Emerging delivery systems based on aqueous two-phase systems: A review

Aqueous two-phase systems: Methods of binodal curve generation and applications

Aqueous two-phase system (ATPS) has been of interest to both industry and academia for the extraction and purification of biomolecules/bioactives. ATPSs are formed by two-phase forming components such as polymer-polymer, polymer-salt, surfactant-salt, etc. when dissolved in water above critical concentrations. The binodal curve distinguishes the single-phase region from the two-phase region. These compositions are usually expressed in weight or mole fractions. The binodal curve and tie-lines in the phase diagram are pivotal in the design of extraction experiments, phase separation, and determining the concentration of phase-forming components. An engineered choice of working on a tie-line determines the purity and yield of the extracted compound. Researchers have explored various approaches for the generation of binodal curves including, macroscale, microscale, thermodynamic, and computational methods. Although different methods have been used for the generation of the binodal curves, there is limited information that summarizes these methods comprehensively. This article aims to summarize the different techniques of binodal curve generation for ATPSs, outlining their merits and demerits, along with the applications of ATPSs. Comparison of different methods for the generation of binodal curves is slightly challenging as every method is distinct and unique. In the case of the convenient method, the macroscale approach could be the preferred one, whereas the microscale approach is advantageous for the rapid generation with low volumes of samples. Furthermore, thermodynamic modeling and computational approaches can be preferred for the generation of binodal curves when minimizing experimentation and sophisticated equipment is a priority.

Ultra-small starch microspheres with narrow size distribution prepared in aqueous two-phase system of starch-PVP

It is challenging to fabricate uniform starch microspheres (SMs) with sub-10 μm diameters in starch-polyethylene glycol (PEG) aqueous two-phase system (ATPS). To address this issue, a refined approach using starch-polyvinylpyrrolidone (PVP) ATPS is presented in this work. Phase diagrams were constructed for ATPSs containing PVPs of varying molecular weights, which provided crucial insights into the influence of PVP on SM formation. The results revealed that increasing both the molecular weight and concentration of PVP led to higher starch and PVP contents within the dispersed phase, significantly influencing the final yield of SMs. The morphology, size, crystallinity, and swelling behavior of SMs prepared in the starch-PVP ATPS were comprehensively characterized. Increasing PVP molecular weight resulted in smaller SMs with enhanced crystallinity and reduced swelling capacity. Notably, SMs prepared with 58 kDa PVP exhibited an average particle size (D[4,3) of 5.13 μm, a narrow size distribution (Span value = 1.33), a B + V crystal type, and a relative crystallinity of 20.9 %. Furthermore, no residual PVP was detected in the final SMs. This innovative starch-PVP ATPS approach offers a promising route for the controlled fabrication of sub-10 μm SMs with tightly controlled size distributions. This method holds significant potential for applications demanding well-defined starch-based materials in various fields. This innovative starch-PVP ATPS approach offers a promising route for controlled fabrication of uniform SMs with sub-10 μm diameters, which could be advantageous for drug encapsulation and delivery systems requiring high structural stability.

Nanomaterials-Based Drug Delivery Systems for Therapeutic Applications in Osteoporosis

The etiology of osteoporosis is rooted in the disruption of the intricate equilibrium between bone formation and bone resorption processes. Nevertheless, the conventional anti-osteoporotic medications and hormonal therapeutic regimens currently employed in clinical practice are associated with a multitude of adverse effects, thereby constraining their overall therapeutic efficacy and potential. Recently, nanomaterials have emerged as a promising alternative due to their minimal side effects, efficient drug delivery, and ability to enhance bone formation, aiding in restoring bone balance. This review delves into the fundamental principles of bone remodeling and the bone microenvironment, as well as current clinical treatment approaches for osteoporosis. It subsequently explores the research status of nanomaterial-based drug delivery systems for osteoporosis treatment, encompassing inorganic nanomaterials, organic nanomaterials, cell-mimicking carriers and exosomes mimics and emerging therapies targeting the osteoporosis microenvironment. Finally, the review discusses the potential of nanomedicine in treating osteoporosis and outlines the future trajectory of this burgeoning field. The aim is to provide a comprehensive reference for the application of nanomaterial-based drug delivery strategies in osteoporosis therapy, thereby fostering further advancements and innovations in this critical area of medical research.

