Bio-friendly encapsulation of superoxide dismutase into vaterite CaCO3 crystals. Enzyme activity, release mechanism, and perspectives for ophthalmology

Influence of natural polysaccharides on the morphology and properties of hybrid vaterite microcrystals

Co-precipitation of biopolymers into calcium carbonate crystals changes their physicochemical and biological properties. This work studies hybrid microcrystals of vaterite obtained in the presence of natural polysaccharides, as carriers for the delivery of proteins and enzymes. Hybrid microcrystals with dextran sulfate, chondroitin sulfate, heparin, fucoidan, and pectin were obtained and compared. The impact of polysaccharides on the morphology (particle diameter, surface area, nanocrystallite and pore size), polysaccharide content and surface charge of hybrid microcrystals was studied. Only microcrystals with fucoidan and heparin exhibited antioxidant activity against •ОН radical. The surface charge and pore size of the hybrid microcrystals affected the sorption of albumin, catalase, chymotrypsin, mucin. A decrease in the catalytic constant and Michaelis constant was observed for catalase sorbed on the hybrid crystals. The biocompatibility of microcrystals depended on the nature of the included polysaccharide: crystals with sulfated polysaccharides increased blood plasma coagulation but not platelet aggregation, and crystals with dextran sulfate had the greatest cytotoxicity against HT-29 cells but not erythrocytes. Hybrid microcrystals with all polysaccharides except chondroitin sulfate reduced erythrocyte lysis in vitro compared with vaterite crystals. The obtained results enable to create novel carriers based on hybrid vaterite crystals with polysaccharides, beneficial for the delivery of protein drugs.

Functionalized Calcium Carbonate-Based Microparticles as a Versatile Tool for Targeted Drug Delivery and Cancer Treatment

Nano- and microparticles are increasingly widely used in biomedical research and applications, particularly as specific labels and targeted delivery vehicles. Silica has long been considered the best material for such vehicles, but it has some disadvantages limiting its potential, such as the proneness of silica-based carriers to spontaneous drug release. Calcium carbonate (CaCO3) is an emerging alternative, being an easily available, cost-effective, and biocompatible material with high porosity and surface reactivity, which makes it an attractive choice for targeted drug delivery. CaCO3 particles are used in this field in the form of either bare CaCO3 microbeads or core/shell microparticles representing polymer-coated CaCO3 cores. In addition, they serve as removable templates for obtaining hollow polymer microcapsules. Each of these types of particles has its specific advantages in terms of biomedical applications. CaCO3 microbeads are primarily used due to their capacity for carrying pharmaceutics, whereas core/shell systems ensure better protection of the drug-loaded core from the environment. Hollow polymer capsules are particularly attractive because they can encapsulate large amounts of pharmaceutical agents and can be so designed as to release their contents in the target site in response to specific stimuli. This review focuses first on the chemistry of the CaCO3 cores, core/shell microbeads, and polymer microcapsules. Then, systems using these structures for the delivery of therapeutic agents, including drugs, proteins, and DNA, are outlined. The results of the systematic analysis of available data are presented. They show that the encapsulation of various therapeutic agents in CaCO3-based microbeads or polymer microcapsules is a promising technique of drug delivery, especially in cancer therapy, enhancing drug bioavailability and specific targeting of cancer cells while reducing side effects. To date, research in CaCO3-based microparticles and polymer microcapsules assembled on CaCO3 templates has mainly dealt with their properties in vitro, whereas their in vivo behavior still remains poorly studied. However, the enormous potential of these highly biocompatible carriers for in vivo applications is undoubted. This last issue is addressed in depth in the Conclusions and Outlook sections of the review.

Hybrid protein microspheres and their responsive release behaviors and inhibitory effects on melanin synthesis

In this study, the formation of protein microspheres through lysosomal enzyme-assisted biomineralized crystallization was demonstrated. Spherical micro-sized hybrid CaCO3 constructs were synthesized and characterized using field-emission scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and particle size analysis. Additionally, parameters such as the Brunauer-Emmett-Teller surface area and single-point total pore volume, and adsorption/desorption analysis were used to investigate the mesoporous properties, which are advantageous for lysosomal enzyme (LE) loading. A LE can be used as an organic template, not only as a morphological controller but also for entrapping LE during the crystallization pathway. The hybrid protein microspheres accommodated 2.3 mg of LE with a 57% encapsulation efficiency and 5.1 wt% loading. The peroxidase activity of the microspheres was calculated and found to be approximately 0.0238 mM-1 min-1. pH-responsive release of the LE from CaCO3 was observed, suggesting potential biomedical and cosmetic applications in acidic environments. The hybrid LE microsphere treatment significantly alleviated melanin production in a dose-dependent manner and further downregulated the mRNA expression of MITF, tyrosinase, TYRP-1, and TYRP-2. These results indicate skin-whitening effects by inhibiting melanin without inducing cytotoxicity. The data provide the first evidence of the potential use of a LE for obtaining hybrid minerals and the effectiveness of biomineralization-based sustainable delivery of enzyme-based vehicles based on organelle-extract-assisted biomineralization.

