The review assesses two broad engineering approaches: exogenous conditioning and endogenous engineering. It also examines priming strategies, genetic modification and scalable culture systems, with particular attention to their potential benefits, limitations and clinical relevance. Programmable cargo loading is identified as a route toward more targeted therapeutic applications. However, improving the functional performance of MSC-EVs has not produced equivalent advances in product consistency or clinical manufacturability, leaving the development of standardized and scalable production processes unresolved.

Manufacturing controls discussed in the review include bioreactor and formulation strategies intended to enable larger-scale production of MSC-EVs. The analysis also identifies inconsistent isolation and quantification methods as important barriers. Standardized potency assays and clearly defined critical quality attributes are likewise needed to support reproducible assessment and manufacturing. The review does not report a new experiment or clinical result; instead, it evaluates how engineering strategies and bioprocess controls could be integrated to improve both therapeutic activity and translational feasibility.

Rather than treating efficacy and manufacturing as separate goals, the review proposes an integrated development framework. In this approach, vesicle engineering is linked with controllable risk, traceable quality and affordable cost, while quality control is incorporated into MSC-EV production workflows. The central conclusion is that the field’s progress will depend not simply on producing more functionally active vesicles, but on establishing manufacturing systems that can support consistent, reproducible and scalable therapeutics. The supplied evidence identifies these as development requirements rather than demonstrated clinical outcomes.

Subject of Research: Engineering and manufacturing control of mesenchymal stromal cell-derived extracellular vesicles

Article Title: Mesenchymal stromal cell-derived extracellular vesicles: engineering strategies and bioprocess controls for scalable and reproducible therapeutics

Article References: Wen, R., & Tang, B. (2026). Mesenchymal stromal cell-derived extracellular vesicles: engineering strategies and bioprocess controls for scalable and reproducible therapeutics. BioMedical Engineering OnLine. https://doi.org/10.1186/s12938-026-01628-0

Image Credits: AI Generated

DOI: 10.1186/s12938-026-01628-0

Keywords: MSC-derived extracellular vesicles, extracellular vesicle engineering, bioprocess control, scalable manufacturing, cargo loading, bioreactors, potency assays, critical quality attributes, reproducibility, cell-free therapeutics, Mesenchymal, stromal

Nanocrystal technology is one of the few bioavailability-enhancing strategies that has already been clinically validated and commercialized. The concept is straightforward: reduce the active pharmaceutical ingredient to particles in the nanometer range and stabilize their enormous surface energy with small amounts of polymers or surfactants. Because the drug itself is the carrier, nanocrystals achieve exceptionally high drug loading and can be adapted to many routes of administration, from oral tablets to injectable suspensions. According to the Noyes–Whitney relationship, dissolution rate increases as surface area grows, so nanosizing dramatically accelerates how quickly drug particles dissolve in the gastrointestinal tract. Beyond faster dissolution, nanocrystals also raise the apparent saturation solubility, since the increased surface free energy of very small particles creates a higher concentration gradient driving absorption, ultimately improving bioavailability for the poorly water-soluble compounds that dominate modern drug pipelines.

The review organizes the manufacturing landscape into three families of approaches. Top-down methods, such as wet media milling and high-pressure homogenization, break coarse crystals apart using mechanical forces. Wet media milling, in which drug suspensions are agitated with small grinding beads, is the workhorse of the industry because it is scalable, applies to nearly insoluble compounds and avoids organic solvents. Bottom-up methods, by contrast, build nanoparticles from dissolved molecules, most commonly through antisolvent precipitation, in which a drug solution is mixed with a poor solvent to trigger rapid nucleation. These approaches offer fine control over particle size but are sensitive to mixing dynamics and solvent removal challenges. Hybrid methods combine both principles—for example, precipitating a drug and then milling the resulting suspension—to exploit the strengths of each. The authors emphasize that each technique carries process-specific parameters that directly shape the critical quality attributes of the final product, from particle size distribution to dissolution behavior.