Highly Stable, Excellent Foliar Adhesion and Anti-Photodegradation Nucleic Acid-Peptide Coacervates for Broad Agrochemicals Delivery

Agrochemicals play a pivotal role in the management of pests and diseases and the way agrochemicals are utilized exerts significant impacts on the environment. Ensuring rational application and improving utilization rates of agrochemicals are major demands in developing green delivery systems. Herein, a model of nucleic acid-peptide coacervate (NPC) for agrochemical delivery is presented, which is formed by mixing negatively charged single-stranded DNAs with positively charged poly-L-lysine. The NPC microsystem exhibits broad loading capacities for various types of agrochemicals. Furthermore, the NPCs demonstrate remarkable protection against photodegradation for photosensitive agrochemicals. In the foliar interactions, the NPCs exhibit excellent wetting performances and foliar adhesion on hydrophobic cabbage leaves and wheat leaves infected with powdery mildew to facilitate direct spaying in practical applications. Subsequently, the NPC microsystem is stabilized against coalescence by a charged comb polymer. Then, the NPC loaded with emamectin benzoates (EBs) exhibited significantly higher insecticidal activity compared to free EBs. This enhanced efficacy can be attributed to the higher insect uptake efficiency of the NPC formulation, as evidenced by fluorescent imaging of mosquito larvae. This coacervate model provides a new biocompatible and highly efficient system for future agrochemical delivery that actively contributes to eco-friendly and sustainable agriculture.

Processable and controllable all-aqueous gels based on high internal phase water-in-water emulsions

Aqueous two-phase systems (ATPSs) have primarily been developed in the form of emulsions to enhance their utilization in green and biocompatible applications. However, numerous challenges have arisen in forming stable and processable water-in-water (W/W) emulsion systems, as well as in fine-tuning the interconnectivity of their internal structure, which can significantly impact their performance. To effectively address these challenges, we elucidate, for the first time, the root cause of the poor stability of W/W emulsions. Leveraging this insight, we successfully stabilize W/W high internal phase emulsions (W/W HIPEs) characterized by an extremely thin continuous phase. This stabilization enables the fine-tuning of interconnectivity between dispersed droplets through photopolymerization of thin continuous phases, resulting in the fabrication of stable and processable all-aqueous gels. This W/W HIPE-based gel fabrication holds promise as a universal technology for a wide range of applications. It facilitates in situ polymerization of the continuous phase of W/W HIPEs, where target molecules are stored in the dispersed phase. Moreover, this method allows easy adjustment of the external release rate or internal transfer rate of target molecules by adjusting the interconnectivity of the internal structures.

Phase equilibria and drug partitioning ability of betaine based aqueous two-phase systems

The aqueous two-phase system (ATPS) as an environmentally friendly technique has a high potential for extraction of drugs, proteins, metals, etc. In this work first the formation of ATPSs by betaine, which is a novel, low toxic, and high biodegradable material, and polyethylene glycol or phosphate salts (K3PO4 and K2HPO4) were investigated temperatures of 298.15, 308.15, 318.15 K and atmospheric pressure (≈ 85 kPa). The effect of increasing temperature on the binodal curves was investigated. The experimental binodal data were correlated using two empirical nonlinear three parameter expressions developed by Merchuk, and Zafarani-Moattar et al. and the two-parameter modified equation derived from effective excluded volume theory. Then, the experimental tie-line data were represented with Othmer-Tobias and Setschenow correlations. Finally, in these ATPSs the partition behavior of analgesic drugs, namely acetaminophen, salicylic acid, and ceftriaxone were investigated by measuring of partition coefficient and extraction efficiency. The trend of obtained results showed that the selected drugs were successfully extracted into the top phase of studied ATPSs with a partition coefficient greater than one and in the salt systems extraction efficiency was obtained up to 98% and in the case of polymer systems was obtained up to 8% at different tie-lines and it was found that the hydrophobicity of partitioned drugs is responsible for this phenomenon.