Green and effective remediation of heavy metals contaminated water using CaCO3 vaterite synthesized through biomineralization

Heavy metal pollution has attracted significant attention due to its persistent presence in aquatic environments. A novel vaterite-based calcium carbonate adsorbent, named biogenic CaCO3, was synthesized utilizing a microbially induced carbonate precipitation (MICP) method to remediate heavy metal-contaminated water. The maximum Cd2+ removal capacity of biogenic CaCO3 was 1074.04 mg Cd2+/g CaCO3 with a high Cd2+ removal efficiency greater than 90% (initial Cd2+ concentration 400 mg/L). Furthermore, the biogenic CaCO₃ vaterite, induced by microbial-induced calcium carbonate precipitation (MICP) process, demonstrated a prolonged phase transformation to calcite and enhanced stability. This resulted in a sustained high effectiveness (greater than 96%) following six consecutive recycling tests. Additionally, X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses revealed that the semi-stable vaterite type of biogenic CaCO3 spontaneously underwent dissolution and recrystallization to form thermodynamic stable calcite in aquatic environments. However, the presence of Cd2+ leads to the transformation of vaterite into CdCO3 rather than undergoing direct converting to calcite. This transformation is attributed to the relatively low solubility of CdCO3 compared to calcite. Meanwhile, the biogenic CaCO3 proved to be an efficient and viable method for the removal of Pb2+, Cu2+, Zn2+, Co2+, Ni2+ and Mn2+ from water samples, surpassing the performance of previously reported adsorbents. Overall, the efficient and promising adsorbent demonstrates potential for practical in situ remediation of heavy metals-contaminated water.

Polyethylenimine-CO2 adduct templated CaCO3 nanoparticles as anticancer drug carrier

Background

Due to their porous structure and capability to degrade under acidic conditions, CaCO3 nanoparticles in vaterite form can be used as carriers to effectively deliver drugs to low-pH sites such as tumors. The usually used intravenous administration requires long-term vaterite phase and colloidal stability for storage and blood circulation. While passive accumulation in tumors can be achieved via the enhanced permeation and retention effect, active accumulation requires reactive groups on vaterite nanoparticles to conjugate targeting molecules. Both requirements are hard to achieve in one simple and economical vaterite formulation. Herein, we used polyethylenimine (PEI)-based CO2 adduct as both a CO2 source and a template for vaterite mineralization to generate PEI-CO2@CaCO3 colloidal particles, with reactive amino groups from the PEI template.

Results

The obtained nanoparticles with a hydrodynamic diameter of 200–300 nm have a vaterite phase and colloidal stability in an aqueous solution for over 8 months. These nanoparticles could effectively load anticancer drug doxorubicin via coprecipitation and be surface-modified with polyethylene glycol (PEG) and folic acid for long-term blood circulation and tumor targeting purposes, respectively. After being endocytosed, the PEI-CO2 adduct accelerates the dissolution of drug-loaded nanoparticles to generate CO2 bubbles to break the lysosomes, leading to rapid doxorubicin delivery inside tumor cells. The degradation of PEI-CO2 in the CaCO3 nanoparticles could also release PEI and CO2 and may contribute to the disruption of normal cellular functions. As a result, the drug-loaded PEI-CO2@CaCO3 nanoparticles strongly suppressed tumor growth in mice with HeLa tumor xenografts.

Conclusions

A new and effective vaterite drug carrier for anticancer therapy has been developed using PEI-CO2 adduct as both a CO2 source and vaterite template for CaCO3 mineralization. This delivery system illustrates an application of CO2 generation materials in drug delivery and has the potential for further development.