That sensitivity to process conditions is precisely why the review champions quality by design, or QbD, the regulatory philosophy codified in International Council for Harmonisation guidelines Q8, Q9 and Q12. Rather than testing quality into a finished product, QbD builds it in from the start. The workflow begins by defining a quality target product profile—the intended clinical performance of the medicine—and translating it into critical quality attributes such as particle size, zeta potential, crystallinity and dissolution rate. Risk assessment tools then identify which formulation variables, called critical material attributes, and which process parameters most strongly influence those attributes. Design of experiments is used to map the response surface, establish a design space within which quality is assured, and define control strategies that keep the process in its proven acceptable range throughout the product lifecycle.

Applied to wet media milling, the review’s flagship example, this framework becomes strikingly concrete. The quality target product profile dictates the critical quality attributes; milling parameters such as bead size, bead loading, milling speed, milling time, drug concentration and temperature are screened as critical process parameters. Stabilizer selection is treated with equal rigor: the type, concentration and physicochemical properties of polymers and surfactants are considered potential critical material attributes. Cellulosic polymers, poloxamers, polysorbates and even natural stabilizers such as tea saponins and proteins have all been explored, each interacting differently with the newly created crystal surfaces. The right stabilizer must wet the particles, adsorb rapidly onto fresh surfaces created during fracture, and provide either electrostatic or steric repulsion strong enough to prevent the particles from re-aggregating the moment milling stops.

Stabilization is not merely a matter of keeping particles apart; it is a battle against thermodynamics. The review details the principal physical instabilities that threaten nanosuspensions, including Ostwald ripening, in which small particles dissolve and redeposit onto larger ones because solubility increases with curvature, a phenomenon described classically by the Lifshitz–Slyozov–Wagner theory. Aggregation and sedimentation follow if the stabilizing layer is too weak, while uncontrolled crystallization can convert an amorphous surface layer back to a stable, slowly dissolving form. Because these instabilities accelerate with polydispersity and temperature, the choice of stabilizer concentration becomes a genuine design decision rather than a trial-and-error guess. QbD turns this chemistry into a controllable variable: by linking stabilizer attributes to measured quality outcomes through designed experiments, formulators can predict how a formulation will behave before it ever reaches the milling vessel.

Nanocrystal suspensions, however, are rarely the final dosage form. The review extends the QbD framework to solidification and scale-up, two stages where many promising formulations fail. Liquid nanosuspensions are physically fragile, so they are commonly converted into dry powders by spray drying, freeze-drying or fluidized bed coating onto carrier particles. Each drying method introduces its own risks: freeze-drying can cause particles to fuse during ice sublimation unless cryoprotectants are added, while spray drying exposes particles to heat and rapid evaporation that can induce aggregation or polymorphic changes. Scale-up compounds the difficulty, because milling efficiency depends on energy density and flow patterns that do not translate linearly from laboratory bead mills to production equipment. Mechanistic process modeling, the authors note, has been used to establish design spaces and control strategies for milled suspensions, offering a route to transfer a validated process across scales without re-deriving it from scratch.

The industrial credentials of the technology are substantial. Nanocrystal-based products have reached the market across multiple therapeutic areas and administration routes, including long-acting injectable suspensions for psychiatric and oncology indications, oral formulations and dermal applications. Recent research continues to expand the frontier: nanocrystals embedded in hydrogels for intratympanic delivery of dexamethasone to treat hearing loss, transdermal systems for rotigotine and meloxicam, ophthalmic suspensions, pulmonary formulations of budesonide, and even veterinary and agricultural uses such as herbicide nanosuspensions that suppress Ostwald ripening in the field. In oncology, sterile nanosuspensions of mebendazole and other agents are being explored for brain tumor therapy, while QbD-optimized nanocrystals of sotorasib, a KRAS inhibitor, demonstrate how modern targeted cancer drugs with extreme insolubility can be rescued by nanosizing combined with biosurfactant stabilization.

The review’s expert opinion distills a decade of accumulated evidence into a single message: nanocrystal development should be viewed as an integrated process in which particle properties, stabilization mechanisms, preparation methods, solidification and scale-up are closely interconnected. Treating these elements in isolation, the authors argue, is what historically made nanocrystal formulation slow and unpredictable. QbD supplies the connective tissue—a systematic understanding of how formulation variables and process parameters jointly determine quality attributes, enabling predictive development rather than iterative guesswork. As regulatory agencies worldwide continue to encourage lifecycle management and continuous improvement under ICH Q12, the authors conclude that QbD-based predictive development and quality control strategies will improve developmental efficiency and, crucially, accelerate the industrial and clinical translation of nanocrystal medicines, turning one of pharmaceutical science’s most versatile tools into a reliably engineered platform for the next generation of poorly soluble drugs.

