Advanced Nanomaterials-Assisted Cell Cryopreservation: A Mini Review

Engineering Magnetic Nanoclusters for Highly Efficient Heating in Radio-Frequency Nanowarming

Effective thawing of cryopreserved samples requires rapid and uniform heating. This is achievable through nanowarming, an approach that heats magnetic nanoparticles by using alternating magnetic fields. Here we demonstrate the synthesis and surface modification of magnetic nanoclusters for efficient nanowarming. Magnetite (Fe3O4) nanoclusters with an optimal diameter of 58 nm exhibit a high specific absorption rate of 1499 W/g Fe under an alternating magnetic field at 43 kA/m and 413 kHz, more than twice that of commercial iron oxide cores used in prior nanowarming studies. Surface modification with a permeable resorcinol-formaldehyde resin (RFR) polymer layer significantly enhances their colloidal stability in complex cryoprotective solutions, while maintaining their excellent heating capacity. The Fe3O4@RFR nanoparticles achieved a high average heating rate of 175 °C/min in cryopreserved samples at a concentration of 10 mg Fe/mL and were successfully applied in nanowarming porcine iliac arteries, highlighting their potential for enhancing the efficacy of cryopreservation.

Environmental behaviors and toxic mechanisms of engineered nanomaterials in soil

Engineered nanomaterials (ENMs) are inevitably released into the environment with the exponential application of nanotechnology. Parts of ENMs eventually accumulate in the soil environment leading to potential adverse effects on soil ecology, crop production, and human health. Therefore, the safety application of ENMs on soil has been widely discussed in recent years. More detailed safety information and potential soil environmental risks are urgently needed. However, most of the studies on the environmental effects of metal-based ENMs have been limited to single-species experiments, ecosystem processes, or abiotic processes. The present review formulated the source and the behaviors of the ENMs in soil, and the potential effects of single and co-exposure ENMs on soil microorganisms, soil fauna, and plants were introduced. The toxicity mechanism of ENMs to soil organisms was also reviewed including oxidative stress, the release of toxic metal ions, and physical contact. Soil properties affect the transport, transformation, and toxicity of ENMs. Toxic mechanisms of ENMs include oxidative stress, ion release, and physical contact. Joint toxic effects occur through adsorption, photodegradation, and loading. Besides, future research should focus on the toxic effects of ENMs at the food chain levels, the effects of ENMs on plant whole-lifecycle, and the co-exposure and long-term toxicity effects. A fast and accurate toxicity evaluation system and model method are urgently needed to solve the current difficulties. It is of great significance for the sustainable development of ENMs to provide the theoretical basis for the ecological risk assessment and environmental management of ENMs.

Freezing and thawing of cells on a microfluidic device: a simple and time-saving experimental procedure

Developing cell cryopreservation methods on chips is not only crucial for biomedical science but also represents an innovative approach for preserving traditional cell samples. This study presents a simple method for direct cell freezing and thawing on chip, allowing for long-term storage of cells. During the freezing process, cells were injected into the microchannel along with a conventional cell cryopreservation solution, and the chip was packed using a self-sealing bag containing isopropyl alcohol and then stored in a -80°C refrigerator until needed. During the thawing process, microcolumn arrays with a spacing of 8 µm were strategically incorporated into the microfluidic chip design to effectively inhibit cells from the channel. The breast cancer cell lines MDA-MB-231 and B47D demonstrated successful thawing and growth after cryopreservation for 1 month to 1 year. These findings offer a direct cell freezing and thawing method on a microfluidic chip for subsequent experiments.

Control strategies of ice nucleation, growth, and recrystallization for cryopreservation

The cryopreservation of biomaterials is fundamental to modern biotechnology and biomedicine, but the biggest challenge is the formation of ice, resulting in fatal cryoinjury to biomaterials. To date, abundant ice control strategies have been utilized to inhibit ice formation and thus improve cryopreservation efficiency. This review focuses on the mechanisms of existing control strategies regulating ice formation and the corresponding applications to biomaterial cryopreservation, which are of guiding significance for the development of ice control strategies. Herein, basics related to biomaterial cryopreservation are introduced first. Then, the theoretical bases of ice nucleation, growth, and recrystallization are presented, from which the key factors affecting each process are analyzed, respectively. Ice nucleation is mainly affected by melting temperature, interfacial tension, shape factor, and kinetic prefactor, and ice growth is mainly affected by solution viscosity and cooling/warming rate, while ice recrystallization is inhibited by adsorption or diffusion mechanisms. Furthermore, the corresponding research methods and specific control strategies for each process are summarized. The review ends with an outlook of the current challenges and future perspectives in cryopreservation. STATEMENT OF SIGNIFICANCE: Ice formation is the major limitation of cryopreservation, which causes fatal cryoinjury to cryopreserved biomaterials. This review focuses on the three processes related to ice formation, called nucleation, growth, and recrystallization. The theoretical models, key influencing factors, research methods and corresponding ice control strategies of each process are summarized and discussed, respectively. The systematic introduction on mechanisms and control strategies of ice formation is instructive for the cryopreservation development.