Incorporation of Pectin into Vaterite Microparticles Prevented Effects of Adsorbed Mucin on Neutrophil Activation

The application of vaterite microparticles for mucosal delivery depends on their interaction with mucin and immune cells. As we have shown previously, the binding of mucin onto particles enhances the generation of reactive oxygen species by neutrophils. The attenuation of the pro-oxidant effect of the bound mucin through the modification of vaterite could improve its biocompatibility. Hybrid microparticles composed of vaterite and pectin (CCP) were prepared using co-precipitation. In comparison with vaterite (CC), they had a smaller diameter and pores, a greater surface area, and a negative zeta-potential. We aimed to study the cytotoxicity and mucin-dependent neutrophil-activating effect of CCP microparticles. The incorporated pectin did not influence the neutrophil damage according to a lactate dehydrogenase test. The difference in the CC- and CCP-elicited luminol or lucigenin chemiluminescence of neutrophils was insignificant, with no direct pro- or antioxidant effects from the incorporated pectin. Unlike soluble pectin, the CCP particles were ineffective at scavenging radicals in an ABAP-luminol test. The fluorescence of SYTOX Green demonstrated a CCP-stimulated formation of neutrophil extracellular traps (NETs). The pre-treatment of CC and CCP with mucin resulted in a 2.5-times-higher CL response of neutrophils to the CC-mucin than to the CCP-mucin. Thus, the incorporation of pectin into vaterite microspheres enabled an antioxidant effect to be reached when the neutrophils were activated by mucin-treated microparticles, presumably via exposed ligands.

Exploiting Benefits of Vaterite Metastability to Design Degradable Systems for Biomedical Applications

The widespread application of calcium carbonate is determined by its high availability in nature and simplicity of synthesis in laboratory conditions. Moreover, calcium carbonate possesses highly attractive physicochemical properties that make it suitable for a wide range of biomedical applications. This review provides a conclusive analysis of the results on using the tunable vaterite metastability in the development of biodegradable drug delivery systems and therapeutic vehicles with a controlled and sustained release of the incorporated cargo. This manuscript highlights the nuances of vaterite recrystallization to non-porous calcite, dissolution at acidic pH, biodegradation at in vivo conditions and control over these processes. This review outlines the main benefits of vaterite instability for the controlled liberation of the encapsulated molecules for the development of biodegradable natural and synthetic polymeric materials for biomedical purposes.

Oral delivery of a highly stable superoxide dismutase as a skin aging inhibitor

As an effective antioxidant enzyme, superoxide dismutase (SOD) has been widely used as a food supplement, cosmetic additive, and therapeutic agent. However, oral delivery of SOD is challenging due to its relative instability, limited bioavailability, and low absorption efficiency in the gastrointestinal (GI) tract. We addressed these issues using a highly stable superoxide dismutase (hsSOD) generated from a hot spring microbial sample. This SOD exhibited a specific activity of 5000 IU/mg while retaining its enzymatic activity under low pH environments of an artificial GI system and in the presence of surfactants and various proteolytic enzymes. The inhibitory effects of hsSOD against skin-aging was evaluated under both in vitro and in vivo experiments using fibroblast cell and D-galactose induced aging-mouse models, respectively. Effective oral delivery of hsSOD promises wide applicability in pharmaceutical and food industries.

Spontaneous shrinkage drives macromolecule encapsulation into layer-by-layer assembled biopolymer microgels

HYPOTHESIS

Recently, the anomalous shrinkage of surface-supported hyaluronate/poly-l-lysine (HA/PLL) microgels (µ-gels), which exceeds that reported for any other multilayer-based systems, has been reported [1]. The current study investigates the capability of these unique µ-gels for the encapsulation and retention of macromolecules, and proposes the shrinkage-driven assembly of biopolymer-based µ-gels as a novel tool for one-step surface biofunctionalization.

EXPERIMENTS

A set of dextrans (DEX) and their charged derivatives - carboxymethyl (CM)-DEX and diethylaminoethyl (DEAE)-DEX - has been utilized to evaluate the effects of macromolecular mass and net charge on µ-gel shrinkage and macromolecule entrapment. µ-gels formation on the surface of silicone catheters exemplifies their potential to tailor biointerfaces.

FINDINGS

Shrinkage-driven µ-gel formation strongly depends on the net charge and mass content of encapsulated macromolecules. Inclusion of neutral DEX decreases the degree of shrinkage several times, whilst charged DEXs adopt to the backbone of oppositely charged polyelectrolytes, resulting in shrinkage comparable to that of non-loaded µ-gels. Retention of CM-DEX in µ-gels is significantly higher compared to DEAE-DEX. These insights into the mechanisms of macromolecular entrapment into biopolymer-based µ-gels promotes fundamental understanding of molecular dynamics within the multilayer assemblies. Organization of biodegradable µ-gels at biomaterial surfaces opens avenues for their further exploitation in a diverse array of bioapplications.