Subject of Research: Application of quality by design principles to drug nanocrystal formulation, stabilization, manufacturing and industrial translation

Article Title: Application of quality by design in drug nanocrystal development: principles, stabilization, manufacturing strategies, and industrial applications

Article References: Jeong, J.-S., Ha, E.-S., Kim, J.-S., Yoon, N.-Y., Jung, H.-W., Kim, M.-G., Nam, J., Shin, E., Park, H., & Kim, M.-S. (2026). Application of quality by design in drug nanocrystal development: principles, stabilization, manufacturing strategies, and industrial applications. Journal of Pharmaceutical Investigation. https://doi.org/10.1007/s40005-026-00834-1

Image Credits: AI Generated

DOI: 10.1007/s40005-026-00834-1

Keywords: drug nanocrystals, quality by design, poorly water-soluble drugs, wet media milling, stabilizers, critical quality attributes, Ostwald ripening, bioavailability enhancement, spray drying, freeze-drying, pharmaceutical manufacturing, nanosuspensions

The research, led by Alessandra Colombini and Laura de Girolamo of the Orthopaedic Biotechnology Lab at IRCCS Galeazzi-Sant’Ambrogio Hospital in Milan, together with colleagues in Bari, Palermo, Turin, and Switzerland, set out to build a manufacturing framework that satisfies Good Manufacturing Practice, or GMP, the regulatory standard required for any cell therapy destined for patients. The team focused on chondrocytes, the specialized cells that produce and maintain cartilage matrix, and on a supplement called human platelet lysate, or hPL. Platelet lysate is produced from donated blood platelets that are ruptured to release their cargo of growth factors, and it has emerged as a leading candidate to replace fetal bovine serum, the traditional but problematic culture supplement that carries risks of immune reactions and pathogen transmission.

What distinguishes the new work is its insistence on treating cell expansion not as a laboratory art but as a controlled industrial process with defined critical quality attributes, abbreviated CQAs. In the language of pharmaceutical manufacturing, CQAs are the measurable properties a final product must possess to be safe and effective. For a chondrocyte therapy, those properties include the ability to proliferate robustly, a low immunogenic profile, retention of progenitor-associated surface markers, and, crucially, the capacity to deposit a proper cartilage-like extracellular matrix once the cells are returned to a three-dimensional environment. The Milan-led team designed their entire expansion protocol around preserving these attributes rather than simply maximizing cell numbers.

The experimental core of the study involved expanding human chondrocytes under low-density culture conditions in media supplemented with two different hPL formulations. Low-density seeding is a deliberate strategic choice. When cartilage cells are grown too densely, they tend to lose their specialized character and drift toward a fibroblast-like state, a phenomenon known as dedifferentiation that has plagued autologous chondrocyte implantation for decades. By keeping cells sparse, the researchers encouraged them to retain progenitor-like features. Their flow cytometry and marker analyses showed that the expanded populations expressed CD146 and CD166, surface molecules associated with chondrocyte progenitor cells, particularly under the low-density regime, while maintaining a low immunogenic profile that bodes well for autologous and potentially allogeneic applications.

To understand what the two platelet lysate formulations were actually delivering to the cells, the team turned to high-resolution mass spectrometry, profiling the protein composition of individual hPL batches and then applying bioinformatic analyses to identify differentially abundant proteins and enriched biological pathways. The results were striking: the two formulations differed significantly in their protein makeup, even though both supported efficient cell expansion. This finding carries an important manufacturing lesson. Two batches of hPL that perform similarly in a proliferation assay may nonetheless be biologically distinct, and a GMP-compliant process cannot afford to leave that variability uncharacterized. Proteomic batch characterization, the study suggests, belongs among the quality controls of any clinical-grade cell expansion protocol that relies on platelet lysate.

