Testosterone replacement therapy (TRT) has evolved dramatically over the past decade. Once dominated by weekly intramuscular injections or messy gels, the field is now shaped by biotechnological innovations that deliver hormones more safely, consistently and conveniently. But where do these cutting‑edge therapies come from? This article takes you behind the scenes to explore how breakthrough TRT tools are designed and manufactured—from hormone‑filled microbeads produced with aqueous encapsulation to gene therapy vectors cultured in giant bioreactors and AI algorithms trained to personalize dosing. Understanding the science and craftsmanship behind these products helps patients make more informed decisions and appreciate the rigor that goes into modern hormone care.

Why New Delivery Technologies Are Needed

Standard TRT methods—such as long‑acting injections, transdermal gels and patches, and subcutaneous implants—restore testosterone levels but have significant drawbacks. Injections deliver a large dose every one to two weeks, causing peaks and troughs that lead to mood swings and inconsistent symptom control. Gels and patches risk skin irritation or transfer to partners. Pellets require minor surgery and can extrude or cause infections. Oral capsules historically suffered from poor bioavailability and potential liver toxicity. To overcome these limitations, researchers, engineers and pharmaceutical manufacturers are reinventing how hormones are produced and delivered.

Crafting Hormone‑Filled Microbeads With Core‑Shell Spherification

The problem with oil‑based microbeads

Microbeads—tiny spheres that encapsulate hormones and release them slowly—promise long‑acting effects without surgery. Earlier methods formed microbeads using oil emulsions or complex microfluidic devices. These techniques were not easily scalable and relied on non‑biocompatible oils that could irritate tissue and complicate manufacturing. As Lisa Stehno‑Bittel (Likarda) and Charles Virden (VitalTE) explained in a 2025 Drug Target Review article, oil emulsion techniques resulted in droplets with oil residues that are unsafe for injectable hormone products.

Core‑Shell Spherification: an aqueous alternative

Likarda addressed these challenges by developing Core‑Shell Spherification (CSS), a spray technology that uses a fully aqueous system to create hormone‑filled hydrogel microspheres. Here’s how this process works:

1. Preparing the hydrogel: A biocompatible polymer—often hyaluronic acid or alginate—is dissolved in water to form a viscous hydrogel solution. The hormone (e.g., testosterone) is suspended inside the solution, sometimes in the form of tiny liposomes or nanoparticles to protect it from immediate exposure.
   
2. Spray encapsulation: The hydrogel–hormone mixture is sprayed through a nozzle into a cross‑linking solution (often containing calcium ions). As droplets hit the solution, the calcium ions trigger ionic cross‑linking, forming a stable hydrogel shell around each droplet. Because the entire process occurs in water, there is no oil residue and the beads are fully biocompatible.
   
3. Controlled size and shape: By adjusting nozzle diameter, flow rate, and spray pressure, manufacturers control bead size from a few micrometres to several hundred micrometres. Uniform beads ensure consistent release rates and dosing.
   
4. Drying or storage: The beads may be dried for storage or kept in a buffer solution until use. Their water content allows them to be injected easily.
   

The result is an injectable hydrogel microbead that degrades slowly. Instead of exposing the hormone to tissue immediately, the hydrogel acts as a barrier. As it breaks down, the encapsulated testosterone diffuses steadily into the bloodstream. Pre‑clinical studies show this approach can extend a peptide’s half‑life from 12 hours to 10 days or more, depending on the hydrogel design. Essentially, microbeads behave like micropellets—providing extended release without surgery and with minimal irritation.

Manufacturing considerations

Producing microbeads at scale demands stringent quality control. The CSS process avoids oil and uses simple spray equipment, making it more scalable than microfluidics. Yet manufacturers must ensure consistent bead size, cross‑linking density and hormone loading. They do this by monitoring viscosity, spray pressure and cross‑linking bath composition. Batch testing confirms that beads release hormone at the intended rate and remain sterile.

3D‑Printed Microbeads: Drop‑on‑Demand Manufacturing

Another approach to microbead manufacture uses drop‑on‑demand 3D printing. Researchers at the University of Bern developed a method to print biodegradable microbeads containing liposomes for sustained drug release. Though their work targeted peritoneal diseases, the principles apply to hormone therapy. The process involves:

1. Formulating a printable ink: The team mixed alginate hydrogel with liposomes encapsulating a drug. They optimized the ink’s viscosity and viscoelastic properties to ensure it could be extruded through a print nozzle. Viscosity values below 100 mPa·s were too fluid, causing droplets to merge; values above 250 mPa·s were too thick for extrusion. A viscosity window between roughly 100 mPa·s and 250 mPa·s produced spherical beads.
   