Nano-Microemulsions of CaCO3-Encapsulated Curcumin Ester Derivatives With High Antioxidant and Antimicrobial Activities and pH Sensitivity

In this study, we synthesized nano-microemulsions of calcium carbonate (CaCO3)-encapsulated curcumin (Cur)-Ferulic acid (FA) ester derivatives of diverse mass ratios by using the solution casting approach. The structures, antioxidant and antimicrobial activities, physical properties, and potential of hydrogen (pH) sensitivity of these products were examined. Compared with microparticles of CaCO3, those of CaCO3@Cur-FA exhibited excellent antimicrobial and antioxidant properties. Response to pH was indicated through the release of Cur-FA from CaCO3@Cur-FA in solutions having different pH values. The results demonstrated that Cur-FA was released more quickly from CaCO3@Cur-FA at pH 5.5 than at pH 7.4. CaCO3@Cur-FA demonstrated good antioxidant capacities through its ability to scavenge 2,2′-amino-di(2-ethyl-benzothiazoline sulphonic acid-6)ammonium salt (ABTS+) and 1,1-diphenyl-2-picrylhydrazyl (DPPH). These activities were three-fold more than those observed in CaCO3 microparticle control groups; additionally, the antimicrobial activity against Aspergillus niger and Escherichia coli increased by 40.5 and 54.6%, respectively. Overall, the microparticles of CaCO3@Cur-FA outperformed Cur-FA in terms of antimicrobial properties by inhibiting the growth of certain zoonotic pathogens.

Calcium carbonate vaterite particles for drug delivery: Advances and challenges

The recent successful application of lipid-based nanoparticles as delivery vehicles in COVID-19 vaccines demonstrated the superior potential of nanoparticle-based technology for targeted drug delivery in biomedicine. Among novel, rapidly advancing delivery platforms, the inorganic nano/microparticles gradually reach new heights and attract well-deserved attention among scientists and clinicians. Calcium carbonate in its vaterite form is used as a biocompatible carrier for a progressively increasing number of biomedical applications. Its growing popularity is conferred by beneficial porosity of particles, high mechanical stability, biodegradability under certain physiological conditions, ability to provide a continuous steady release of bioactives, preferential safety profile, and low cost, which make calcium carbonate a suitable entity of highly efficacious formulations for controlled drug delivery and release. The focal point of the current review is the success of the recent vaterite applications in the delivery of various diagnostics and therapeutic drugs. The manuscript highlights the nuances of drug loading in vaterite particles, connecting it with particle morphology, size, and charge of the loaded molecules, payload concentration, mono- or multiple drug loading. The manuscript also depicts recent successful methods of increasing the loading capacity developed for vaterite carriers. In addition, the review describes the various administration routes for vaterite particles with bioactive payloads, which were reported in recent years. Special attention is given to the multi-drug-loaded vaterite particles ("molecular cocktails") and reports on their successful delivery in vitro and in vivo.

Hybrid Mucin-Vaterite Microspheres for Delivery of Proteolytic Enzyme Chymotrypsin

While the enteral delivery of proteolytic enzymes is widely established for combating many diseases as an alternative to antibiotic treatment, their local delivery only emerges as administration route enabling sustained release in a controlled manner on site. The latest requires the development of drug delivery systems suitable for encapsulation and preservation of enzymatic proteolytic activity. This study proposes hybrid microspheres made of mucin and biodegradable porous crystals of calcium carbonate (CC) as the carriers for chymotrypsin (CTR) delivery. CTR was impregnated into CC and hybrid CC/mucin (CCM) microspheres by means of sorption without any chemical modification. The loading of the CC with mucin enhances CTR retention on hybrid microspheres (adsorption capacity of ca 8.7 versus 4.7 mg/g), recharging crystal surface due to the presence of mucin and diminishing the average pore diameter of the crystals from 25 to 8 nm. Mucin also retards recrystallization of vaterite into non-porous calcite improving stability of CCM microspheres upon storage. Proteolytic activity of CTR is preserved in both CC and CCM microspheres, being pH dependent. Temperature-induced inactivation of CTR significantly diminishes by CTR encapsulation into CC and CCM microspheres. Altogether, these findings indicate promises of hybrid mucin-vaterite microspheres for mucosal application of proteases. This article is protected by copyright. All rights reserved.

