Report on the Application of High-Density Polyethylene (HDPE) Raw Material in Gynecological Drug Delivery Devices

1. Core Physical and Chemical Properties and Safety Characteristics of HDPE Raw Materials

(1) Basic Physical and Chemical Properties

HDPE is formed by the polymerization of ethylene, with its molecular structure consisting only of carbon and hydrogen elements. It is odorless, tasteless, and non-toxic. Its density ranges from 0.941 to 0.965 g/cm³, with a crystallinity of 80% to 90%. Its melting point is approximately 131°C. It has high rigidity and excellent impact resistance, with a tensile strength of 20–35 MPa. Its temperature range is -40°C to 120°C, and it can be sterilized using ethylene oxide (EO) or gamma rays, maintaining stable performance without aging or deformation after sterilization. Additionally, HDPE has excellent barrier properties, with low permeability to water vapor and air, effectively preventing external contamination and protecting the active ingredients of the drugs.

(2) Biological Safety (Core Compatibility)

The gynecological drug delivery device must come into direct contact with the vaginal mucosa. The material must meet the requirements of being non-irritating, non-allergenic, and non-cytotoxic. HDPE is chemically very stable and does not undergo chemical reactions when in contact with mucous membranes or body fluids, nor does it release harmful substances such as heavy metals or plasticizers. It passes ISO 10993 and GB 16886 medical device biocompatibility tests and is a USP Class VI medical-grade certified material, serving as a negative control material for biocompatibility tests. In cell toxicity tests, the extract of HDPE has a relative proliferation rate of ≥70% for L929 cells; the skin irritation and sensitization tests show no redness, edema, or allergic reactions, fully adapting to the sensitive contact scenarios of the vaginal mucosa.

(3) Chemical Stability (Key to Drug Effect Assurance)

Gynecological drugs often contain components such as acylated proteins, carbopol, glycerol, etc., with some drugs having a pH value of 3.5–6.5, being weakly acidic. HDPE is resistant to acids, alkalis, oils, and chemical corrosion, does not react with drug components, and has no risk of adsorbing drugs or releasing impurities, maintaining the pH value and activity stability of the drug solution and avoiding drug efficacy degradation or deterioration. At the same time, HDPE has low hygroscopicity (water absorption rate < 0.01%), preventing the drug from becoming damp and clumping, and is suitable for multi-form drug delivery requirements such as gels and suppositories.

2. Application Advantages of HDPE in Gynecological Drug Delivery Devices

(1) Structural Adaptability: Balancing Rigidity and Comfort

Gynecological drug delivery devices must meet the requirements of "easy insertion, no damage to the mucosa, smooth injection". HDPE has an appropriate hardness, which can be molded into thin-walled smooth tubes (with a wall thickness tolerance of ±0.05 mm). The tube body has no burrs or sharp corners, and there is no pain during insertion, without damaging the fragile mucosa. It also has certain toughness, is not prone to breaking when bent, and is suitable for the vaginal physiological curve, enhancing the comfort of use. Additionally, HDPE can be processed into components such as the outer tube of the pusher, the push rod, and the protective cap, with strong structural integrity and no risk of loosening and leakage.

(2) Processing and Cost Advantages: Adapted for One-time Large-scale Production

The melt index of HDPE (for medical grade ≤ 0.5 g/10 min) is moderate, with excellent injection and extrusion molding performance, enabling high-precision and high-efficiency production. It is suitable for the large-scale requirements of one-time drug delivery devices. Compared to glass and PP materials, HDPE is lightweight (weight reduced by more than 60% compared to glass), resistant to drops and damage, has no risk of damage during transportation and storage, and is inexpensive, reducing the production cost of one-time consumables, alleviating the burden on patients, and aligning with the development direction of medical consumables "safety, economy, and convenience".