Milk-Derived Extracellular Vesicles: A Novel Perspective on Comparative Therapeutics and Targeted Nanocarrier Application

Milk-derived extracellular vesicles (mEVs) are emerging as promising therapeutic candidates due to their unique properties and versatile functions. These vesicles play a crucial role in immunomodulation by influencing macrophage differentiation and cytokine production, potentially aiding in the treatment of conditions such as bone loss, fibrosis, and cancer. mEVs also have the capacity to modulate gut microbiota composition, which may alleviate the symptoms of inflammatory bowel diseases and promote intestinal barrier integrity. Their potential as drug delivery vehicles is significant, enhancing the stability, solubility, and bioavailability of anticancer agents while supporting wound healing and reducing inflammation. Additionally, bovine mEVs exhibit anti-aging properties and protect skin cells from UV damage. As vaccine platforms, mEVs offer advantages including biocompatibility, antigen protection, and the ability to elicit robust immune responses through targeted delivery to specific immune cells. Despite these promising applications, challenges persist, including their complex roles in cancer, effective antigen loading, regulatory hurdles, and the need for standardized production methods. Achieving high targeting specificity and understanding the long-term effects of mEV-based therapies are essential for clinical translation. Ongoing research aims to optimize mEV production methods, enhance targeting capabilities, and conduct rigorous preclinical and clinical studies. By addressing these challenges, mEVs hold the potential to revolutionize vaccine development and targeted drug delivery, ultimately improving therapeutic outcomes across various medical fields.

Aqueous two-phase systems - versatile and advanced (bio)process engineering tools

Aqueous two-phase systems (ATPS), also known as Aqueous Biphasic Systems (ABS), have been extensively studied as platforms for the separation and purification of biomolecules and other valuable compounds. These liquid-liquid extraction (LLE) systems have been a tool for biotechnology since its origin (Albertsson, 1950's), recently expanding to exciting fields such as health, biomedicine and material sciences. Due to their biocompatibility, amenability, flexibility, and versatility, ATPS have been applied across various research areas, addressing many challenges associated with conventional methodologies. In this feature article, we first discuss the fundamentals of ATPS and the molecular mechanisms that govern their formation and are crucial for their application. We then explore the most prominent and innovative applications of these systems in downstream processing. Additionally, we provide insights into the design of in situ upstream-downstream integrated platforms, and their use as pre-treatment and analytical tools. The latest advancements in ATPS applications within disruptive bioengineering and biotechnology fields are presented, along with their pioneering use in emerging scientific areas, such as the formation of all-aqueous (water-in-water) emulsions, microfluidic systems, and membrane-free batteries. Overall, this work underscores the transformative potential of ATPS in various branches of science, pinpointing directions for future research to fully explore and maximize ATPS capabilities, overcome existing hurdles, and drive innovation forward.

Exploring the potential of all-aqueous immiscible systems for preparing complex biomaterials and cellular constructs

All-aqueous immiscible systems derived from liquid-liquid phase separation of incompatible hydrophilic agents such as polymers and salts have found increasing interest in the biomedical and tissue engineering fields in the last few years. The unique characteristics of aqueous interfaces, namely their low interfacial tension and elevated permeability, as well as the non-toxic environment and high water content of the immiscible phases, confer to these systems optimal qualities for the development of biomaterials such as hydrogels and soft membranes, as well as for the preparation of in vitro tissues derived from cellular assembly. Here, we overview the main properties of these systems and present a critical review of recent strategies that have been used for the development of biomaterials with increased levels of complexity using all-aqueous immiscible phases and interfaces, and their potential as cell-confining environments for micropatterning approaches and the bioengineering of cell-rich structures. Importantly, due to the relatively recent emergence of these areas, several key design considerations are presented, in order to guide researchers in the field. Finally, the main present challenges, future directions, and adaptability to develop advanced materials with increased biomimicry and new potential applications are briefly evaluated.