Surface Engineering Promoted Insulin-Sensitizing Activities of Sub-Nanoscale Vanadate Clusters through Regulated Pharmacokinetics and Bioavailability

The therapeutic application of vanadium compounds is plagued by their poor bioavailability and potential adverse effects. Herein, 1 nm polyoxovanadate (POV) clusters are functionalized with alkyl chains of various lengths and studied for the effect of surface engineering on their preclinical pharmacokinetics and typical insulin-sensitizing activity. The concentrations of surface engineered POVs in plasma, urine, and feces are monitored after a single administration to rats. The POVs exhibit a two-compartment profile of in vivo kinetics, and the surface engineering effect plays an important role in renal clearance of the POVs comparable to small molecules. POVs functionalized with long alkyl chains show much shorter elimination half time t_1/2β and higher elimination fractions (50%) within 48 h than pristine POVs, suggesting favorable elimination kinetics to mitigate the possible side effects of vanadium. Meanwhile, long alkyl chain modification leads to a 76% increment of oral bioavailability in contrast to unmodified POVs. As suggested by glucose tolerance tests and sub-chronic toxicity tests, the above two factors contribute to the enhanced therapeutic efficacy of POVs while mitigating their adverse effects. The surface engineering protocol provides a feasible approach to the optimization of the bioavailability and pharmacokinetic properties of POVs for promoted insulin-sensitizing activities.

Engineering living cells with cucurbit[7]uril-based supramolecular polymer chemistry: from cell surface engineering to manipulation of subcellular organelles

Supramolecular polymer chemistry, which closely integrates noncovalent interactions with polymeric structures, is a promising toolbox for living cell engineering. Here, we report our recent progress in exploring the applications of cucurbit[7]uril (CB[7])-based supramolecular polymer chemistry for engineering living cells. First, a modular polymer-analogous approach was established to prepare multifunctional polymers that contain CB[7]-based supramolecular recognition motifs. The supramolecular polymeric systems were successfully applied to cell surface engineering and subcellular organelle manipulation. By anchoring polymers on the cell membranes, cell–cell interactions were established by CB[7]-based host–guest recognition, which further facilitated heterogeneous cell fusion. In addition to cell surface engineering, placing the multifunctional polymers on specific subcellular organelles, including the mitochondria and endoplasmic reticulum, has led to enhanced physical contact between subcellular organelles. It is highly anticipated that the CB[7]-based supramolecular polymer chemistry will provide a new strategy for living cell engineering to advance the development of cell-based therapeutic materials.

Cucurbit[7]uril-based supramolecular polymer chemistry, which closely integrates host–guest recognition with multifunctional polymeric structures, is a promising toolbox for living cell engineering.

Poly(l-Ala-co-l-Lys) Exhibits Excellent Ice Recrystallization Inhibition Activity

The control of ice recrystallization is very important in cryo-technological fields such as the food industry, biopharmaceuticals, and cell storage. Ice recrystallization inhibition (IRI) compounds are therefore designed to limit the growth of ice crystals, decrease the crystal size, and control the crystal shape. To improve the IRI activity of cryo-systems, various synthetic polymers such as biomimetic polypeptides from polar fish, facially amphiphilic polymers, polyampholytes, poly(vinyl alcohol) derivatives, and block copolymers with hydrophilic-hydrophobic balance have been developed. Except for graphene oxide, poly(vinyl alcohol) has thus far exhibited the best performance among these polymers. Herein, poly(l-alanine-co-l-lysine) (PAK) was shown to exhibit a similar IRI activity to that of poly(vinyl alcohol). Moreover, in contrast to the needle-shaped ice crystals generated by the aqueous PVA solution, the PAK solution was shown to generate cubic-to-spherical shaped ice crystals. Furthermore, neither poly(l-alanine-co-l-aspartic acid) (PAD) nor poly(ethylene glycol) (PEG) with a similar molecular weight provided any significant IRI activity. Examination by FTIR and circular dichroism spectroscopies indicated that the PAK forms α-helices, whereas the PAD forms random coils in water. Further, a dynamic ice shaping study suggested that PAK strongly interacts with ice crystals, whereas PAD and PEG only weakly interact. These results suggest that PAK is an important compound with superior IRI activity and that this activity is dependent upon the functional groups and secondary structure of the polypeptides.

Synthesis, self-aggregation and cryopreservation effects of perylene bisimide-glycopeptide conjugates

Three perylene bisimide-glycopeptide conjugates (PBI-AFF-Man, PBI-AFF-Glu and PBI-AFF-Gal) were synthesized, which showed moderate activity in the control of ice crystal growth. Furthermore, the cellular cryopreservation effects of PBI-AFF-Man, PBI-AFF-Glu and PBI-AFF-Gal showed enhancements in cell viabilities, especially for PBI-AFF-Glu with values of 22.77 ± 3.33% (HeLa cells), 19.43 ± 1.90% (A549 cells) and 16.63 ± 1.76% (GES-1 cells) at a dose of 1.0 mg mL^-1. This work will help guide the development of self-assembled cryoprotectants.