Hard, Soft, and Hard-and-Soft Drug Delivery Carriers Based on CaCO3 and Alginate Biomaterials: Synthesis, Properties, Pharmaceutical Applications

Because free therapeutic drug molecules often have adverse effects on normal tissues, deliver scanty drug concentrations and exhibit a potentially low efficacy at pathological sites, various drug carriers have been developed for preclinical and clinical trials. Their physicochemical and toxicological properties are the subject of extensive research. Inorganic calcium carbonate particles are promising candidates as drug delivery carriers owning to their hardness, porous internal structure, high surface area, distinctive pH-sensitivity, low degradability, etc, while soft organic alginate hydrogels are also widely used because of their special advantages such as a high hydration, bio-adhesiveness, and non-antigenicity. Here, we review these two distinct substances as well as hybrid structures encompassing both types of carriers. Methods of their synthesis, fundamental properties and mechanisms of formation, and their respective applications are described. Furthermore, we summarize and compare similarities versus differences taking into account unique advantages and disadvantages of these drug delivery carriers. Moreover, rational combination of both carrier types due to their performance complementarity (yin-&yang properties: in general, yin is referred to for definiteness as hard, and yang is broadly taken as soft) is proposed to be used in the so-called hybrid carriers endowing them with even more advanced properties envisioned to be attractive for designing new drug delivery systems.

Recent Strategies for the Immobilization of Therapeutic Enzymes

Therapeutic enzymes play important roles in modern medicine due to their high affinity and specificity. However, it is very expensive to use them in clinical medicine because of their low stability and bioavailability. To improve the stability and effectiveness of therapeutic enzymes, immobilization techniques have been employed to enhance the applications of therapeutic enzymes in the past few years. Reported immobilization techniques include entrapment, adsorption, and covalent attachment. In addition, protein engineering is often used to improve enzyme properties; however, all methods present certain advantages and limitations. For carrier-bound immobilization, the delivery and release of the immobilized enzyme depend on the properties of the carrier and enzyme. In this review, we summarize the advantages and challenges of the current strategies developed to deliver therapeutic enzymes and provide a future perspective on the immobilization technologies used for therapeutic enzyme delivery.

Modification of Surfaces with Vaterite CaCO3 Particles

Former studies have demonstrated a strong interest toward the crystallization of CaCO₃ polymorphs in solution. Nowadays, CaCO₃ crystallization on solid surfaces is extensively being studied using biomolecules as substrates for the control of the growth aiming at various applications of CaCO₃. Calcium carbonate exists in an amorphous state, as three anhydrous polymorphs (aragonite, calcite and vaterite), and as two hydrated polymorphs (monohydrocalcite and ikaite). The vaterite polymorph is considered as one of the most attractive forms due to its large surface area, biocompatibility, mesoporous nature, and other features. Based on physical or chemical immobilization approaches, vaterite can be grown directly on solid surfaces using various (bio)molecules, including synthetic polymers, biomacromolecules such as proteins and peptides, carbohydrates, fibers, extracellular matrix components, and even biological cells such as bacteria. Herein, the progress on the modification of solid surfaces by vaterite CaCO₃ crystals is reviewed, focusing on main findings and the mechanism of vaterite growth initiated by various substances mentioned above, as well as the discussion of the applications of such modified surfaces.

CaCO3-based carriers with prolonged release property for antifungal drug delivery to hair follicles

Superficial fungal infections are of serious concern worldwide due to their morbidity and increasing distribution across the globe in this era of growing antimicrobial resistance. Delivery of antifungals to target...

Nanotechnology for Topical Drug Delivery to the Anterior Segment of the Eye

Topical drug delivery is one of the most challenging aspects of eye therapy. Eye drops are the most prevalent drug form, especially for widely distributed anterior segment eye diseases (cataracts, glaucoma, dry eye syndrome, inflammatory diseases, etc.), because they are convenient and easy to apply by patients. However, conventional drug formulations are usually characterized by short retention time in the tear film, insufficient contact with epithelium, fast elimination, and difficulties in overcoming ocular tissue barriers. Not more than 5% of the total drug dose administered in eye drops reaches the interior ocular tissues. To overcome the ocular drug delivery barriers and improve drug bioavailability, various conventional and novel drug delivery systems have been developed. Among these, nanosize carriers are the most attractive. The review is focused on the different drug carriers, such as synthetic and natural polymers, as well as inorganic carriers, with special attention to nanoparticles and nanomicelles. Studies in vitro and in vivo have demonstrated that new formulations could help to improve the bioavailability of the drugs, provide sustained drug release, enhance and prolong their therapeutic action. Promising results were obtained with drug-loaded nanoparticles included in in situ gel.

