siRNA) is a promising therapeutic RNAi tool that targets the defective gene by inhibiting its mRNA expression and stopping its translation. However, siRNAs have flaws like poor intracellular trafficking, RNase degradation, rapid kidney filtration, off-targeting, and toxicity, which limit their therapeutic efficiency. Nanocarriers (NCs) have been designed to overcome such flaws and increase antitumor activity. Combining siRNA and anticancer drugs can give synergistic effects in cancer cells, making them a significant gene-modification tool in cancer therapy. Our discussion of NCs-mediated siRNA delivery in this review includes their mechanism, limitations, and advantages in comparison with naked siRNA delivery. We will also discuss organic NCs (polymers and lipids) and inorganic NCs (quantum dots, carbon nanotubes, and gold) that have been reported for extensive delivery of therapeutic siRNA to tumor sites. Finally, we will conclude by discussing the studies based on organic and inorganic NCs-mediated siRNA drug delivery systems conducted in the years 2020 and 2021.

A pH-stable, mucin based nanoparticle system for the co-delivery of hydrophobic and hydrophilic drugs

Biopolymer-based drug carriers are commonly used for the development of safe delivery systems. However, biopolymer-based systems are often highly sensitive to the acidic pH levels in the stomach and release most of their cargo before they have reached their point of destination. Such premature drug release combined with the resulting high dose requirements is not cost-efficient and comes with the risk of unwanted side effects on non-target tissues/organs. This problem can be mitigated by the mucin-based drug carriers developed here, which exhibit good stability at acidic pH levels as proven by dynamic light scattering and enzymatic degradation tests with pepsin. In addition, the mucin-based particles can deliver hydrophobic and hydrophilic drugs simultaneously, which is demonstrated both with experiments performed under in vitro sink conditions and with drug transport tests involving eukaryotic cells as targets. As photo-induced cross-links covalently stabilize those particles, they can release their payload over time in a sustained manner. The drug carrier system introduced here combines good stability with high drug encapsulation efficiency and very good biocompatibility and thus may be valuable for a broad spectrum of applications in biological settings.

Protein Nanoparticles: Uniting the Power of Proteins with Engineering Design Approaches

Protein nanoparticles, PNPs, have played a long-standing role in food and industrial applications. More recently, their potential in nanomedicine has been more widely pursued. This review summarizes recent trends related to the preparation, application, and chemical construction of nanoparticles that use proteins as major building blocks. A particular focus has been given to emerging trends related to applications in nanomedicine, an area of research where PNPs are poised for major breakthroughs as drug delivery carriers, particle-based therapeutics or for non-viral gene therapy.

Covalently Crosslinked Pig Gastric Mucin Hydrogels Prepared by Radical-based Chain-Growth and Thiol-ene Mechanisms

Mucin, a high molecular mass hydrophilic glycoprotein, is the main component of mucus that coats every wet epithelium in animals. It is thus intrinsically biocompatible, and with its protein backbone and the o-glycosidic bound oligosaccharides, it contains a plethora of functional groups which can be used for further chemical modifications. In this study we introduce and compare chain-growth and step-growth (thiol-ene) free-radical crosslinked hydrogels prepared from commercially available pig gastric mucin (PGM) as cost-efficient and easily accessible alternative to the more broadly applied bovine submaxillary gland mucin (BSM). For this, PGM was functionalized with photoreactive acrylate groups or allylether-moieties, respectively. Whereas homopolymerization of acrylate functionalized polymers was performed, for thiol-ene crosslinking, the allylether functionalized PGM was cross-linked with thiol-functionalized hyaluronic acid (HA). Morphology, mechanical properties, and cell compatibility of both kinds of PGM hydrogels are characterized and compared. Furthermore, the biocompatibility of these hydrogels could be evaluated in cell culture experiments. This article is protected by copyright. All rights reserved.

A tyrosinase-responsive tumor-specific cascade amplification drug release system for melanoma therapy

Tumor-selective drug delivery could enhance anticancer efficacy and avoid drug side effects. However, because of tumor heterogeneity, current nanoparticle-based drug delivery systems rarely improve clinical outcomes significantly, commonly only reducing systemic toxicity. In this work, a new tumor-specific, tyrosinase-responsive cascade amplification release nanoparticle (TR-CARN) was developed to fulfill the needs for tumor-specific drug delivery and high efficacy cancer treatment. Tyrosinase (Tyr) is specifically expressed in melanomas and can catalyze acetaminophen (APAP) to increase reactive oxygen species (ROS). It was therefore utilized here to initiate the ROS amplification procedure. In TR-CARN, a ROS-responsive prodrug BDOX was loaded into an amphiphilic polymer, and APAP was linked to the polymer through a ROS-cleavable thioether bond. TR-CARN caused reduced side effects during the delivery because of the low toxicity of BDOX. Once TR-CARN entered into the tumor, endogenous ROS triggered initial APAP and BDOX release. Tyr-mediated ROS synthesis by APAP then accelerated APAP and BDOX release and toxification. Consequently, TR-CARN achieved melanoma-specific treatment of high efficacy through the cascade amplification strategy with enhanced biosafety.

Emulsions of hydrolyzable oils for the zero-order release of hydrophobic drugs

Drug delivery systems that release hydrophobic drugs with zero-order kinetics remain rare and are often complicated to use. In this work, we present a gellified emulsion (emulgel) that comprises oil droplets of a hydrolyzable oil entrapped in a hydrogel. In the oil, we incorporate various hydrophobic drugs and, because the oil hydrolyzes with zero-order kinetics, the release of the drugs is also linear. We tune the release period from three hours to 50 h by varying the initial oil concentration. We show that the release rate is tunable by varying the initial drug concentration. Our quantitative understanding of the system allows for predicting the drug release kinetics once the drug's partition coefficient between the oil and the aqueous phase is known. Finally, we show that our drug delivery system is fully functional after storing it at -20 °C. Cell viability studies show that the hydrolyzable oil and its hydrolysis product are non-toxic under the employed conditions. With its simplicity and versatility, our system is a promising platform for the zero-order release of the drug.

DNA-Assisted Smart Nanocarriers: Progress, Challenges, and Opportunities

Due to powerful breakthroughs in nanotechnology, smart delivery mechanisms have rapidly emerged for use in diverse applications across biomedical research and therapeutic development. Recent efforts toward understanding stimuli-responsive strategies have led to substantial improvements in their conceptual application and in vitro efficiency. Because disease targets for therapy are often localized in specific cells, organs, or tissues, an enhanced permeability and retention (EPR)-based strategy remains inadequate for accurate drug delivery and release to target regions, resulting in an insufficient drug concentration reaching the target region and undesired side effects. To address these issues, more precise and remote-controlled stimuli-responsive systems, which recognize and react to changes in the pathophysiological microenvironment, were recently elucidated as feasible on-demand drug-delivery systems. In this Perspective, we focus on progress toward stimuli-responsive drug-delivery systems that utilize dynamic DNA molecules by exploiting DNA nanotechnology. DNA structures can be precisely reconfigured by external and internal stimuli to drive the release of a loaded drug in a target region with appropriate microenvironments. We describe the chemical, physical, and biological engineering principles and strategies for constructing DNA-assisted nanocarriers. We also provide a summary of smart nanocarrier systems, organized with respect to the structural changes in the DNA strand in the microenvironment, resulting from changes in pH and temperature and the presence of intracellular oligonucleotides. To do so, we highlight recent advances in related biomedical research and applications as well as discuss major challenges and opportunities for DNA-assisted nanocarriers to guide the development of future in vivo therapies and clinical translation strategies.