Is there a cause-and-effect relationship between physicochemical properties and cell behavior of alginate-based hydrogel obtained after sterilization?

Synergistic Antibacterial Action of Norfloxacin-Encapsulated G4 Hydrogels: The Role of Boronic Acid and Cyclodextrin

In this present study, we developed and characterized a series of supramolecular G4 hydrogels by integrating β-cyclodextrin (β-CD) and boronic acid linkers into a supramolecular matrix to enhance antibacterial activity against Staphylococcus aureus (S. aureus). We systematically investigated how varying the number of free boronic acid moieties (ranging from two to six), along with guanosine and β-CD content, influences both the structural integrity and antimicrobial efficacy of these materials. Comprehensive characterization using FTIR, circular dichroism, X-ray diffraction, SEM, AFM, and rheological measurements confirmed successful synthesis and revealed that higher boronic acid content correlated with a stronger, more organized network. The most effective hydrogel displayed an inhibition zone of 25 mm in disk diffusion assays, and was further explored as a drug delivery platform, with the aim to exploit the capacity of the free β-CD cavity of the hydrogels to incorporate hydrophobic drugs. Norfloxacin (Nfx), a poorly water-soluble antibiotic, was successfully encapsulated within the hydrogel matrix through the inclusion of complex formation with β-CD, improving its solubility and enabling sustained, targeted release. The Nfx-loaded hydrogel expanded the inhibition zone to 49 mm and completely eradicated S. aureus cells within 24 h, outperforming both the unloaded hydrogel and free Nfx. These results highlight the synergistic effect of boronic acid moieties and controlled drug release, underlining the potential of these hydrogels as versatile platforms for localized antimicrobial therapy, such as in wound dressings or implant coatings. Nevertheless, further in vivo studies and long-term stability assessments are needed to fully establish clinical relevance, safety, and scalability before these systems can be translated into routine healthcare applications.

Pulsed electromagnetic field-assisted reduced graphene oxide composite 3D printed nerve scaffold promotes sciatic nerve regeneration in rats

Peripheral nerve injuries can lead to sensory or motor deficits that have a serious impact on a patient's mental health and quality of life. Nevertheless, it remains a major clinical challenge to develop functional nerve conduits as an alternative to autologous grafts. We applied reduced graphene oxide (rGO) as a bioactive conductive material to impart electrophysiological properties to a 3D printed scaffold and the application of a pulsed magnetic field to excite the formation of microcurrents and induce nerve regeneration.In vitrostudies showed that the nerve scaffold and the pulsed magnetic field made no effect on cell survival, increased S-100βprotein expression, enhanced cell adhesion, and increased the expression level of nerve regeneration-related mRNAs.In vivoexperiments suggested that the protocol was effective in promoting nerve regeneration, resulting in functional recovery of sciatic nerves in rats, when they were damaged close to that of the autologous nerve graft, and increased expression of S-100β, NF200, and GAP43. These results indicate that rGO composite nerve scaffolds combined with pulsed magnetic field stimulation have great potential for peripheral nerve rehabilitation.

Protective Effect of Alginate Microcapsules with Different Rheological Behavior on Lactiplantibacillus plantarum 299v

Alginate encapsulation is a well-known technique used to protect microorganisms from adverse conditions. However, it is also known that the viscosity of the alginate is dependent on its composition and degree of polymerization and that thermal treatments, such as pasteurization and sterilization, can affect the structure of the polymer and decrease its protection efficiency. The goal of this study was to evaluate the protective effect of encapsulation, using alginates of different viscosities treated at different temperatures, on Lactiplantibacillus plantarum 299v under in vitro gastrointestinal conditions and cold storage at 4 °C and -15 °C, respectively. Steady- and dynamic-shear rheological tests were used to characterize the polymers. Thermal treatments profoundly affected the rheological characteristics of alginates with high and low viscosity. However, the solutions and gels of the low-viscosity alginate were more affected at a temperature of 117 °C. The capsules elaborated with high-viscosity alginate solution and pasteurized at 63 °C for 30 min provided better protection to the cells of L. plantarum 299v under simulated gastrointestinal and cold storage conditions.