(3) Sterilization and Compliance Adaptability: Meeting Medical Grade Quality Control Requirements

HDPE can withstand ethylene oxide (EO) sterilization (common sterilization methods), with no residues after sterilization and no release of harmful substances, meeting medical device standards such as YY/T 0969 and GB/T 16886. Meanwhile, the raw material of HDPE is traceable, and the impurity content can be controlled (heavy metal lead ≤ 1 ppm, cadmium ≤ 0.5 ppm), the microbial limit is ≤ 100 CFU / piece, the bacterial endotoxin is < 0.25 EU/mL, meeting the requirements of NMPA medical device filing and GMP production standards. Currently, the mainstream anti-HPV dressings and gynecological gel applicators in the market all use HDPE materials, and their clinical application safety records are good.

(4) Environmental advantages: Recyclable to reduce medical pollution

HDPE is a #2 recyclable code material, with a recycling rate exceeding 75%. After disposal, it can be recycled and reprocessed, without the risk of white pollution, and complies with the EU one-time plastic directive and domestic medical environmental protection policies. Compared with materials such as PVC (containing plasticizers and difficult to degrade), the disposal of HDPE is safer, and it is suitable for harmless treatment of medical waste.

3. Key points of quality control (compliance core)

(1) Raw material selection: Strictly select medical-grade HDPE

It is necessary to use medical-grade HDPE resin, in accordance with GB/T 11115 and YBB 0001 standards, and provide an inspection report for raw materials at the factory (including melt index, density, heavy metals, microorganisms, etc.). It is strictly prohibited to add recycled materials, plasticizers, stabilizers, etc., to avoid the migration of impurities and trigger safety risks.

(2) Production process: Clean environment and process control

The production environment needs to reach a 100,000-level clean workshop to avoid microbial contamination during the production process. The injection molding temperature is controlled at 180–220℃ to prevent material degradation; the wall thickness of the tube is uniform, without bubbles, cracks, or burrs; the component assembly is tight, the push rod injection is smooth, and there is no jamming, ensuring the accurate dosage of drug administration.

(3) Finished product testing: Comprehensive biological and chemical verification

The finished product needs to pass dissolution tests (65% ethanol, n-hexane, purified water medium, monitoring heavy metals, oxidizable substances), cell toxicity tests, mucosal irritation tests, sterilization verification (epoxyethane residue < 10 μg/g), etc. Only after passing these tests can it be launched. At the same time, each batch of finished products needs to be retained for testing, and a full life cycle quality traceability system needs to be established.

4. Industry application status and cases

At present, HDPE has occupied more than 80% of the market share of gynecological drug delivery device raw materials, becoming the industry's preferred material. Typical application cases are as follows:

Anti-HPV functional gynecological dressing applicator: Using HDPE material, consisting of an outer tube, push rod, and protective cap, suitable for 5g gel drug delivery, the biological compatibility and chemical stability meet clinical requirements, and has been filed as a medical device.

Vaginal irrigator: HDPE material is integrated molding, the bottle body is soft and easy to squeeze, the water outlet is smooth, suitable for dilute drug liquid irrigation, without mucosal irritation risk, widely used in vaginal inflammation auxiliary treatment.

Vaginal suppository drug delivery applicator: HDPE hard tube body, precise positioning for drug delivery depth, preventing suppository detachment, the material does not react with the suppository base, ensuring stable drug efficacy.

5. Conclusion and outlook

High-density polyethylene (HDPE) with excellent biological safety, chemical stability, processing adaptability, and environmental economic benefits perfectly suits the application scenarios and quality control requirements of gynecological drug delivery devices. It is currently the most ideal raw material choice, providing a safe, reliable, and convenient drug delivery solution for female gynecological diseases treatment.

In the future, with the development of medical material technology, HDPE will upgrade to higher purity and functionalization, such as antibacterial modification, transparent modification, etc., further improving the safety and usage experience of drug delivery devices; at the same time, the industry needs to continuously strengthen raw material traceability, production control, and finished product testing, strictly following medical device regulations to ensure product quality and patient medication safety.