Barnase encapsulation into submicron porous CaCO3 particles: studies of loading and enzyme activity

The present study focuses on the immobilization of the bacterial ribonuclease barnase (Bn) into submicron porous calcium carbonate (CaCO₃) particles. For encapsulation, we apply adsorption, freezing-induced loading and co-precipitation methods and study the effects of adsorption time, enzyme concentration and anionic polyelectrolytes on the encapsulation efficiency of Bn. We show that the use of negatively charged dextran sulfate (DS) and ribonucleic acid from yeast (RNA) increases the loading capacity (LC) of the enzyme on CaCO₃ particles by about 3-fold as compared to the particles with Bn itself. The ribonuclease (RNase) activity of encapsulated enzyme depends on the LC of the particles and transformation of metastable vaterite to stable calcite, as studied by the assessment of enzyme activities in particles.

Biopolymer-Based Multilayer Capsules and Beads Made via Templating: Advantages, Hurdles and Perspectives

One of the undeniable trends in modern bioengineering and nanotechnology is the use of various biomolecules, primarily of a polymeric nature, for the design and formulation of novel functional materials for controlled and targeted drug delivery, bioimaging and theranostics, tissue engineering, and other bioapplications. Biocompatibility, biodegradability, the possibility of replicating natural cellular microenvironments, and the minimal toxicity typical of biogenic polymers are features that have secured a growing interest in them as the building blocks for biomaterials of the fourth generation. Many recent studies showed the promise of the hard-templating approach for the fabrication of nano- and microparticles utilizing biopolymers. This review covers these studies, bringing together up-to-date knowledge on biopolymer-based multilayer capsules and beads, critically assessing the progress made in this field of research, and outlining the current challenges and perspectives of these architectures. According to the classification of the templates, the review sequentially considers biopolymer structures templated on non-porous particles, porous particles, and crystal drugs. Opportunities for the functionalization of biopolymer-based capsules to tailor them toward specific bioapplications is highlighted in a separate section.

Doxorubicin delivery systems based on doped CaCO3 cores and polyanion drug conjugates

In order to prolong the release and reduce the toxicity of anticancer drug - doxorubicin (DOX), delivery systems (DS) using different polyanions have been developed. Structural (size, morphological stability) and functional (encapsulation efficiency, DOX release) characteristics of three types of DS are compared: CaCO₃ porous vaterites doped with polyanions by co-precipitation and coating techniques, and DOX-polyanion conjugates. Using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), it was shown that the doping enhances the morphological stability of CaCO₃-based DS during the DOC loading. Doping of CaCO₃ cores by co-precipitation reduces its sizes (up to 1 µm) and DOX encapsulation efficiency. Polyanion-coated CaCO₃ cores and polyanion drug conjugates show about 98 w/w% DOX encapsulation. For the first time, it was shown that the release of DOX from developed DS into human blood plasma is more intense (from 1.3 to 3.0 times for different DS) than into model tumour environment.

Evaluating enzyme stabilizations in calcium carbonate: Comparing in situ and crosslinking mediated immobilization

Enzyme immobilization using inorganic materials has been shown to preserve enzyme activity improving and improve their practical applications in biocatalytic process designs. Proper immobilization methods have been used to obtain high recycling and storage stability. In this study, we compared the activity and stability of in situ or crosslink-immobilized enzymes in a CaCO₃ biomineral carrier. More than 30% of the initial enzyme activity was preserved for both the systems after 180 days upon 15 activity measurements at room temperature, confirming the improved stability of these enzyme systems (100 mM phosphate buffer, pH 8.0); however, differences in enzyme loading, activity, and characteristics were observed for each of these methods. Each system exhibited efficacy of 80% and 20%, respectively. Based on the same amount of immobilized enzyme (0.2 mg), the specific activities of hydrolysis of p-nitrophenyl butyrate substrate at room temperature of in situ immobilized carboxyl esterase (CE) and crosslinked CE were 11.37 and 7.63 mM min^-1 mg^-1, respectively (100 mM phosphate buffer, pH 8.0). Moreover, based on the kinetic behavior, in situ immobilized CE exhibited improved catalytic efficiency (Vmax Km^-1) of the enzyme, exhibiting 4-fold higher activity and efficiency values than those of the CE immobilized in CaCO₃. This is the first study to describe the stabilization of enzymes in CaCO₃ and compare the enzyme kinetics and efficiencies between in situ immobilization and crosslinking in CaCO₃ carriers.