Advancements in Aqueous Two-Phase Systems for Enzyme Extraction, Purification, and Biotransformation

In recent years, the increasing need for energy conservation and environmental protection has driven industries to explore more efficient and sustainable processes. Liquid-liquid extraction (LLE) is a common method used in various sectors for separating components of liquid mixtures. However, the traditional use of toxic solvents poses significant health and environmental risks, prompting the shift toward green solvents. This review deals with the principles, applications, and advantages of aqueous two-phase systems (ATPS) as an alternative to conventional LLE. ATPS, which typically utilize water and nontoxic components, offer significant benefits such as high purity and single-step biomolecule extraction. This paper explores the thermodynamic principles of ATPS, factors influencing enzyme partitioning, and recent advancements in the field. Specific emphasis is placed on the use of ATPS for enzyme extraction, showcasing its potential in improving yields and purity while minimizing environmental impact. The review also highlights the role of ionic liquids and deep eutectic solvents in enhancing the efficiency of ATPS, making them viable for industrial applications. The discussion extends to the challenges of integrating ATPS into biotransformation processes, including enzyme stability and process optimization. Through comprehensive analysis, this paper aims to provide insights into the future prospects of ATPS in sustainable industrial practices and biotechnological applications.

Recent advances in drug delivery applications of aqueous two-phase systems

Aqueous two-phase systems (ATPSs) are liquid-liquid equilibria between two aqueous phases that usually contain over 70% water content each, which results in a nontoxic organic solvent-free environment for biological compounds and biomolecules. ATPSs have attracted significant interest in applications for formulating carriers (microparticles, nanoparticles, hydrogels, and polymersomes) which can be prepared using the spontaneous phase separation of ATPSs as a driving force, and loaded with a wide range of bioactive materials, including small molecule drugs, proteins, and cells, for delivery applications. This review provides a detailed analysis of various ATPSs, including strategies employed for particle formation, polymerization of droplets in ATPSs, phase-guided block copolymer assemblies, and stimulus-responsive carriers. Processes for loading various bioactive payloads are discussed, and applications of these systems for drug delivery are summarized and discussed.

What Can Be Learned from the Partitioning Behavior of Proteins in Aqueous Two-Phase Systems?

This review covers the analytical applications of protein partitioning in aqueous two-phase systems (ATPSs). We review the advancements in the analytical application of protein partitioning in ATPSs that have been achieved over the last two decades. Multiple examples of different applications, such as the quality control of recombinant proteins, analysis of protein misfolding, characterization of structural changes as small as a single-point mutation, conformational changes upon binding of different ligands, detection of protein-protein interactions, and analysis of structurally different isoforms of a protein are presented. The new approach to discovering new drugs for a known target (e.g., a receptor) is described when one or more previous drugs are already available with well-characterized biological efficacy profiles.

Metal ions: the unfading stars of bone regeneration-from bone metabolism regulation to biomaterial applications

In recent years, bone regeneration has emerged as a remarkable field that offers promising guidance for treating bone-related diseases, such as bone defects, bone infections, and osteosarcoma. Among various bone regeneration approaches, the metal ion-based strategy has surfaced as a prospective candidate approach owing to the extensive regulatory role of metal ions in bone metabolism and the diversity of corresponding delivery strategies. Various metal ions can promote bone regeneration through three primary strategies: balancing the effects of osteoblasts and osteoclasts, regulating the immune microenvironment, and promoting bone angiogenesis. In the meantime, the complex molecular mechanisms behind these strategies are being consistently explored. Moreover, the accelerated development of biomaterials broadens the prospect of metal ions applied to bone regeneration. This review highlights the potential of metal ions for bone regeneration and their underlying mechanisms. We propose that future investigations focus on refining the clinical utilization of metal ions using both mechanistic inquiry and materials engineering to bolster the clinical effectiveness of metal ion-based approaches for bone regeneration.