The decisive test of any expanded chondrocyte population is whether it can still make cartilage. The researchers addressed this by transferring the expanded cells into three-dimensional spheroid cultures, a format that mimics the condensed cell masses of early cartilage development. Histological and immunohistochemical analyses of the resulting spheroids revealed preserved chondrogenic capacity, with optimal extracellular matrix deposition observed at a seeding density of 200,000 cells per well. Both hPL conditions supported the production of type II collagen, the hallmark structural protein of hyaline cartilage, which is the tissue clinicians most want to regenerate. However, the two formulations produced measurable differences in glycosaminoglycan content, the charged sugar molecules that give cartilage its compressive resilience, and in type I collagen, a fibrous protein whose abundance can signal a shift toward less desirable, scar-like repair tissue.

On top of the biological optimization, the team implemented a formal risk-based manufacturing strategy using Failure Modes and Effects Analysis, or FMEA, a structured methodology borrowed from engineering and aerospace in which every step of a process is systematically scored for what could go wrong, how likely it is, and how severe the consequences would be. Applied to chondrocyte expansion, the FMEA identified the critical process parameters, or CPPs, that most strongly influence product quality, along with the associated risks at each stage. The analysis then pointed to targeted mitigation strategies, allowing the researchers to link each critical quality attribute to the process parameters that control it. This traceability, from risk to parameter to quality attribute, is precisely the architecture regulators expect when evaluating an advanced therapy medicinal product, or ATMP, for clinical trials.

The significance of the framework extends beyond cartilage. ATMPs, which include cell and gene therapies, are among the most heavily scrutinized products in medicine, and many promising candidates have stalled not because they failed in patients but because their manufacturing could not be made reproducible, scalable, and compliant. By demonstrating that biologically optimized culture conditions can be integrated with a structured risk assessment into a single GMP-compatible workflow, the Italian and Swiss consortium has provided a template that other cell therapy developers can adapt. The work was supported by the Italian Ministry of Health through its Ricerca Corrente funding program, and the study received ethics approval from the San Raffaele Hospital Ethics Committee, with written informed consent collected from all participants.

The authors are careful about where their findings sit on the translational timeline. The framework, they conclude, supports further preclinical validation and contributes to the development of scalable, clinically applicable therapies for cartilage repair, with a particular eye toward patients with early osteoarthritis, a population in which cell-based intervention has the best chance of altering disease course before joint damage becomes irreversible. Preclinical validation will need to confirm that the expanded, progenitor-enriched cells perform reliably in appropriate models, and eventual clinical studies will test whether the carefully preserved chondrogenic phenotype translates into durable cartilage repair in the joint. Still, the study resolves one of the field’s most persistent bottlenecks: it shows that human platelet lysate can support clinically compliant chondrocyte expansion without sacrificing the biological qualities that make the therapy worth manufacturing in the first place.

For the millions of people whose knees and other joints are slowly eroded by osteoarthritis, the study is a reminder that regenerative medicine advances as much through unglamorous process engineering as through biological discovery. The growth factors flooding a culture dish, the density at which cells are seeded, the batch-to-batch protein signature of a blood-derived supplement, and the failure modes of every handling step together determine whether a cartilage cell therapy reaches the operating room or dies in development. By mapping that entire landscape with proteomics, spheroid assays, and formal risk analysis, the researchers have turned a fragile laboratory procedure into something resembling a manufacturable medicine, and in doing so they have moved cartilage repair a tangible step closer to routine clinical practice.

Subject of Research: GMP-compliant expansion of human chondrocytes supplemented with human platelet lysate for cartilage repair

Article Title: Risk-based framework for GMP-compatible low-density platelet lysate-supplemented expansion of human cartilage cells for tissue repair

Article References: Colombini, A., Lopa, S., Raffo, V., Lo Pinto, M., Scilabra, S. D., Ferrero, I., Castiglia, S., Mareschi, K., Mangiavini, L., Moretti, M., & de Girolamo, L. (2026). Risk-based framework for GMP-compatible low-density platelet lysate-supplemented expansion of human cartilage cells for tissue repair. Journal of Translational Medicine. https://doi.org/10.1186/s12967-026-08827-2

Image Credits: AI Generated

DOI: 10.1186/s12967-026-08827-2

Keywords: chondrocytes, cartilage repair, human platelet lysate, GMP manufacturing, advanced therapy medicinal products, risk-based framework, FMEA, critical quality attributes, osteoarthritis, regenerative medicine, proteomics, cell therapy