2. Drop‑on‑demand printing: Using an electromagnetically controlled printhead, they jetted micro‑ to nanolitre droplets into a cross‑linking bath. Adjusting nozzle diameter, pressure and actuation time allowed precise control over droplet size and shape. This “drop‑on‑demand” approach means droplets are generated only when needed, reducing waste.
   
3. Cross‑linking and stabilization: The printed droplets entered a calcium chloride bath, which cross‑linked the alginate to form stable beads. Liposomes remained trapped within the hydrogel because the gel’s mesh size (10–100 nm) is smaller than the liposome diameter. The researchers compared different lipids and found that soybean‑derived phosphatidylcholine (S80) offered high drug encapsulation efficiency (around 90 %) at certain lipid-to-drug ratios.
   
4. Characterization: After printing, beads were examined under light and scanning electron microscopes to ensure uniform size and shape. Rheological tests and design-of-experiment strategies helped optimize the ink formulation and printing parameters.
   

Although still experimental, drop‑on‑demand printing illustrates how microbead manufacturing can be precise and customizable. Such techniques could be adapted to produce microbeads containing testosterone or other hormones, enabling patient‑specific dosing and release profiles.

How Oral Testosterone Capsules Are Crafted

Traditional oral testosterone formulations were ineffective because the hormone degraded in the liver. Testosterone undecanoate (Kyzatrex) solves this problem by using a lipid‑based delivery system that is absorbed through the lymphatic system rather than the portal vein. While exact manufacturing details are proprietary, the basic steps include:

1. Selecting the active ingredient: Testosterone is esterified with undecanoic acid to form testosterone undecanoate. This ester increases lipophilicity, promoting lymphatic absorption.
   
2. Preparing a lipid matrix: A mixture of lipids (such as medium‑chain triglycerides) and surfactants forms the capsule’s self‑emulsifying system. When the capsule contacts stomach fluids, it forms a microemulsion that solubilizes the ester.
   
3. Filling and sealing softgels: The lipid–drug mixture is filled into soft gelatin capsules under nitrogen to prevent oxidation. Capsules are sealed and dried. The result is a softgel that dissolves in the gut, allowing the lipid droplets to pass into the lymphatic system and avoid first‑pass liver metabolism. This yields approximately 90 % bioavailability and maintains normal testosterone levels for most users.
   
4. Quality control: Manufacturers test each batch for uniformity, potency, and dissolution properties. They also assess stability and ensure no contamination.
   

This pharmaceutical engineering ensures that oral capsules deliver therapeutic levels without harming the liver—an advance only possible through careful formulation science.

Inside a Gene Therapy Factory: Manufacturing AAV Vectors

One of the most ambitious frontiers in testosterone restoration involves gene therapy. Researchers at Peking University used an adeno‑associated virus (AAV) vector—AAVDJ‑Lhcgr—to deliver a functional Lhcgr gene to Leydig cell precursors in mice, restoring testosterone production and fertility. Producing such gene therapy vectors requires complex biomanufacturing.

Production platforms for AAV vectors

A 2025 review article explains that most clinical‑grade AAVs are manufactured using one of three platforms:

• Viral infection–based mammalian platforms: Established cell lines (e.g., HEK293 or BHK) are co‑infected with two recombinant herpes simplex viruses. One carries the therapeutic gene flanked by AAV inverted terminal repeats (ITRs); the other carries the Rep and Cap genes needed for AAV assembly. While this method can achieve high yields (~10^11 vector genomes/mL), it is rarely used today because of safety concerns and complex virus handling.
  
• Stable producer cell lines: Here, the necessary AAV genes are integrated into the genome of mammalian cells. Only a wild‑type adenovirus is needed to provide helper functions; the rest of the production machinery is built into the cell. These lines scale well and require less plasmid DNA, but they still involve infectious viruses and need extensive cell line development.
  
• Transient transfection of HEK293 cells: Currently the most common method (used for ~69 % of clinical trials), this approach transfects HEK293 cells with three plasmids: one carrying the therapeutic gene flanked by ITRs, one encoding Rep and Cap, and one containing adenoviral helper genes. The plasmids form complexes with transfection reagents such as polyethyleneimine. This system is flexible because different genes and capsid serotypes can be swapped easily. However, it is sensitive to transfection conditions and requires large quantities of plasmid DNA.
  