Which Biopolymers Are Better for the Fabrication of Multilayer Capsules? A Comparative Study Using Vaterite CaCO3 as Templates

The polymer layer-by-layer assembly is accounted among the most attractive approaches for the design of advanced drug delivery platforms and biomimetic materials in 2D and 3D. The multilayer capsules can be made of synthetic or biologically relevant (e.g., natural) polymers. The biopolymers are advantageous for bioapplications; however, the design of such "biocapsules" is more challengeable due to intrinsic complexity and lability of biopolymers. Until now, there are no systematic studies that report the formation mechanism for multilayer biocapsules templated upon CaCO₃ crystals. This work evaluates the structure-property relationship for 16 types of capsules made of different biopolymers and proposes the capsule formation mechanism. The capsules have been fabricated upon mesoporous cores of vaterite CaCO₃, which served as a sacrificial template. Stable capsules of polycations poly-l-lysine or protamine and four different polyanions were successfully formed. However, capsules made using the polycation collagen and dextran amine underwent dissolution. Formation of the capsules has been correlated with the stability of the respective polyelectrolyte complexes at increased ionic strength. All formed capsules shrink upon core dissolution and the degree of shrinkage increased in the series of polyanions: heparin sulfate < dextran sulfate < chondroitin sulfate < hyaluronic acid. The same trend is observed for capsule adhesiveness to the glass surface, which correlates with the decrease in polymer charge density. The biopolymer length and charge density govern the capsule stability and internal structure; all formed biocapsules are of a matrix-type, other words are microgels. These findings can be translated to other biopolymers to predict biocapsule properties.

Cooling-Triggered Release from Mesoporous Poly(N-isopropylacrylamide) Microgels at Physiological Conditions

Poly(N-isopropylacrylamide) (pNIPAM) hydrogels have broad potential applications as drug delivery vehicles because of their thermoresponsive behavior. pNIPAM loading/release performances are directly affected by the gel network structure. Therefore, there is a need with the approaches for accurate design of 3D pNIPAM assemblies with the structure ordered at the nanoscale. This study demonstrates size-selective spontaneous loading of macromolecules (dextrans 10-500 kDa) into pNIPAM microgels by microgel heating from 22 to 35 °C (microgels collapse and trap dextrans) followed by the dextran release upon further cooling down to 22 °C (microgels swell back) . This temperature-mediated behavior is fully reversible. The structure of pNIPAM microgels was tailored via hard templating and cross-linking of the hydrogel using sacrificial mesoporous cores of vaterite CaCO3 microcrystals. In addition, the fabrication of hollow thermoresponsive pNIPAM microshells has been demonstrated, utilizing vaterite microcrystals that had narrower pores. The proposed approach for heating-triggered encapsulation and cooling-triggered release into/from pNIPAM microgels may pave the ways for applications of pNIPAM hydrogels for skin and transdermal cooling-responsive drug delivery in the future.

Transdermal platform for the delivery of the antifungal drug naftifine hydrochloride based on porous vaterite particles

Development of a skin-targeted particulate delivery system providing an extended or sustained release of the payload and a localized therapeutic effect is one of the main challenges in the treatment of fungal skin infections. In the topical administration of antifungals, the drug should penetrate into the stratum corneum and lower layers of the skin in effective concentrations. Here, we introduce biodegradable calcium carbonate carriers containing 4.9% (w/w) of naftifine hydrochloride antimycotic allowing the efficient accumulation into the skin appendages. The proposed particulate formulation ensures the enhancement of the local drug concentration, prolongation of the payload release, and control over its rate. Furthermore, it provides a highly efficient cellular uptake and excellent bioavailability in vitro and enables a deep penetration during transfollicular delivery in vivo. The enhanced fungi growth inhibition efficiency of naftifine-loaded calcium carbonate carriers compared to naftifine solution makes them a promising alternative to creams and gels currently existing on the market.

Improvement in the Pharmacological Profile of Copper Biological Active Complexes by Their Incorporation into Organic or Inorganic Matrix

Every year, more Cu(II) complexes are proven to be biologically active species, but very few are developed as drugs or entered in clinical trials. This is due to their poor water solubility and lipophilicity, low stability as well as in vivo inactivation. The possibility to improve their pharmacological and/or oral administration profile by incorporation into inorganic or organic matrix was studied. Most of them are either physically encapsulated or conjugated to the matrix via a moiety able to coordinate Cu(II). As a result, a large variety of species were developed as delivery carriers. The organic carriers include liposomes, synthetic or natural polymers or dendrimers, while the inorganic ones are based on carbon nanotubes, hydrotalcite and silica. Some hybrid organic-inorganic materials based on alginate-carbonate, gold-PEG and magnetic mesoporous silica-Schiff base were also developed for this purpose.