A review of conventional and emerging technologies for hydrogels sterilization

Hydrogels are extensively used in the biomedical field, as drug delivery systems, wound dressings, contact lenses or as scaffolds for tissue engineering. Due to their polymeric nature and the presence of high amounts of water in their structure, hydrogels generally present high sensitivity to terminal sterilization. The establishment of an efficient sterilization protocol that does not compromise the functional properties of the hydrogels is one of the challenges faced by researchers when developing a hydrogel for a specific application. Yet, until very recently this aspect was largely ignored in the literature. The present paper reviews the state of literature concerning hydrogels sterilization, compiling the main findings. Conventional terminal sterilization methods (heat sterilization, radiation sterilization, and gas sterilization) as well as emerging sterilization techniques (ozone, supercritical carbon dioxide) are covered. Considerations about aseptic processing are also included. Additionally, and as a framework, hydrogels' polymeric materials, types of networks, and main biomedical applications are summarily described.

Structured Data Storage for Data-Driven Process Optimisation in Bioprinting

Bioprinting is a method to fabricate 3D models that mimic tissue. Future fields of application might be in pharmaceutical or medical context. As the number of applicants might vary between only one patient to manufacturing tissue for high-throughput drug screening, designing a process will necessitate a high degree of flexibility, robustness, as well as comprehensive monitoring. To enable quality by design process optimisation for future application, establishing systematic data storage routines suitable for automated analytical tools is highly desirable as a first step. This manuscript introduces a workflow for process design, documentation within an electronic lab notebook and monitoring to supervise the product quality over time or at different locations. Lab notes, analytical data and corresponding metadata are stored in a systematic hierarchy within the research data infrastructure Kadi4Mat, which allows for continuous, flexible data structuring and access management. To support the experimental and analytical workflow, additional features were implemented to enhance and build upon the functionality provided by Kadi4Mat, including browser-based file previews and a Python tool for the combined filtering and extraction of data. The structured research data management with Kadi4Mat enables retrospective data grouping and usage by process analytical technology tools connecting individual analysis software to machine-readable data exchange formats.

Viscoelastic parameters of invasive breast cancer in correlation with porous structure and elemental analysis data

BACKGROUND AND OBJECTIVE

Invasive ductal carcinoma (IDC) is the most common and aggressive type of breast cancer. As many clinical diagnoses are concerned with the tumor behavior at the compression, the IDC characterization using a compression test is performed in the present study. In the field of tissue characterization, most of the previous studies have focused on healthy and cancerous breast tissues at the cellular level; however, characterization of cancerous tissue at the tissue level has been under-represented, which is the target of the present study.

METHODS

Throughout this article, 18 IDC samples are tested using a ramp-relaxation test. The strain rate in the ramp phase is similar for all samples, whereas the strain level is set at 2,4 and 6%. The experimental stress-time data is interpolated by a viscoelastic model. Two relaxation times, as well as the instantaneous and long-term shear moduli, are calculated for each specimen.

RESULTS

The results show that the long-term and instantaneous shear moduli vary in the range of 0.31-17.03 kPa and 6.03-55.13 kPa, respectively. Our assessment of the viscoelastic parameters is accompanied by observing structural images of the IDCs and inspecting their elemental composition. It is concluded that IDCs with lower Magnesium to Calcium ratio (Mg:Ca) have smaller shear modulus and longer relaxation time, with a p-value of 0.001 and 0.01 for the correlation between Mg:Ca and long-term shear modulus, and Mg:Ca and early relaxation time.

CONCLUSIONS

Our identification of the IDC viscoelastic parameters can contribute to the IDC inspection at the tissue level. The results also provide useful information for modeling of breast cancer.

Low-energy electron beam sterilization of solid alginate and chitosan, and their polyelectrolyte complexes

Polysaccharidic scaffolds hold great hope in regenerative medicine, however their sterilization still remains challenging since conventional methods are deleterious. Recently, electron beams (EB) have raised interest as emerging sterilization techniques. In this context, the aim of this work was to study the impact of EB irradiations on polysaccharidic macroporous scaffolds. The effects of continuous and pulsed low energy EB were examined on polysaccharidic or on polyelectrolyte complexes (PEC) scaffolds by SEC-MALLS, FTIR and EPR. Then the scaffolds' physicochemical properties: swelling, architecture and compressive modulus were investigated. Finally, sterility and in vitro biocompatibility of irradiated scaffolds were evaluated to validate the effectiveness of our approach. Continuous beam irradiations appear less deleterious on alginate and chitosan chains, but the use of a pulsed beam limits the time of irradiation and better preserve the architecture of PEC scaffolds. This work paves the way for low energy EB tailor-made sterilization of sensitive porous scaffolds.