An alternative baculovirus expression vector system (BEVS) uses recombinant baculoviruses to infect insect cells (Sf9). This system can achieve titers up to 10^12 vector genomes/mL and yields high ratios of full to empty capsids. BEVS is widely used because insect cells grow in suspension and require less expensive media. However, genetic instability of baculoviruses and differences in post‑translational modifications can affect vector properties.

Purification and quality control

After production, AAV particles must be separated from host cell proteins, DNA and empty capsids. Historically, ultracentrifugation with toxic density gradients was used. Newer methods employ affinity chromatography and ion‑exchange columns to purify vectors. Manufacturing facilities test the final product for potency (vector genome titer), purity (ratio of full to empty capsids), and safety (absence of helper viruses or contaminants). These processes must comply with Good Manufacturing Practice (GMP) regulations before the vector can enter clinical trials.

Behind Personalized Dosing Algorithms

Artificial intelligence has become a central component of modern TRT. Personalized dosing systems analyze a patient’s hormone levels, genetics, lifestyle factors and real‑time data from wearables to recommend optimized treatment schedules. Developing these algorithms involves several steps:

1. Data collection: Clinics collect large datasets from patients—blood test results, body mass index, age, activity levels, sleep quality and medication adherence. Some programs also incorporate genetic polymorphisms affecting hormone metabolism.
   
2. Model training: Machine learning engineers train algorithms on this data to predict how different doses affect serum testosterone, mood, energy and side effects. Techniques such as supervised learning and reinforcement learning help tailor algorithms to individual responses.
   
3. Integration with devices: Wearable sensors send continuous data on heart rate, sleep, stress and blood pressure to AI platforms. When combined with lab results, these inputs allow real‑time adjustment of dosing.
   
4. Human oversight and ethics: Clinicians supervise AI recommendations and ensure that dosing changes make clinical sense. Data privacy safeguards and bias mitigation strategies are critical to protect patient information.
   

AI‑driven personalization not only improves symptom control but also reduces trial‑and‑error, making TRT more efficient and patient‑centered.

Designing Microdosing Injection Devices

Microdosing delivers smaller amounts of testosterone more frequently, keeping serum levels steady. Modern devices simplify this process. Auto‑injectors use spring‑loaded or electronically driven mechanisms to deliver precise subcutaneous doses at the push of a button. Some incorporate digital displays or smartphone connectivity to remind patients of dosing schedules and record injection history. Though specific manufacturing details vary by brand, devices are assembled under sterile conditions and must meet strict quality standards for accuracy, reliability and bio‑compatibility.

Engineers select materials (typically medical‑grade plastics and stainless steel), design injection needles to minimize pain, and calibrate the mechanism to deliver accurate volumes. Safety features—such as needle shields that retract after injection—prevent accidental injury. Each batch undergoes mechanical testing to ensure consistent force and volume delivery.

Innovating Transdermal Gels and Patches

Transdermal systems remain popular for testosterone delivery, and breakthroughs in polymer science and adhesive technology have improved their performance. Manufacturers create gels by dissolving testosterone in a solvent with penetration enhancers and gelling agents. The mixture is homogenized and filled into single‑dose packets or metered pumps. Patches consist of several layers: a backing film, a reservoir or matrix containing the hormone, a rate‑controlling membrane and an adhesive layer. Engineers optimize the polymer blend to balance permeability (so the hormone diffuses at the right rate) and adhesion (so the patch stays on but peels off without irritation). Advances such as microemulsion gels and novel adhesives reduce transfer risk and skin irritation.

Telehealth Platforms: Building the Digital Infrastructure

Behind the convenience of telemedicine lies a complex web of software and logistics. Telehealth platforms that offer TRT services integrate electronic medical records, video conferencing, prescription management and pharmacy fulfillment. Developers design secure portals for patients to book appointments, complete symptom questionnaires and upload lab results. The system must comply with HIPAA and other regulations to protect privacy.

Pharmacy partners then package medications, coordinate shipping and track inventory. At‑home lab kits are manufactured under controlled conditions; they include lancets, blood collection tubes and instructions for use. Logistics teams handle return shipping, and laboratories process samples with high‑throughput analyzers. All of these steps require coordination between software engineers, clinicians, pharmacists and couriers.

Gene‑Editing and Cell Engineering: Future Horizons

Beyond AAV gene therapy, researchers are exploring CRISPR‑based gene editing to correct mutations responsible for hypogonadism. This involves designing guide RNA molecules specific to defective genes and delivering them with Cas enzymes to stem cells or directly into testicular tissue. Although not yet in clinical use, companies are developing manufacturing pipelines for CRISPR reagents and ex vivo edited cells, which would be expanded in culture and then transplanted. Such therapies require specialized clean rooms, genome sequencing to verify editing accuracy and long‑term safety studies.