Immobilization and Stabilization of Enzyme in Biomineralized Calcium Carbonate Microspheres

Biomineralized uniform and well-organized calcium carbonate microspheres were synthesized for enzyme immobilization, and the immobilized enzyme was successfully stabilized. The physicochemical parameters of calcium carbonate were studied using scanning electron microscopy with energy-dispersive X-ray spectroscopy, particle size analysis, X-ray diffraction analysis, Fourier-transform infrared spectroscopy, and surface area measurement. Additionally, Barrett-Joyner-Halenda adsorption/desorption analysis showed that the calcium carbonate microspheres provided efficient mesopore space for enzyme loading. As a model enzyme, carboxyl esterase (CE) was entrapped and then cross-linked to form an enzyme structure. In this aggregate, the cross-linked enzymes cannot leach out from mesopores, resulting in enzyme stability. The hydrolytic activities of the free and cross-linked enzymes were analyzed over broad temperature and pH ranges. The cross-linked enzyme displayed better activity than the free enzyme. Furthermore, the immobilized CE was found to be stable for more than 30 days, preserving 60% of its initial activity even after being reused more than 10 times. This report is expected to be the first demonstration of a stabilized cross-linked enzyme system in calcium carbonate microspheres, which can be applied in enzyme catalyzed reactions involved in bioprocessing, bioremediation, and bioconversion.

CaCO3 crystals as versatile carriers for controlled delivery of antimicrobials

CaCO₃ crystals have been known for a long time as naturally derived and simply fabricated nano(micro)-sized materials able to effectively host and release various molecules. This review summarises the use of CaCO₃ crystals as versatile carriers to host, protect and release antimicrobials, offering a strong tool to tackle antimicrobial resistance, a serious global health problem. The main methods for the synthesis of CaCO₃ crystals with different properties, as well as the approaches for the loading and release of antimicrobials are presented. Finally, prospects to utilize the crystals in order to improve the therapeutic outcome and combat antimicrobial resistance are highlighted. Ultimately, this review intends to provide an in-depth overview of the application of CaCO₃ crystals for the smart and controlled delivery of antimicrobial agents and aims at identifying the advantages and drawbacks as well as guiding future works, research directions and industrial applications.

Polyelectrolyte Multilayer Capsule (PEMC)-Based Scaffolds for Tissue Engineering

Tissue engineering (TE) is a highly multidisciplinary field that focuses on novel regenerative treatments and seeks to tackle problems relating to tissue growth both in vitro and in vivo. These issues currently involve the replacement and regeneration of defective tissues, as well as drug testing and other related bioapplications. The key approach in TE is to employ artificial structures (scaffolds) to support tissue development; these constructs should be capable of hosting, protecting and releasing bioactives that guide cellular behaviour. A straightforward approach to integrating bioactives into the scaffolds is discussed utilising polyelectrolyte multilayer capsules (PEMCs). Herein, this review illustrates the recent progress in the use of CaCO3 vaterite-templated PEMCs for the fabrication of functional scaffolds for TE applications, including bone TE as one of the main targets of PEMCs. Approaches for PEMC integration into scaffolds is addressed, taking into account the formulation, advantages, and disadvantages of such PEMCs, together with future perspectives of such architectures.

Encapsulation of Low-Molecular-Weight Drugs into Polymer Multilayer Capsules Templated on Vaterite CaCO3 Crystals

Polyelectrolyte multilayer capsules (PEMCs) templated onto biocompatible and easily degradable vaterite CaCO₃ crystals via the layer-by-layer (LbL) polymer deposition process have served as multifunctional and tailor-made vehicles for advanced drug delivery. Since the last two decades, the PEMCs were utilized for effective encapsulation and controlled release of bioactive macromolecules (proteins, nucleic acids, etc.). However, their capacity to host low-molecular-weight (LMW) drugs (<1–2 kDa) has been demonstrated rather recently due to a limited retention ability of multilayers to small molecules. The safe and controlled delivery of LMW drugs plays a vital role for the treatment of cancers and other diseases, and, due to their tunable and inherent properties, PEMCs have shown to be good candidates for smart drug delivery. Herein, we summarize recent progress on the encapsulation of LMW drugs into PEMCs templated onto vaterite CaCO₃ crystals. The drug loading and release mechanisms, advantages and limitations of the PEMCs as LMW drug carriers, as well as bio-applications of drug-laden capsules are discussed based upon the recent literature findings.

Inter-protein interactions govern protein loading into porous vaterite CaCO3 crystals

Loading of therapeutic proteins into mesoporous vaterite crystals is driven by inter-protein interactions in bulk solution and inside the crystals.

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.