Multifaceted Optimization of MSC-Based Formulation upon Sodium Iodoacetate-Induced Osteoarthritis Models by Combining Advantageous HA/PG Hydrogel and Fluorescent Tracer

Owing to the boundedness of conventional remedies upon articular cartilage for self-rehabilitation and the incrementally senior citizens, the incidence of osteoarthritis (OA) is increasing worldwide. Empirical studies have revealed the advantageous and promising potentials of mesenchymal stem/stromal cells (MSCs) on the refractory OA, whereas the deficiency of systematic and detailed exploration of MSC-based therapy largely hampers the large-scale applications in regenerative medicine. Herein, we initially utilized the monosodium iodoacetate- (MIA-) induced OA rabbit models and investigated the therapeutic effect of human umbilical cord-derived UC-MSCs at serial dose gradients with the splendid hyaluronic acid and/or propylene glycol hydrogels (HA, HA/PG), respectively. Afterwards, we turned to a dual-luciferase reporter tracing system and evaluated the spatiotemporal distribution and metabolokinetics of bifluorescence expressing UC-MSCs (BF-MSCs) in OA rats. Of the aforementioned trials, we verified that the combination of HA/PG and middle-dose MSCs ( $0.5\times {10}^7$ cells/ml) eventually manifested the optimal efficacy on OA rabbits. Furthermore, with the aid of the bioluminescence imaging (BLI) technology for dynamic in vitro and in vivo tracking, we intuitively delineated the spatiotemporal distribution and therapeutic process of BF-MSCs in OA rats, which substantially confirmed the reinforcement of HA/PG on BF-MSCs for OA treatment. Collectively, our data conformably demonstrated that the middle dose of UC-MSCs combined with HA/PG hydrogel was sufficient for optimal MSC-based formulation for blocking OA progression and promoting cartilage repair, which supplied overwhelming new references and enlightened MSC-based therapeutic strategies for cartilage defects.

Effects of Autoclaving, EtOH, and UV Sterilization on the Chemical, Mechanical, Printability, and Biocompatibility Characteristics of Alginate

Sterilization is a necessary step during the processing of biomaterials, but it can affect the materials' functional characteristics. This study characterizes the effects of three commonly used sterilization processes-autoclaving (heat-based), ethanol (EtOH; chemical-based), and ultraviolet (UV; radiation-based)-on the chemical, mechanical, printability, and biocompatibility properties of alginate, a widely used biopolymer for drug delivery, tissue engineering, and other biomedical applications. Sterility assessment tests showed that autoclaving was effective against Gram-positive and Gram-negative bacteria at loads up to 10⁸ CFU/mL, while EtOH was the least effective. Nuclear magnetic-resonance spectroscopy showed that the sterilization processes did not affect the monomeric content in the alginate solutions. The differences in compressive stiffness of the three sterilized hydrogels were also not significant. However, autoclaving significantly reduced the molecular weight and polydispersity index, as determined via gel permeation chromatography, as well as the dynamic viscosity of alginate. Printability analyses showed that the sterilization process as well as the extrusion pressure and speed affected the number of discontinuities and spreading ratio in printed and cross-linked strands. Finally, human adipose-derived stem cells demonstrated over 90% viability in all sterilized hydrogels over 7 days, but the differences in cellular metabolic activity in the three groups were significant. Taken together, the autoclaving process, while demonstrating broad spectrum sterility effectiveness, also resulted in most notable changes in alginate's key properties. In addition to the specific results with the three sterilization processes and alginate, this study serves as a roadmap to characterize the interrelationships between sterilization processes, fundamental chemical properties, and resulting functional characteristics and processability of hydrogels.

Sterilization of hydrogels for biomedical applications: A review

Despite the beneficial properties and outstanding potential of hydrogels for biomedical applications, several unmet challenges must be overcome, especially regarding to their known sensitivity to conventional sterilization methods. It is crucial for any biomaterial to withstand an efficient sterilization to obtain approval from regulatory organizations and to safely proceed to clinical trials. Sterility assurance minimizes the incidence of medical device-related infections, which still constitute a major concern in health care. In this review, we provide a detailed and comprehensive description of the published work from the past decade regarding the effects of sterilization on different types of hydrogels for biomedical applications. Advances in hydrogel production methods with simultaneous sterilization are also reported. Terminal sterilization methods can induce negative or positive effects on several material properties (e.g., aspect, size, color, chemical structure, mechanical integrity, and biocompatibility). Due to the complexity of factors involved (e.g., material properties, drug stability, sterilization conditions, and parameters), it is important to note the virtual impossibility of predicting the outcome of sterilization methods to determine a set of universal rules. Each system requires case-by-case testing to select the most suitable, effective method that allows for the main properties to remain unaltered. The impact of sterilization methods on the intrinsic properties of these systems is understudied, and further research is needed. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2472-2492, 2018.