Another frontier is laboratory‑grown Leydig cells derived from induced pluripotent stem cells (iPSCs). In university laboratories, scientists reprogram skin or blood cells into pluripotent stem cells and then coax them into testosterone‑producing Leydig‑like cells using specific growth factors and 3D culture systems. Once perfected, these cells could be transplanted into patients or used to create bioartificial testicular implants. Manufacturing these therapies at scale would demand bioreactors, differentiation protocols and rigorous quality testing to ensure hormonal function and safety.

Conclusion

Modern testosterone replacement therapy is the result of intricate engineering and biomanufacturing. New delivery systems like hydrogel microbeads rely on fully aqueous encapsulation to avoid oil residues and achieve slow, steady hormone release. 3D‑printed microbeads use drop‑on‑demand technology to produce customizable spheres from alginate and liposomes. Oral testosterone softgels employ lipid‑based systems to bypass the liver and achieve high bioavailability. Gene therapy vectors are manufactured in sophisticated cell factories using transient transfection or baculovirus systems and then purified through chromatography. AI algorithms are trained on patient data to tailor dosing and integrate continuous inputs from wearables. Meanwhile, advances in transdermal formulations, microdosing injectors, telehealth infrastructure, and regenerative medicine reflect a holistic approach to hormone care.

Understanding how these breakthrough tools are made highlights the complexity and precision required to deliver safe and effective therapy. Patients can appreciate that behind every convenient gel packet or telehealth appointment lies a global network of scientists, engineers and clinicians working to revolutionize testosterone care. As technology continues to evolve, the future of TRT promises even more personalized, sustainable and transformative solutions.

Frequently Asked Questions (FAQs)

What makes hydrogel microbeads safer than traditional microbeads?

 Traditional microbeads were formed using oil emulsions that left non‑biocompatible residues. The Core‑Shell Spherification process is fully aqueous, avoiding oil and producing biocompatible microbeads that slowly degrade and release hormone. This reduces tissue irritation and makes the beads easier to manufacture at scale.

How does drop‑on‑demand printing create microbeads?

 Researchers mix a printable hydrogel ink (such as alginate with drug‑loaded liposomes) and then use an electromagnetically controlled printhead to jet individual droplets into a cross‑linking bath. By adjusting pressure, nozzle diameter and actuation time, they create uniform beads on demand. This method offers precise control over bead size and structure.

Are oral testosterone capsules now effective?

 Yes. New formulations like testosterone undecanoate (Kyzatrex) use a lipid‑based system that bypasses the liver and is absorbed via the lymphatic system, providing approximately 90 % bioavailability. This allows oral capsules to maintain normal testosterone levels without liver toxicity.

How are gene therapy vectors manufactured for testosterone replacement?

 AAV vectors are produced in cell lines using either transient transfection of plasmids, infection with recombinant viruses, or baculovirus systems. Cells are grown in large bioreactors, transfected or infected with the necessary genes, and then harvested. The vectors are purified using chromatography to remove host cell proteins and empty capsids. Strict quality control ensures safety and potency before clinical use.

What role does artificial intelligence play in modern TRT?

 AI algorithms analyze patient data—including hormone levels, genetics, lifestyle and real‑time biometrics—to recommend personalized doses and adjust therapy dynamically. AI helps clinicians reduce trial‑and‑error, maintain steady hormone levels and improve adherence. Human oversight and robust data privacy measures ensure safe implementation.

Why are microdosing injectors considered innovative?

 Microdosing injectors deliver small amounts of testosterone more frequently, mimicking natural hormone rhythms and reducing peaks and troughs. Modern auto‑injector devices are engineered for precision, ease of use and safety, often integrating digital reminders and data logging. They must undergo rigorous mechanical and sterility testing to ensure reliability.

What is the future of TRT manufacturing?

 Future innovations may include gene‑editing therapies (using CRISPR) that permanently correct genetic causes of hypogonadism, laboratory‑grown Leydig cells for transplantation, and smart implants that release hormones on demand. Advances in AI, telehealth and regenerative medicine will likely make TRT more personalized, convenient and integrated with overall health monitoring.

How can patients ensure they are receiving high‑quality TRT products?

 Patients should work with licensed healthcare providers who prescribe FDA‑approved therapies. They can ask about the manufacturing processes, certifications and clinical evidence behind products. Reputable clinics monitor hormone levels, hematocrit and PSA regularly and adjust therapy as needed to maximize benefits and minimize risks.